From b63e502f34bcdac5971d571ff4587c8d886ce384 Mon Sep 17 00:00:00 2001
From: Nadir Seghir <nadir.seghir@gmail.com>
Date: Wed, 27 Oct 2021 12:26:30 +0100
Subject: [PATCH 01/17] add min and step to Store API

---
 bin/hook-docs/data/filters.json         | 54 ++++++++++++++++++++++++
 docs/extensibility/filters.md           | 56 +++++++++++++++++++++++++
 src/StoreApi/Schemas/CartItemSchema.php | 46 ++++++++++++++++++++
 3 files changed, 156 insertions(+)

diff --git a/bin/hook-docs/data/filters.json b/bin/hook-docs/data/filters.json
index 7c319bbd862..9b3f3a9e24a 100644
--- a/bin/hook-docs/data/filters.json
+++ b/bin/hook-docs/data/filters.json
@@ -814,6 +814,60 @@
             },
             "args": 1
         },
+        {
+            "name": "woocommerce_store_api_item_quantity_increment",
+            "file": "StoreApi/Schemas/CartItemSchema.php",
+            "type": "filter",
+            "doc": {
+                "description": "Filters the quantity increment for a cart item in Store API.",
+                "long_description": "",
+                "tags": [
+                    {
+                        "name": "param",
+                        "content": "Cart item array.",
+                        "types": [
+                            "array"
+                        ],
+                        "variable": "$cart_item"
+                    },
+                    {
+                        "name": "return",
+                        "content": "",
+                        "types": [
+                            "\\Automattic\\WooCommerce\\Blocks\\StoreApi\\Schemas\\number"
+                        ]
+                    }
+                ],
+                "long_description_html": ""
+            }
+        },
+        {
+            "name": "woocommerce_store_api_item_quantity_minimum",
+            "file": "StoreApi/Schemas/CartItemSchema.php",
+            "type": "filter",
+            "doc": {
+                "description": "Filters the quantity minimum for a cart item in Store API.",
+                "long_description": "",
+                "tags": [
+                    {
+                        "name": "param",
+                        "content": "Cart item array.",
+                        "types": [
+                            "array"
+                        ],
+                        "variable": "$cart_item"
+                    },
+                    {
+                        "name": "return",
+                        "content": "",
+                        "types": [
+                            "\\Automattic\\WooCommerce\\Blocks\\StoreApi\\Schemas\\number"
+                        ]
+                    }
+                ],
+                "long_description_html": ""
+            }
+        },
         {
             "name": "woocommerce_store_api_product_quantity_limit",
             "file": "StoreApi/Schemas/ProductSchema.php",
diff --git a/docs/extensibility/filters.md b/docs/extensibility/filters.md
index 4a47c98f11c..5b13fb42a49 100644
--- a/docs/extensibility/filters.md
+++ b/docs/extensibility/filters.md
@@ -29,6 +29,8 @@
  - [woocommerce_shipping_package_name](#woocommerce_shipping_package_name)
  - [woocommerce_show_page_title](#woocommerce_show_page_title)
  - [woocommerce_store_api_disable_nonce_check](#woocommerce_store_api_disable_nonce_check)
+ - [woocommerce_store_api_item_quantity_increment](#woocommerce_store_api_item_quantity_increment)
+ - [woocommerce_store_api_item_quantity_minimum](#woocommerce_store_api_item_quantity_minimum)
  - [woocommerce_store_api_product_quantity_limit](#woocommerce_store_api_product_quantity_limit)
  - [woocommerce_variation_option_name](#woocommerce_variation_option_name)
 
@@ -692,6 +694,60 @@ apply_filters( 'woocommerce_store_api_disable_nonce_check', boolean $disable_non
 
 ---
 
+## woocommerce_store_api_item_quantity_increment
+
+
+Filters the quantity increment for a cart item in Store API.
+
+```php
+apply_filters( 'woocommerce_store_api_item_quantity_increment', array $cart_item )
+```
+
+### Parameters
+
+| Argument | Type | Description |
+| -------- | ---- | ----------- |
+| $cart_item | array | Cart item array. |
+
+### Returns
+
+
+`\Automattic\WooCommerce\Blocks\StoreApi\Schemas\number` 
+
+### Source
+
+
+File: [StoreApi/Schemas/CartItemSchema.php](../src/StoreApi/Schemas/CartItemSchema.php)
+
+---
+
+## woocommerce_store_api_item_quantity_minimum
+
+
+Filters the quantity minimum for a cart item in Store API.
+
+```php
+apply_filters( 'woocommerce_store_api_item_quantity_minimum', array $cart_item )
+```
+
+### Parameters
+
+| Argument | Type | Description |
+| -------- | ---- | ----------- |
+| $cart_item | array | Cart item array. |
+
+### Returns
+
+
+`\Automattic\WooCommerce\Blocks\StoreApi\Schemas\number` 
+
+### Source
+
+
+File: [StoreApi/Schemas/CartItemSchema.php](../src/StoreApi/Schemas/CartItemSchema.php)
+
+---
+
 ## woocommerce_store_api_product_quantity_limit
 
 
diff --git a/src/StoreApi/Schemas/CartItemSchema.php b/src/StoreApi/Schemas/CartItemSchema.php
index f384d970dff..c431735e50c 100644
--- a/src/StoreApi/Schemas/CartItemSchema.php
+++ b/src/StoreApi/Schemas/CartItemSchema.php
@@ -57,6 +57,18 @@ public function get_properties() {
 				'context'     => [ 'view', 'edit' ],
 				'readonly'    => true,
 			],
+			'quantity_min'         => [
+				'description' => __( 'The minimum quantity than can be added to the cart at once.', 'woo-gutenberg-products-block' ),
+				'type'        => 'integer',
+				'context'     => [ 'view', 'edit' ],
+				'readonly'    => true,
+			],
+			'quantity_increment'   => [
+				'description' => __( 'The amount quantity can change with.', 'woo-gutenberg-products-block' ),
+				'type'        => 'integer',
+				'context'     => [ 'view', 'edit' ],
+				'readonly'    => true,
+			],
 			'name'                 => [
 				'description' => __( 'Product name.', 'woo-gutenberg-products-block' ),
 				'type'        => 'string',
@@ -314,6 +326,8 @@ public function get_item_response( $cart_item ) {
 			'id'                   => $product->get_id(),
 			'quantity'             => wc_stock_amount( $cart_item['quantity'] ),
 			'quantity_limit'       => $this->get_product_quantity_limit( $product ),
+			'quantity_min'         => $this->get_item_quantity_min( $cart_item ),
+			'quantity_increment'   => $this->get_item_quantity_increment( $cart_item ),
 			'name'                 => $this->prepare_html_response( $product->get_title() ),
 			'short_description'    => $this->prepare_html_response( wc_format_content( wp_kses_post( $product->get_short_description() ) ) ),
 			'description'          => $this->prepare_html_response( wc_format_content( wp_kses_post( $product->get_description() ) ) ),
@@ -451,6 +465,38 @@ protected function get_item_data( $cart_item ) {
 		return array_map( [ $this, 'format_item_data_element' ], $item_data );
 	}
 
+	/**
+	 * Return the minimum quantity that's allowed for this item.
+	 *
+	 * @param array $cart_item Cart item array.
+	 * @return number
+	 */
+	protected function get_item_quantity_min( $cart_item ) {
+		/**
+		 * Filters the quantity minimum for a cart item in Store API.
+		 *
+		 * @param array $cart_item Cart item array.
+		 * @return number
+		 */
+		return apply_filters( 'woocommerce_store_api_item_quantity_minimum', 1, $cart_item );
+	}
+
+	/**
+	 * Return the increment quantity that an item is allowed to change with.
+	 *
+	 * @param array $cart_item Cart item array.
+	 * @return number
+	 */
+	protected function get_item_quantity_increment( $cart_item ) {
+		/**
+		 * Filters the quantity increment for a cart item in Store API.
+		 *
+		 * @param array $cart_item Cart item array.
+		 * @return number
+		 */
+		return apply_filters( 'woocommerce_store_api_item_quantity_increment', 1, $cart_item );
+	}
+
 	/**
 	 * Remove HTML tags from cart item data and set the `hidden` property to
 	 * `__experimental_woocommerce_blocks_hidden`.

From 6ecec1f6301f594cb92c41a5728177a6dbd6a226 Mon Sep 17 00:00:00 2001
From: Nadir Seghir <nadir.seghir@gmail.com>
Date: Thu, 28 Oct 2021 17:50:03 +0100
Subject: [PATCH 02/17] add min and step support

---
 .../components/quantity-selector/index.tsx    | 80 ++++++++++++++-----
 .../cart-line-item-row.tsx                    |  4 +
 assets/js/types/type-defs/cart.ts             |  2 +
 bin/hook-docs/data/filters.json               |  8 +-
 docs/extensibility/filters.md                 | 14 ++--
 src/StoreApi/Schemas/CartItemSchema.php       |  6 +-
 6 files changed, 82 insertions(+), 32 deletions(-)

diff --git a/assets/js/base/components/quantity-selector/index.tsx b/assets/js/base/components/quantity-selector/index.tsx
index 516740236c4..b2a0c250de0 100644
--- a/assets/js/base/components/quantity-selector/index.tsx
+++ b/assets/js/base/components/quantity-selector/index.tsx
@@ -6,6 +6,7 @@ import { speak } from '@wordpress/a11y';
 import classNames from 'classnames';
 import { useCallback } from '@wordpress/element';
 import { DOWN, UP } from '@wordpress/keycodes';
+import useDebouncedCallback from 'use-debounce/lib/useDebouncedCallback';
 
 /**
  * Internal dependencies
@@ -31,6 +32,10 @@ export interface QuantitySelectorProps {
 	 * Maximum quantity
 	 */
 	maximum: number;
+	/**
+	 * Input step attribute.
+	 */
+	step?: number;
 	/**
 	 * Event handler triggered when the quantity is changed
 	 */
@@ -53,6 +58,7 @@ const QuantitySelector = ( {
 	minimum = 1,
 	maximum,
 	onChange = () => void 0,
+	step = 1,
 	itemName = '',
 	disabled,
 }: QuantitySelectorProps ): JSX.Element => {
@@ -62,8 +68,46 @@ const QuantitySelector = ( {
 	);
 
 	const hasMaximum = typeof maximum !== 'undefined';
-	const canDecrease = quantity > minimum;
-	const canIncrease = ! hasMaximum || quantity < maximum;
+	const canDecrease = quantity - step > minimum;
+	const canIncrease = ! hasMaximum || quantity + step < maximum;
+
+	/**
+	 * The goal of this function is to normalize what was inserted,
+	 * but after the customer has stopped typing.
+	 *
+	 * It's important to wait before normalizing or we end up with
+	 * a frustrating expiernce, for example, if the minimun is 2 and
+	 * the customer is trying to type "10", premature normalizing would
+	 * always kick in at "1" and turn that into 2.
+	 */
+	const [ normalizeQuantity ] = useDebouncedCallback(
+		( initialValue: number ) => {
+			// We copy the starting value.
+			let value = initialValue;
+
+			// We check if we have a maximum value, and select the lowest between what was inserted, and the maximum.
+			if ( hasMaximum ) {
+				value = Math.min(
+					value,
+					// the maximum possible value in step increments.
+					Math.floor( maximum / step ) * step
+				);
+			}
+
+			// Select the biggest between what's inserted, the the minimum value in steps.
+			value = Math.max( value, Math.ceil( minimum / step ) * step );
+
+			// We round off the value to our steps.
+			value = Math.floor( value / step ) * step;
+
+			// Only commit if the value has changed
+			if ( value !== initialValue ) {
+				onChange( value );
+			}
+		},
+		// This value is delibrtly smaller than what's in useStoreCartItemQuantity so we don't end up with two requests.
+		300
+	);
 
 	/**
 	 * Handles keyboard up and down keys to change quantity value.
@@ -83,15 +127,15 @@ const QuantitySelector = ( {
 
 			if ( isArrowDown && canDecrease ) {
 				event.preventDefault();
-				onChange( quantity - 1 );
+				onChange( quantity - step );
 			}
 
 			if ( isArrowUp && canIncrease ) {
 				event.preventDefault();
-				onChange( quantity + 1 );
+				onChange( quantity + step );
 			}
 		},
-		[ quantity, onChange, canIncrease, canDecrease ]
+		[ quantity, onChange, canIncrease, canDecrease, step ]
 	);
 
 	return (
@@ -100,22 +144,22 @@ const QuantitySelector = ( {
 				className="wc-block-components-quantity-selector__input"
 				disabled={ disabled }
 				type="number"
-				step="1"
-				min="0"
+				step={ step }
+				min={ minimum }
 				value={ quantity }
 				onKeyDown={ quantityInputOnKeyDown }
 				onChange={ ( event ) => {
-					let value =
-						Number.isNaN( event.target.value ) ||
-						! event.target.value
-							? 0
-							: parseInt( event.target.value, 10 );
-					if ( hasMaximum ) {
-						value = Math.min( value, maximum );
-					}
-					value = Math.max( value, minimum );
+					// Inputs values are strings, we parse them here.
+					let value = parseInt( event.target.value, 10 );
+					// parseInt would throw NaN for anything not a number,
+					// so we revert value to the quantity value.
+					value = isNaN( value ) ? quantity : value;
+
 					if ( value !== quantity ) {
+						// we commit this value immideatly.
 						onChange( value );
+						// but once the customer has stopped typing, we make sure his value is respecting the bounds (maximum value, minimum value, step value), and commit the normlized value.
+						normalizeQuantity( value );
 					}
 				} }
 				aria-label={ sprintf(
@@ -135,7 +179,7 @@ const QuantitySelector = ( {
 				className="wc-block-components-quantity-selector__button wc-block-components-quantity-selector__button--minus"
 				disabled={ disabled || ! canDecrease }
 				onClick={ () => {
-					const newQuantity = quantity - 1;
+					const newQuantity = quantity - step;
 					onChange( newQuantity );
 					speak(
 						sprintf(
@@ -159,7 +203,7 @@ const QuantitySelector = ( {
 				disabled={ disabled || ! canIncrease }
 				className="wc-block-components-quantity-selector__button wc-block-components-quantity-selector__button--plus"
 				onClick={ () => {
-					const newQuantity = quantity + 1;
+					const newQuantity = quantity + step;
 					onChange( newQuantity );
 					speak(
 						sprintf(
diff --git a/assets/js/blocks/cart-checkout/cart/cart-line-items-table/cart-line-item-row.tsx b/assets/js/blocks/cart-checkout/cart/cart-line-items-table/cart-line-item-row.tsx
index 94bc2b0e05d..b6b4c3ab27f 100644
--- a/assets/js/blocks/cart-checkout/cart/cart-line-items-table/cart-line-item-row.tsx
+++ b/assets/js/blocks/cart-checkout/cart/cart-line-items-table/cart-line-item-row.tsx
@@ -71,6 +71,8 @@ const CartLineItemRow = forwardRef< HTMLTableRowElement, CartLineItemRowProps >(
 			low_stock_remaining: lowStockRemaining = null,
 			show_backorder_badge: showBackorderBadge = false,
 			quantity_limit: quantityLimit = 99,
+			quantity_min: quantityMin = 1,
+			quantity_step: quantityStep = 1,
 			permalink = '',
 			images = [],
 			variation = [],
@@ -282,6 +284,8 @@ const CartLineItemRow = forwardRef< HTMLTableRowElement, CartLineItemRowProps >(
 							disabled={ isPendingDelete }
 							quantity={ quantity }
 							maximum={ quantityLimit }
+							minimum={ quantityMin }
+							step={ quantityStep }
 							onChange={ ( newQuantity ) => {
 								setItemQuantity( newQuantity );
 								dispatchStoreEvent( 'cart-set-item-quantity', {
diff --git a/assets/js/types/type-defs/cart.ts b/assets/js/types/type-defs/cart.ts
index 31d17c53fea..59b4c80c562 100644
--- a/assets/js/types/type-defs/cart.ts
+++ b/assets/js/types/type-defs/cart.ts
@@ -118,6 +118,8 @@ export interface CartItem {
 	quantity: number;
 	catalog_visibility: CatalogVisibility;
 	quantity_limit: number;
+	quantity_min: number;
+	quantity_step: number;
 	name: string;
 	summary: string;
 	short_description: string;
diff --git a/bin/hook-docs/data/filters.json b/bin/hook-docs/data/filters.json
index 9b3f3a9e24a..379eb2cacdf 100644
--- a/bin/hook-docs/data/filters.json
+++ b/bin/hook-docs/data/filters.json
@@ -815,11 +815,11 @@
             "args": 1
         },
         {
-            "name": "woocommerce_store_api_item_quantity_increment",
+            "name": "woocommerce_store_api_item_quantity_minimum",
             "file": "StoreApi/Schemas/CartItemSchema.php",
             "type": "filter",
             "doc": {
-                "description": "Filters the quantity increment for a cart item in Store API.",
+                "description": "Filters the quantity minimum for a cart item in Store API.",
                 "long_description": "",
                 "tags": [
                     {
@@ -842,11 +842,11 @@
             }
         },
         {
-            "name": "woocommerce_store_api_item_quantity_minimum",
+            "name": "woocommerce_store_api_item_quantity_step",
             "file": "StoreApi/Schemas/CartItemSchema.php",
             "type": "filter",
             "doc": {
-                "description": "Filters the quantity minimum for a cart item in Store API.",
+                "description": "Filters the quantity increment for a cart item in Store API.",
                 "long_description": "",
                 "tags": [
                     {
diff --git a/docs/extensibility/filters.md b/docs/extensibility/filters.md
index 5b13fb42a49..7a87746fbcf 100644
--- a/docs/extensibility/filters.md
+++ b/docs/extensibility/filters.md
@@ -29,8 +29,8 @@
  - [woocommerce_shipping_package_name](#woocommerce_shipping_package_name)
  - [woocommerce_show_page_title](#woocommerce_show_page_title)
  - [woocommerce_store_api_disable_nonce_check](#woocommerce_store_api_disable_nonce_check)
- - [woocommerce_store_api_item_quantity_increment](#woocommerce_store_api_item_quantity_increment)
  - [woocommerce_store_api_item_quantity_minimum](#woocommerce_store_api_item_quantity_minimum)
+ - [woocommerce_store_api_item_quantity_step](#woocommerce_store_api_item_quantity_step)
  - [woocommerce_store_api_product_quantity_limit](#woocommerce_store_api_product_quantity_limit)
  - [woocommerce_variation_option_name](#woocommerce_variation_option_name)
 
@@ -694,13 +694,13 @@ apply_filters( 'woocommerce_store_api_disable_nonce_check', boolean $disable_non
 
 ---
 
-## woocommerce_store_api_item_quantity_increment
+## woocommerce_store_api_item_quantity_minimum
 
 
-Filters the quantity increment for a cart item in Store API.
+Filters the quantity minimum for a cart item in Store API.
 
 ```php
-apply_filters( 'woocommerce_store_api_item_quantity_increment', array $cart_item )
+apply_filters( 'woocommerce_store_api_item_quantity_minimum', array $cart_item )
 ```
 
 ### Parameters
@@ -721,13 +721,13 @@ File: [StoreApi/Schemas/CartItemSchema.php](../src/StoreApi/Schemas/CartItemSche
 
 ---
 
-## woocommerce_store_api_item_quantity_minimum
+## woocommerce_store_api_item_quantity_step
 
 
-Filters the quantity minimum for a cart item in Store API.
+Filters the quantity increment for a cart item in Store API.
 
 ```php
-apply_filters( 'woocommerce_store_api_item_quantity_minimum', array $cart_item )
+apply_filters( 'woocommerce_store_api_item_quantity_step', array $cart_item )
 ```
 
 ### Parameters
diff --git a/src/StoreApi/Schemas/CartItemSchema.php b/src/StoreApi/Schemas/CartItemSchema.php
index c431735e50c..413fc871ef4 100644
--- a/src/StoreApi/Schemas/CartItemSchema.php
+++ b/src/StoreApi/Schemas/CartItemSchema.php
@@ -327,7 +327,7 @@ public function get_item_response( $cart_item ) {
 			'quantity'             => wc_stock_amount( $cart_item['quantity'] ),
 			'quantity_limit'       => $this->get_product_quantity_limit( $product ),
 			'quantity_min'         => $this->get_item_quantity_min( $cart_item ),
-			'quantity_increment'   => $this->get_item_quantity_increment( $cart_item ),
+			'quantity_step'        => $this->get_item_quantity_step( $cart_item ),
 			'name'                 => $this->prepare_html_response( $product->get_title() ),
 			'short_description'    => $this->prepare_html_response( wc_format_content( wp_kses_post( $product->get_short_description() ) ) ),
 			'description'          => $this->prepare_html_response( wc_format_content( wp_kses_post( $product->get_description() ) ) ),
@@ -487,14 +487,14 @@ protected function get_item_quantity_min( $cart_item ) {
 	 * @param array $cart_item Cart item array.
 	 * @return number
 	 */
-	protected function get_item_quantity_increment( $cart_item ) {
+	protected function get_item_quantity_step( $cart_item ) {
 		/**
 		 * Filters the quantity increment for a cart item in Store API.
 		 *
 		 * @param array $cart_item Cart item array.
 		 * @return number
 		 */
-		return apply_filters( 'woocommerce_store_api_item_quantity_increment', 1, $cart_item );
+		return apply_filters( 'woocommerce_store_api_item_quantity_step', 1, $cart_item );
 	}
 
 	/**

From 4058acd9979577766da05bed35ee0155292168c2 Mon Sep 17 00:00:00 2001
From: Nadir Seghir <nadir.seghir@gmail.com>
Date: Thu, 28 Oct 2021 19:09:56 +0100
Subject: [PATCH 03/17] typo

---
 src/StoreApi/Schemas/CartItemSchema.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/StoreApi/Schemas/CartItemSchema.php b/src/StoreApi/Schemas/CartItemSchema.php
index 413fc871ef4..7d54cb96398 100644
--- a/src/StoreApi/Schemas/CartItemSchema.php
+++ b/src/StoreApi/Schemas/CartItemSchema.php
@@ -63,7 +63,7 @@ public function get_properties() {
 				'context'     => [ 'view', 'edit' ],
 				'readonly'    => true,
 			],
-			'quantity_increment'   => [
+			'quantity_step'        => [
 				'description' => __( 'The amount quantity can change with.', 'woo-gutenberg-products-block' ),
 				'type'        => 'integer',
 				'context'     => [ 'view', 'edit' ],

From 5529eb0fe7aa3e1856c5a22391b4651292d8a15f Mon Sep 17 00:00:00 2001
From: Mike Jolley <mike.jolley@me.com>
Date: Wed, 15 Dec 2021 11:08:32 +0000
Subject: [PATCH 04/17] Update
 assets/js/base/components/quantity-selector/index.tsx

---
 assets/js/base/components/quantity-selector/index.tsx | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/assets/js/base/components/quantity-selector/index.tsx b/assets/js/base/components/quantity-selector/index.tsx
index b2a0c250de0..08117014c29 100644
--- a/assets/js/base/components/quantity-selector/index.tsx
+++ b/assets/js/base/components/quantity-selector/index.tsx
@@ -76,7 +76,7 @@ const QuantitySelector = ( {
 	 * but after the customer has stopped typing.
 	 *
 	 * It's important to wait before normalizing or we end up with
-	 * a frustrating expiernce, for example, if the minimun is 2 and
+	 * a frustrating experience, for example, if the minimum is 2 and
 	 * the customer is trying to type "10", premature normalizing would
 	 * always kick in at "1" and turn that into 2.
 	 */

From 512e6e8554c47be58ba67e265ae64604183fb7fd Mon Sep 17 00:00:00 2001
From: Mike Jolley <mike.jolley@me.com>
Date: Wed, 15 Dec 2021 11:08:39 +0000
Subject: [PATCH 05/17] Update
 assets/js/base/components/quantity-selector/index.tsx

---
 assets/js/base/components/quantity-selector/index.tsx | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/assets/js/base/components/quantity-selector/index.tsx b/assets/js/base/components/quantity-selector/index.tsx
index 08117014c29..57c849a0011 100644
--- a/assets/js/base/components/quantity-selector/index.tsx
+++ b/assets/js/base/components/quantity-selector/index.tsx
@@ -156,7 +156,7 @@ const QuantitySelector = ( {
 					value = isNaN( value ) ? quantity : value;
 
 					if ( value !== quantity ) {
-						// we commit this value immideatly.
+						// we commit this value immediately.
 						onChange( value );
 						// but once the customer has stopped typing, we make sure his value is respecting the bounds (maximum value, minimum value, step value), and commit the normlized value.
 						normalizeQuantity( value );

From f9b2119dbb47502b803e58f991c05739c753faaa Mon Sep 17 00:00:00 2001
From: Mike Jolley <mike.jolley@me.com>
Date: Wed, 15 Dec 2021 11:58:35 +0000
Subject: [PATCH 06/17] Fix debounce callback

---
 assets/js/base/components/quantity-selector/index.tsx | 6 +++---
 src/StoreApi/Schemas/CartItemSchema.php               | 3 +--
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/assets/js/base/components/quantity-selector/index.tsx b/assets/js/base/components/quantity-selector/index.tsx
index 57c849a0011..aa4b5e541be 100644
--- a/assets/js/base/components/quantity-selector/index.tsx
+++ b/assets/js/base/components/quantity-selector/index.tsx
@@ -6,7 +6,7 @@ import { speak } from '@wordpress/a11y';
 import classNames from 'classnames';
 import { useCallback } from '@wordpress/element';
 import { DOWN, UP } from '@wordpress/keycodes';
-import useDebouncedCallback from 'use-debounce/lib/useDebouncedCallback';
+import { useDebouncedCallback } from 'use-debounce';
 
 /**
  * Internal dependencies
@@ -80,7 +80,7 @@ const QuantitySelector = ( {
 	 * the customer is trying to type "10", premature normalizing would
 	 * always kick in at "1" and turn that into 2.
 	 */
-	const [ normalizeQuantity ] = useDebouncedCallback(
+	const normalizeQuantity = useDebouncedCallback(
 		( initialValue: number ) => {
 			// We copy the starting value.
 			let value = initialValue;
@@ -105,7 +105,7 @@ const QuantitySelector = ( {
 				onChange( value );
 			}
 		},
-		// This value is delibrtly smaller than what's in useStoreCartItemQuantity so we don't end up with two requests.
+		// This value is deliberately smaller than what's in useStoreCartItemQuantity so we don't end up with two requests.
 		300
 	);
 
diff --git a/src/StoreApi/Schemas/CartItemSchema.php b/src/StoreApi/Schemas/CartItemSchema.php
index 7d54cb96398..83580625cfe 100644
--- a/src/StoreApi/Schemas/CartItemSchema.php
+++ b/src/StoreApi/Schemas/CartItemSchema.php
@@ -498,8 +498,7 @@ protected function get_item_quantity_step( $cart_item ) {
 	}
 
 	/**
-	 * Remove HTML tags from cart item data and set the `hidden` property to
-	 * `__experimental_woocommerce_blocks_hidden`.
+	 * Remove HTML tags from cart item data and set the `hidden` property to `__experimental_woocommerce_blocks_hidden`.
 	 *
 	 * @param array $item_data_element Individual element of a cart item data.
 	 * @return array

From 835058af0ebd3d20391e858f5979d2125a2b2232 Mon Sep 17 00:00:00 2001
From: Mike Jolley <mike.jolley@me.com>
Date: Wed, 15 Dec 2021 15:16:29 +0000
Subject: [PATCH 07/17] Style qty input to show steps

---
 assets/js/base/components/quantity-selector/index.tsx  | 4 ++--
 assets/js/base/components/quantity-selector/style.scss | 6 ++++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/assets/js/base/components/quantity-selector/index.tsx b/assets/js/base/components/quantity-selector/index.tsx
index aa4b5e541be..fc37680cd9d 100644
--- a/assets/js/base/components/quantity-selector/index.tsx
+++ b/assets/js/base/components/quantity-selector/index.tsx
@@ -193,7 +193,7 @@ const QuantitySelector = ( {
 					);
 				} }
 			>
-				&#65293;
+				{ step === 1 || quantity < step ? `－` : quantity - step }
 			</button>
 			<button
 				aria-label={ __(
@@ -217,7 +217,7 @@ const QuantitySelector = ( {
 					);
 				} }
 			>
-				&#65291;
+				{ step === 1 ? '＋' : quantity + step }
 			</button>
 		</div>
 	);
diff --git a/assets/js/base/components/quantity-selector/style.scss b/assets/js/base/components/quantity-selector/style.scss
index 3a7095e9eea..a2ab45f775f 100644
--- a/assets/js/base/components/quantity-selector/style.scss
+++ b/assets/js/base/components/quantity-selector/style.scss
@@ -41,6 +41,7 @@
 		line-height: 1;
 		vertical-align: middle;
 		-moz-appearance: textfield;
+		font-weight: 600;
 
 		&:focus {
 			background: $gray-100;
@@ -70,11 +71,12 @@
 
 	.wc-block-components-quantity-selector__button {
 		@include reset-button;
-		@include font-size(regular);
+		@include font-size(regular, 0.9em);
 		min-width: 30px;
 		cursor: pointer;
-		color: $gray-900;
+		color: $gray-600;
 		font-style: normal;
+		font-weight: normal;
 		text-align: center;
 		text-decoration: none;
 

From 434931734acdb1424f9f6f024b1fa796b468ba70 Mon Sep 17 00:00:00 2001
From: Mike Jolley <mike.jolley@me.com>
Date: Wed, 15 Dec 2021 17:53:31 +0000
Subject: [PATCH 08/17] Implement quantity_limits in API

---
 .../components/quantity-selector/index.tsx    |   3 +-
 .../cart-line-item-row.tsx                    |  43 +++---
 src/StoreApi/Routes/CartAddItem.php           |  10 +-
 src/StoreApi/Schemas/CartItemSchema.php       | 131 +++++++++++-------
 4 files changed, 111 insertions(+), 76 deletions(-)

diff --git a/assets/js/base/components/quantity-selector/index.tsx b/assets/js/base/components/quantity-selector/index.tsx
index fc37680cd9d..94d3ca7a61b 100644
--- a/assets/js/base/components/quantity-selector/index.tsx
+++ b/assets/js/base/components/quantity-selector/index.tsx
@@ -69,7 +69,7 @@ const QuantitySelector = ( {
 
 	const hasMaximum = typeof maximum !== 'undefined';
 	const canDecrease = quantity - step > minimum;
-	const canIncrease = ! hasMaximum || quantity + step < maximum;
+	const canIncrease = ! hasMaximum || quantity + step <= maximum;
 
 	/**
 	 * The goal of this function is to normalize what was inserted,
@@ -146,6 +146,7 @@ const QuantitySelector = ( {
 				type="number"
 				step={ step }
 				min={ minimum }
+				max={ maximum }
 				value={ quantity }
 				onKeyDown={ quantityInputOnKeyDown }
 				onChange={ ( event ) => {
diff --git a/assets/js/blocks/cart-checkout/cart/cart-line-items-table/cart-line-item-row.tsx b/assets/js/blocks/cart-checkout/cart/cart-line-items-table/cart-line-item-row.tsx
index b6b4c3ab27f..8c1fa5445bc 100644
--- a/assets/js/blocks/cart-checkout/cart/cart-line-items-table/cart-line-item-row.tsx
+++ b/assets/js/blocks/cart-checkout/cart/cart-line-items-table/cart-line-item-row.tsx
@@ -70,9 +70,11 @@ const CartLineItemRow = forwardRef< HTMLTableRowElement, CartLineItemRowProps >(
 			description: fullDescription = '',
 			low_stock_remaining: lowStockRemaining = null,
 			show_backorder_badge: showBackorderBadge = false,
-			quantity_limit: quantityLimit = 99,
-			quantity_min: quantityMin = 1,
-			quantity_step: quantityStep = 1,
+			quantity_limits: quantityLimits = {
+				minimum: 1,
+				maximum: 99,
+				multipleOf: 1,
+			},
 			permalink = '',
 			images = [],
 			variation = [],
@@ -280,21 +282,26 @@ const CartLineItemRow = forwardRef< HTMLTableRowElement, CartLineItemRowProps >(
 					/>
 
 					<div className="wc-block-cart-item__quantity">
-						<QuantitySelector
-							disabled={ isPendingDelete }
-							quantity={ quantity }
-							maximum={ quantityLimit }
-							minimum={ quantityMin }
-							step={ quantityStep }
-							onChange={ ( newQuantity ) => {
-								setItemQuantity( newQuantity );
-								dispatchStoreEvent( 'cart-set-item-quantity', {
-									product: lineItem,
-									quantity: newQuantity,
-								} );
-							} }
-							itemName={ name }
-						/>
+						{ !! quantityLimits && (
+							<QuantitySelector
+								disabled={ isPendingDelete }
+								quantity={ quantity }
+								minimum={ quantityLimits.minimum }
+								maximum={ quantityLimits.maximum }
+								step={ quantityLimits.multipleOf }
+								onChange={ ( newQuantity ) => {
+									setItemQuantity( newQuantity );
+									dispatchStoreEvent(
+										'cart-set-item-quantity',
+										{
+											product: lineItem,
+											quantity: newQuantity,
+										}
+									);
+								} }
+								itemName={ name }
+							/>
+						) }
 						<button
 							className="wc-block-cart-item__remove-link"
 							onClick={ () => {
diff --git a/src/StoreApi/Routes/CartAddItem.php b/src/StoreApi/Routes/CartAddItem.php
index 113a9b7e536..074c3f2d192 100644
--- a/src/StoreApi/Routes/CartAddItem.php
+++ b/src/StoreApi/Routes/CartAddItem.php
@@ -29,12 +29,10 @@ public function get_args() {
 				'permission_callback' => '__return_true',
 				'args'                => [
 					'id'        => [
-						'description' => __( 'The cart item product or variation ID.', 'woo-gutenberg-products-block' ),
-						'type'        => 'integer',
-						'context'     => [ 'view', 'edit' ],
-						'arg_options' => [
-							'sanitize_callback' => 'absint',
-						],
+						'description'       => __( 'The cart item product or variation ID.', 'woo-gutenberg-products-block' ),
+						'type'              => 'integer',
+						'context'           => [ 'view', 'edit' ],
+						'sanitize_callback' => 'absint',
 					],
 					'quantity'  => [
 						'description' => __( 'Quantity of this item in the cart.', 'woo-gutenberg-products-block' ),
diff --git a/src/StoreApi/Schemas/CartItemSchema.php b/src/StoreApi/Schemas/CartItemSchema.php
index 83580625cfe..17213e59e04 100644
--- a/src/StoreApi/Schemas/CartItemSchema.php
+++ b/src/StoreApi/Schemas/CartItemSchema.php
@@ -47,27 +47,36 @@ public function get_properties() {
 			],
 			'quantity'             => [
 				'description' => __( 'Quantity of this item in the cart.', 'woo-gutenberg-products-block' ),
-				'type'        => 'integer',
-				'context'     => [ 'view', 'edit' ],
-				'readonly'    => true,
-			],
-			'quantity_limit'       => [
-				'description' => __( 'The maximum quantity than can be added to the cart at once.', 'woo-gutenberg-products-block' ),
-				'type'        => 'integer',
-				'context'     => [ 'view', 'edit' ],
-				'readonly'    => true,
-			],
-			'quantity_min'         => [
-				'description' => __( 'The minimum quantity than can be added to the cart at once.', 'woo-gutenberg-products-block' ),
-				'type'        => 'integer',
+				'type'        => 'number',
 				'context'     => [ 'view', 'edit' ],
 				'readonly'    => true,
 			],
-			'quantity_step'        => [
-				'description' => __( 'The amount quantity can change with.', 'woo-gutenberg-products-block' ),
-				'type'        => 'integer',
+			'quantity_limits'      => [
+				'description' => __( 'How the quantity of this item should be controlled, for example, any limits in place. This returns false if the input is disabled.', 'woo-gutenberg-products-block' ),
+				'type'        => [ 'object', 'boolean' ],
 				'context'     => [ 'view', 'edit' ],
 				'readonly'    => true,
+				'properties'  => [
+					'minimum'    => [
+						'description' => __( 'The minimum quantity allowed in the cart for this line item.', 'woo-gutenberg-products-block' ),
+						'type'        => 'integer',
+						'context'     => [ 'view', 'edit' ],
+						'readonly'    => true,
+					],
+					'maximum'    => [
+						'description' => __( 'The maximum quantity allowed in the cart for this line item.', 'woo-gutenberg-products-block' ),
+						'type'        => 'integer',
+						'context'     => [ 'view', 'edit' ],
+						'readonly'    => true,
+					],
+					'multipleOf' => [
+						'description' => __( 'The amount that quantities increment by. Quantity must be an increment of this value.', 'woo-gutenberg-products-block' ),
+						'type'        => 'integer',
+						'context'     => [ 'view', 'edit' ],
+						'readonly'    => true,
+						'default'     => 1,
+					],
+				],
 			],
 			'name'                 => [
 				'description' => __( 'Product name.', 'woo-gutenberg-products-block' ),
@@ -312,6 +321,60 @@ public function get_properties() {
 		];
 	}
 
+	/**
+	 * Return quantity limits e.g. min, max, and allowed multiples.
+	 *
+	 * @param array $cart_item Cart item array.
+	 * @return object|boolean
+	 */
+	protected function get_quantity_limits( $cart_item ) {
+		$product = $cart_item['data'];
+
+		/**
+		* Filters the quantity input for a cart item in Store API.
+		*
+		* @param array $product Product being added/updated in the cart.
+		* @return number
+		*/
+		$disabled = apply_filters( 'woocommerce_store_api_cart_item_quantity_disabled', $product->is_sold_individually(), $cart_item );
+
+		if ( $disabled ) {
+			return false;
+		}
+
+		$remaining_stock = $this->get_remaining_stock( $product );
+
+		/**
+		* Filters the quantity minimum for a cart item in Store API.
+		*
+		* @param array $product Product being added/updated in the cart.
+		* @return number
+		*/
+		$minimum = (int) apply_filters( 'woocommerce_store_api_cart_item_quantity_minimum', 1, $cart_item );
+
+		/**
+		* Filters the quantity maximum for a cart item in Store API.
+		*
+		* @param array $product Product being added/updated in the cart.
+		* @return number
+		*/
+		$maximum = (int) apply_filters( 'woocommerce_store_api_cart_item_quantity_maximum', is_null( $remaining_stock ) ? 99 : $remaining_stock, $cart_item );
+
+		/**
+		* Filters the quantity increment for a cart item in Store API.
+		*
+		* @param array $product Product being added/updated in the cart.
+		* @return number
+		*/
+		$multiple_of = (int) apply_filters( 'woocommerce_store_api_cart_item_quantity_multiple_of', 1, $cart_item );
+
+		return (object) [
+			'minimum'    => ceil( $minimum / $multiple_of ) * $multiple_of,
+			'maximum'    => floor( $maximum / $multiple_of ) * $multiple_of,
+			'multipleOf' => $multiple_of,
+		];
+	}
+
 	/**
 	 * Convert a WooCommerce cart item to an object suitable for the response.
 	 *
@@ -325,9 +388,7 @@ public function get_item_response( $cart_item ) {
 			'key'                  => $cart_item['key'],
 			'id'                   => $product->get_id(),
 			'quantity'             => wc_stock_amount( $cart_item['quantity'] ),
-			'quantity_limit'       => $this->get_product_quantity_limit( $product ),
-			'quantity_min'         => $this->get_item_quantity_min( $cart_item ),
-			'quantity_step'        => $this->get_item_quantity_step( $cart_item ),
+			'quantity_limits'      => $this->get_quantity_limits( $cart_item ),
 			'name'                 => $this->prepare_html_response( $product->get_title() ),
 			'short_description'    => $this->prepare_html_response( wc_format_content( wp_kses_post( $product->get_short_description() ) ) ),
 			'description'          => $this->prepare_html_response( wc_format_content( wp_kses_post( $product->get_description() ) ) ),
@@ -465,38 +526,6 @@ protected function get_item_data( $cart_item ) {
 		return array_map( [ $this, 'format_item_data_element' ], $item_data );
 	}
 
-	/**
-	 * Return the minimum quantity that's allowed for this item.
-	 *
-	 * @param array $cart_item Cart item array.
-	 * @return number
-	 */
-	protected function get_item_quantity_min( $cart_item ) {
-		/**
-		 * Filters the quantity minimum for a cart item in Store API.
-		 *
-		 * @param array $cart_item Cart item array.
-		 * @return number
-		 */
-		return apply_filters( 'woocommerce_store_api_item_quantity_minimum', 1, $cart_item );
-	}
-
-	/**
-	 * Return the increment quantity that an item is allowed to change with.
-	 *
-	 * @param array $cart_item Cart item array.
-	 * @return number
-	 */
-	protected function get_item_quantity_step( $cart_item ) {
-		/**
-		 * Filters the quantity increment for a cart item in Store API.
-		 *
-		 * @param array $cart_item Cart item array.
-		 * @return number
-		 */
-		return apply_filters( 'woocommerce_store_api_item_quantity_step', 1, $cart_item );
-	}
-
 	/**
 	 * Remove HTML tags from cart item data and set the `hidden` property to `__experimental_woocommerce_blocks_hidden`.
 	 *

From b58691e513ce0ea0c6a9fe5c3ca0cbb32e5c03a3 Mon Sep 17 00:00:00 2001
From: Mike Jolley <mike.jolley@me.com>
Date: Thu, 16 Dec 2021 14:44:45 +0000
Subject: [PATCH 09/17] Quantity validation

---
 .../components/quantity-selector/index.tsx    |   2 +-
 .../cart-line-item-row.tsx                    |   7 +-
 assets/js/types/type-defs/cart-response.ts    |  33 +-
 assets/js/types/type-defs/cart.ts             |   8 +-
 src/StoreApi/Routes/CartAddItem.php           |   2 +-
 src/StoreApi/Schemas/CartItemSchema.php       |  83 +---
 src/StoreApi/Utilities/CartController.php     |  41 +-
 src/StoreApi/Utilities/QuantityLimits.php     | 152 ++++++
 src/StoreApi/docs/cart-items.md               | 442 +++++++++---------
 src/StoreApi/docs/cart.md                     |  12 +-
 10 files changed, 432 insertions(+), 350 deletions(-)
 create mode 100644 src/StoreApi/Utilities/QuantityLimits.php

diff --git a/assets/js/base/components/quantity-selector/index.tsx b/assets/js/base/components/quantity-selector/index.tsx
index 94d3ca7a61b..b16ca2ccdc6 100644
--- a/assets/js/base/components/quantity-selector/index.tsx
+++ b/assets/js/base/components/quantity-selector/index.tsx
@@ -68,7 +68,7 @@ const QuantitySelector = ( {
 	);
 
 	const hasMaximum = typeof maximum !== 'undefined';
-	const canDecrease = quantity - step > minimum;
+	const canDecrease = quantity - step >= minimum;
 	const canIncrease = ! hasMaximum || quantity + step <= maximum;
 
 	/**
diff --git a/assets/js/blocks/cart-checkout/cart/cart-line-items-table/cart-line-item-row.tsx b/assets/js/blocks/cart-checkout/cart/cart-line-items-table/cart-line-item-row.tsx
index 8c1fa5445bc..0e7132445eb 100644
--- a/assets/js/blocks/cart-checkout/cart/cart-line-items-table/cart-line-item-row.tsx
+++ b/assets/js/blocks/cart-checkout/cart/cart-line-items-table/cart-line-item-row.tsx
@@ -73,8 +73,9 @@ const CartLineItemRow = forwardRef< HTMLTableRowElement, CartLineItemRowProps >(
 			quantity_limits: quantityLimits = {
 				minimum: 1,
 				maximum: 99,
-				multipleOf: 1,
+				multiple_of: 1,
 			},
+			sold_individually: soldIndividually = false,
 			permalink = '',
 			images = [],
 			variation = [],
@@ -282,13 +283,13 @@ const CartLineItemRow = forwardRef< HTMLTableRowElement, CartLineItemRowProps >(
 					/>
 
 					<div className="wc-block-cart-item__quantity">
-						{ !! quantityLimits && (
+						{ ! soldIndividually && (
 							<QuantitySelector
 								disabled={ isPendingDelete }
 								quantity={ quantity }
 								minimum={ quantityLimits.minimum }
 								maximum={ quantityLimits.maximum }
-								step={ quantityLimits.multipleOf }
+								step={ quantityLimits.multiple_of }
 								onChange={ ( newQuantity ) => {
 									setItemQuantity( newQuantity );
 									dispatchStoreEvent(
diff --git a/assets/js/types/type-defs/cart-response.ts b/assets/js/types/type-defs/cart-response.ts
index ee968c9dd86..925c093d990 100644
--- a/assets/js/types/type-defs/cart-response.ts
+++ b/assets/js/types/type-defs/cart-response.ts
@@ -2,13 +2,7 @@
  * Internal dependencies
  */
 import { CurrencyResponse } from './currency';
-import {
-	CartImageItem,
-	CartItemPrices,
-	CartItemTotals,
-	CartVariationItem,
-	CatalogVisibility,
-} from './cart';
+import { CartItem } from './cart';
 
 export interface CartResponseTotalsItem extends CurrencyResponse {
 	total_discount: string;
@@ -127,30 +121,7 @@ export interface CartResponseItemTotals extends CurrencyResponse {
 	line_total_tax: string;
 }
 
-export interface CartResponseItem {
-	key: string;
-	id: number;
-	quantity: number;
-	catalog_visibility: CatalogVisibility;
-	quantity_limit: number;
-	name: string;
-	summary: string;
-	short_description: string;
-	description: string;
-	sku: string;
-	low_stock_remaining: null | number;
-	backorders_allowed: boolean;
-	show_backorder_badge: boolean;
-	sold_individually: boolean;
-	permalink: string;
-	images: Array< CartImageItem >;
-	variation: Array< CartVariationItem >;
-	prices: CartItemPrices;
-	totals: CartItemTotals;
-	extensions: ExtensionsData;
-	item_data: Record< string, unknown >[];
-}
-
+export type CartResponseItem = CartItem;
 export interface CartResponseTotalsTaxLineItem {
 	name: string;
 	price: string;
diff --git a/assets/js/types/type-defs/cart.ts b/assets/js/types/type-defs/cart.ts
index 59b4c80c562..f7ed32c2c43 100644
--- a/assets/js/types/type-defs/cart.ts
+++ b/assets/js/types/type-defs/cart.ts
@@ -117,9 +117,11 @@ export interface CartItem {
 	id: number;
 	quantity: number;
 	catalog_visibility: CatalogVisibility;
-	quantity_limit: number;
-	quantity_min: number;
-	quantity_step: number;
+	quantity_limits: {
+		minimum: number;
+		maximum: number;
+		multiple_of: number;
+	};
 	name: string;
 	summary: string;
 	short_description: string;
diff --git a/src/StoreApi/Routes/CartAddItem.php b/src/StoreApi/Routes/CartAddItem.php
index 074c3f2d192..09aa901d733 100644
--- a/src/StoreApi/Routes/CartAddItem.php
+++ b/src/StoreApi/Routes/CartAddItem.php
@@ -35,7 +35,7 @@ public function get_args() {
 						'sanitize_callback' => 'absint',
 					],
 					'quantity'  => [
-						'description' => __( 'Quantity of this item in the cart.', 'woo-gutenberg-products-block' ),
+						'description' => __( 'Quantity of this item to add to the cart.', 'woo-gutenberg-products-block' ),
 						'type'        => 'integer',
 						'context'     => [ 'view', 'edit' ],
 						'arg_options' => [
diff --git a/src/StoreApi/Schemas/CartItemSchema.php b/src/StoreApi/Schemas/CartItemSchema.php
index 17213e59e04..b0f88248a11 100644
--- a/src/StoreApi/Schemas/CartItemSchema.php
+++ b/src/StoreApi/Schemas/CartItemSchema.php
@@ -2,7 +2,7 @@
 namespace Automattic\WooCommerce\Blocks\StoreApi\Schemas;
 
 use Automattic\WooCommerce\Blocks\StoreApi\Utilities\DraftOrderTrait;
-use Automattic\WooCommerce\Checkout\Helpers\ReserveStock;
+use Automattic\WooCommerce\Blocks\StoreApi\Utilities\QuantityLimits;
 /**
  * CartItemSchema class.
  *
@@ -52,24 +52,24 @@ public function get_properties() {
 				'readonly'    => true,
 			],
 			'quantity_limits'      => [
-				'description' => __( 'How the quantity of this item should be controlled, for example, any limits in place. This returns false if the input is disabled.', 'woo-gutenberg-products-block' ),
+				'description' => __( 'How the quantity of this item should be controlled, for example, any limits in place.', 'woo-gutenberg-products-block' ),
 				'type'        => [ 'object', 'boolean' ],
 				'context'     => [ 'view', 'edit' ],
 				'readonly'    => true,
 				'properties'  => [
-					'minimum'    => [
+					'minimum'     => [
 						'description' => __( 'The minimum quantity allowed in the cart for this line item.', 'woo-gutenberg-products-block' ),
 						'type'        => 'integer',
 						'context'     => [ 'view', 'edit' ],
 						'readonly'    => true,
 					],
-					'maximum'    => [
+					'maximum'     => [
 						'description' => __( 'The maximum quantity allowed in the cart for this line item.', 'woo-gutenberg-products-block' ),
 						'type'        => 'integer',
 						'context'     => [ 'view', 'edit' ],
 						'readonly'    => true,
 					],
-					'multipleOf' => [
+					'multiple_of' => [
 						'description' => __( 'The amount that quantities increment by. Quantity must be an increment of this value.', 'woo-gutenberg-products-block' ),
 						'type'        => 'integer',
 						'context'     => [ 'view', 'edit' ],
@@ -322,57 +322,17 @@ public function get_properties() {
 	}
 
 	/**
-	 * Return quantity limits e.g. min, max, and allowed multiples.
+	 * Return quantity limits e.g. min, max, and allowed multiples, for line items.
+	 *
+	 * These values will be enforced when adding and updating items in the cart.
 	 *
 	 * @param array $cart_item Cart item array.
-	 * @return object|boolean
+	 * @return object
 	 */
-	protected function get_quantity_limits( $cart_item ) {
-		$product = $cart_item['data'];
-
-		/**
-		* Filters the quantity input for a cart item in Store API.
-		*
-		* @param array $product Product being added/updated in the cart.
-		* @return number
-		*/
-		$disabled = apply_filters( 'woocommerce_store_api_cart_item_quantity_disabled', $product->is_sold_individually(), $cart_item );
-
-		if ( $disabled ) {
-			return false;
-		}
-
-		$remaining_stock = $this->get_remaining_stock( $product );
-
-		/**
-		* Filters the quantity minimum for a cart item in Store API.
-		*
-		* @param array $product Product being added/updated in the cart.
-		* @return number
-		*/
-		$minimum = (int) apply_filters( 'woocommerce_store_api_cart_item_quantity_minimum', 1, $cart_item );
-
-		/**
-		* Filters the quantity maximum for a cart item in Store API.
-		*
-		* @param array $product Product being added/updated in the cart.
-		* @return number
-		*/
-		$maximum = (int) apply_filters( 'woocommerce_store_api_cart_item_quantity_maximum', is_null( $remaining_stock ) ? 99 : $remaining_stock, $cart_item );
-
-		/**
-		* Filters the quantity increment for a cart item in Store API.
-		*
-		* @param array $product Product being added/updated in the cart.
-		* @return number
-		*/
-		$multiple_of = (int) apply_filters( 'woocommerce_store_api_cart_item_quantity_multiple_of', 1, $cart_item );
+	public function get_quantity_limits( $cart_item ) {
+		$quantity_limits = new QuantityLimits();
 
-		return (object) [
-			'minimum'    => ceil( $minimum / $multiple_of ) * $multiple_of,
-			'maximum'    => floor( $maximum / $multiple_of ) * $multiple_of,
-			'multipleOf' => $multiple_of,
-		];
+		return $quantity_limits->get_quantity_limits( $cart_item );
 	}
 
 	/**
@@ -438,25 +398,6 @@ protected function prepare_product_price_response( \WC_Product $product, $tax_di
 		return $prices;
 	}
 
-	/**
-	 * Returns the remaining stock for a product if it has stock.
-	 *
-	 * This also factors in draft orders.
-	 *
-	 * @param \WC_Product $product Product instance.
-	 * @return integer|null
-	 */
-	protected function get_remaining_stock( \WC_Product $product ) {
-		if ( is_null( $product->get_stock_quantity() ) ) {
-			return null;
-		}
-
-		$reserve_stock  = new ReserveStock();
-		$reserved_stock = $reserve_stock->get_reserved_stock( $product, $this->get_draft_order_id() );
-
-		return $product->get_stock_quantity() - $reserved_stock;
-	}
-
 	/**
 	 * Format variation data, for example convert slugs such as attribute_pa_size to Size.
 	 *
diff --git a/src/StoreApi/Utilities/CartController.php b/src/StoreApi/Utilities/CartController.php
index 5316d2c3fef..6224fc23c3c 100644
--- a/src/StoreApi/Utilities/CartController.php
+++ b/src/StoreApi/Utilities/CartController.php
@@ -4,6 +4,7 @@
 use Automattic\WooCommerce\Blocks\StoreApi\Routes\RouteException;
 use Automattic\WooCommerce\Blocks\StoreApi\Utilities\DraftOrderTrait;
 use Automattic\WooCommerce\Blocks\StoreApi\Utilities\NoticeHandler;
+use Automattic\WooCommerce\Blocks\StoreApi\Utilities\QuantityLimits;
 use Automattic\WooCommerce\Blocks\Utils\ArrayUtils;
 use Automattic\WooCommerce\Checkout\Helpers\ReserveStock;
 use WP_Error;
@@ -65,20 +66,22 @@ public function add_to_cart( $request ) {
 		$existing_cart_id = $cart->find_product_in_cart( $cart_id );
 
 		if ( $existing_cart_id ) {
-			if ( $product->is_sold_individually() ) {
-				throw new RouteException(
-					'woocommerce_rest_cart_product_sold_individually',
-					sprintf(
-						/* translators: %s: product name */
-						__( 'You cannot add another "%s" to your cart.', 'woo-gutenberg-products-block' ),
-						$product->get_name()
-					),
-					400
-				);
+			$cart_item           = $cart->cart_contents[ $existing_cart_id ];
+			$quantity_validation = ( new QuantityLimits() )->validate_quantity( $request['quantity'] + $cart_item['quantity'], $cart_item );
+
+			if ( is_wp_error( $quantity_validation ) ) {
+				throw new RouteException( $quantity_validation->get_error_code(), $quantity_validation->get_error_message(), 400 );
 			}
+
 			$cart->set_quantity( $existing_cart_id, $request['quantity'] + $cart->cart_contents[ $existing_cart_id ]['quantity'], true );
 
 			return $existing_cart_id;
+		} else {
+			$quantity_validation = ( new QuantityLimits() )->validate_quantity( $request['quantity'], $product );
+
+			if ( is_wp_error( $quantity_validation ) ) {
+				throw new RouteException( $quantity_validation->get_error_code(), $quantity_validation->get_error_message(), 400 );
+			}
 		}
 
 		/**
@@ -140,7 +143,8 @@ public function add_to_cart( $request ) {
 	}
 
 	/**
-	 * Based on core `set_quantity` method, but validates if an item is sold individually first.
+	 * Based on core `set_quantity` method, but validates if an item is sold individually first and enforces any limits in
+	 * place.
 	 *
 	 * @throws RouteException Exception if invalid data is detected.
 	 *
@@ -160,17 +164,12 @@ public function set_cart_item_quantity( $item_id, $quantity = 1 ) {
 			throw new RouteException( 'woocommerce_rest_cart_invalid_product', __( 'Cart item is invalid.', 'woo-gutenberg-products-block' ), 404 );
 		}
 
-		if ( $product->is_sold_individually() && $quantity > 1 ) {
-			throw new RouteException(
-				'woocommerce_rest_cart_product_sold_individually',
-				sprintf(
-					/* translators: %s: product name */
-					__( 'You cannot add another "%s" to your cart.', 'woo-gutenberg-products-block' ),
-					$product->get_name()
-				),
-				400
-			);
+		$quantity_validation = ( new QuantityLimits() )->validate_quantity( $quantity, $cart_item );
+
+		if ( is_wp_error( $quantity_validation ) ) {
+			throw new RouteException( $quantity_validation->get_error_code(), $quantity_validation->get_error_message(), 400 );
 		}
+
 		$cart = $this->get_cart_instance();
 		$cart->set_quantity( $item_id, $quantity );
 	}
diff --git a/src/StoreApi/Utilities/QuantityLimits.php b/src/StoreApi/Utilities/QuantityLimits.php
new file mode 100644
index 00000000000..294f4113d52
--- /dev/null
+++ b/src/StoreApi/Utilities/QuantityLimits.php
@@ -0,0 +1,152 @@
+<?php
+namespace Automattic\WooCommerce\Blocks\StoreApi\Utilities;
+
+use Automattic\WooCommerce\Checkout\Helpers\ReserveStock;
+use Automattic\WooCommerce\Blocks\StoreApi\Utilities\DraftOrderTrait;
+
+/**
+ * QuantityLimits class.
+ *
+ * Returns limits for products and cart items when using the StoreAPI and supporting classes.
+ *
+ * @internal This API is used internally by Blocks--it is still in flux and may be subject to revisions.
+ * @since 2.5.0
+ */
+class QuantityLimits {
+	use DraftOrderTrait;
+
+	/**
+	 * Check that a given quantity is valid according to any limits in place.
+	 *
+	 * @param integer           $quantity Quantity to validate.
+	 * @param \WC_Product|array $cart_item_or_product Either a cart item or a product instance.
+	 * @return \WP_Error|true
+	 */
+	public function validate_quantity( $quantity, $cart_item_or_product ) {
+		$limits = $this->get_quantity_limits( $cart_item_or_product );
+
+		if ( $quantity < $limits->minimum ) {
+			return new \WP_Error(
+				'invalid_quantity',
+				sprintf(
+					// Translators: %s amount.
+					__( 'The minimum quantity that can be added to the cart is %s', 'woo-gutenberg-products-block' ),
+					$limits->minimum
+				)
+			);
+		}
+
+		if ( $quantity > $limits->maximum ) {
+			return new \WP_Error(
+				'invalid_quantity',
+				sprintf(
+					// Translators: %s amount.
+					__( 'The maximum quantity that can be added to the cart is %s', 'woo-gutenberg-products-block' ),
+					$limits->maximum
+				)
+			);
+		}
+
+		if ( $quantity % $limits->multiple_of ) {
+			return new \WP_Error(
+				'invalid_quantity',
+				sprintf(
+					// Translators: %s amount.
+					__( 'The quantity added to the cart must be a multiple of %s', 'woo-gutenberg-products-block' ),
+					$limits->multiple_of
+				)
+			);
+		}
+
+		return true;
+	}
+
+	/**
+	 * Get quantity limits (min, max, step/multiple) for a product or cart item.
+	 *
+	 * @param \WC_Product|array $cart_item_or_product Either a cart item or a product instance.
+	 * @return object
+	 */
+	public function get_quantity_limits( $cart_item_or_product ) {
+		$product = $cart_item_or_product instanceof \WC_Product ? $cart_item_or_product : $cart_item_or_product['data'];
+
+		if ( ! $product instanceof \WC_Product ) {
+			return [
+				'minimum'     => 1,
+				'maximum'     => null,
+				'multiple_of' => 1,
+			];
+		}
+
+		$product_limit = $product->is_sold_individually() ? 1 : $this->get_remaining_stock( $product );
+		$multiple_of   = $this->filter_value( 1, 'multiple_of', $cart_item_or_product );
+		$minimum       = $this->filter_value( 1, 'minimum', $cart_item_or_product );
+		$maximum       = $this->filter_value( $product_limit ? $product_limit : $this->limit_to_multiple( 99, $multiple_of, 'ceil' ), 'maximum', $cart_item_or_product );
+
+		return (object) [
+			'minimum'     => $this->limit_to_multiple( $minimum, $multiple_of, 'ceil' ),
+			'maximum'     => $this->limit_to_multiple( $maximum, $multiple_of, 'floor' ),
+			'multiple_of' => $multiple_of,
+		];
+	}
+
+	/**
+	 * Returns the remaining stock for a product if it has stock.
+	 *
+	 * This also factors in draft orders.
+	 *
+	 * @param \WC_Product $product Product instance.
+	 * @return integer|null
+	 */
+	protected function get_remaining_stock( \WC_Product $product ) {
+		if ( is_null( $product->get_stock_quantity() ) ) {
+			return null;
+		}
+
+		$reserve_stock  = new ReserveStock();
+		$reserved_stock = $reserve_stock->get_reserved_stock( $product, $this->get_draft_order_id() );
+
+		return $product->get_stock_quantity() - $reserved_stock;
+	}
+
+	/**
+	 * Get a quantity for a product or cart item by running it through a filter hook.
+	 *
+	 * @param int|null          $value Value to filter.
+	 * @param string            $value_type Type of value. Used for filter suffix.
+	 * @param \WC_Product|array $cart_item_or_product Either a cart item or a product instance.
+	 * @return int|null
+	 */
+	protected function filter_value( $value, string $value_type, $cart_item_or_product ) {
+		$type = $cart_item_or_product instanceof \WC_Product ? 'product' : 'cart_item';
+		/**
+		 * Filters the quantity minimum for a cart item in Store API. This allows extensions to control the minimum qty
+		 * of items already within the cart.
+		 *
+		 * Hook name will reflect the product or cart item depending on what is provided, so either:
+		 *  - woocommerce_store_api_product_quantity_minimum
+		 *  - woocommerce_store_api_cart_item_quantity_minimum
+		 *
+		 * @param integer $minimum Minimum qty which defaults to 1.
+		 * @param array $cart_item_or_product Product or cart item being added/updated in the cart.
+		 * @return integer
+		 */
+		return (int) apply_filters( "woocommerce_store_api_{$type}_quantity_{$value_type}", $value, $cart_item_or_product );
+	}
+
+	/**
+	 * Return a number using the closest multiple of another number. Used to enforce step/multiple values.
+	 *
+	 * @param int    $number Number to round.
+	 * @param int    $multiple_of The multiple.
+	 * @param string $rounding_function ceil, floor, or round.
+	 * @return int
+	 */
+	protected function limit_to_multiple( int $number, int $multiple_of, string $rounding_function = 'ceil' ) {
+		if ( $multiple_of <= 1 ) {
+			return $number;
+		}
+		$rounding_function = in_array( $rounding_function, [ 'ceil', 'floor', 'round' ], true ) ? $rounding_function : 'round';
+		return $rounding_function( $number / $multiple_of ) * $multiple_of;
+	}
+}
diff --git a/src/StoreApi/docs/cart-items.md b/src/StoreApi/docs/cart-items.md
index 01f17a83c1a..272238b2da8 100644
--- a/src/StoreApi/docs/cart-items.md
+++ b/src/StoreApi/docs/cart-items.md
@@ -23,152 +23,160 @@ curl "https://example-store.com/wp-json/wc/store/cart/items"
 
 ```json
 [
-  {
-    "key": "9bf31c7ff062936a96d3c8bd1f8f2ff3",
-    "id": 15,
-    "quantity": 1,
-    "quantity_limit": 99,
-    "name": "Beanie",
-    "summary": "<p>This is a simple product.<\/p>",
-    "short_description": "<p>This is a simple product.<\/p>",
-    "description": "<p>Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Vestibulum tortor quam, feugiat vitae, ultricies eget, tempor sit amet, ante. Donec eu libero sit amet quam egestas semper. Aenean ultricies mi vitae est. Mauris placerat eleifend leo.<\/p>",
-    "sku": "woo-beanie",
-    "low_stock_remaining": null,
-    "backorders_allowed": false,
-    "show_backorder_badge": false,
-    "sold_individually": false,
-    "permalink": "https:\/\/local.wordpress.test\/product\/beanie\/",
-    "images": [
-      {
-        "id": 44,
-        "src": "https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/beanie-2.jpg",
-        "thumbnail": "https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/beanie-2-324x324.jpg",
-        "srcset": "https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/beanie-2.jpg 801w, https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/beanie-2-324x324.jpg 324w, https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/beanie-2-100x100.jpg 100w, https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/beanie-2-416x416.jpg 416w, https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/beanie-2-300x300.jpg 300w, https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/beanie-2-150x150.jpg 150w, https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/beanie-2-768x768.jpg 768w",
-        "sizes": "(max-width: 801px) 100vw, 801px",
-        "name": "beanie-2.jpg",
-        "alt": ""
-      }
-    ],
-    "variation": [],
-    "item_data": [],
-    "prices": {
-      "currency_code": "GBP",
-      "currency_symbol": "£",
-      "currency_minor_unit": 2,
-      "currency_decimal_separator": ".",
-      "currency_thousand_separator": ",",
-      "currency_prefix": "£",
-      "currency_suffix": "",
-      "price": "1000",
-      "regular_price": "2000",
-      "sale_price": "1000",
-      "price_range": null,
-      "raw_prices": {
-        "precision": 6,
-        "price": "10000000",
-        "regular_price": "20000000",
-        "sale_price": "10000000"
-      }
-    },
-    "totals": {
-      "currency_code": "GBP",
-      "currency_symbol": "£",
-      "currency_minor_unit": 2,
-      "currency_decimal_separator": ".",
-      "currency_thousand_separator": ",",
-      "currency_prefix": "£",
-      "currency_suffix": "",
-      "line_subtotal": "1000",
-      "line_subtotal_tax": "0",
-      "line_total": "800",
-      "line_total_tax": "0"
-    },
-    "_links": {
-      "self": [
-        {
-          "href": "https:\/\/local.wordpress.test\/wp-json\/wc\/store\/cart\/items\/9bf31c7ff062936a96d3c8bd1f8f2ff3"
-        }
-      ],
-      "collection": [
-        {
-          "href": "https:\/\/local.wordpress.test\/wp-json\/wc\/store\/cart\/items"
-        }
-      ]
-    }
-  },
-  {
-    "key": "e369853df766fa44e1ed0ff613f563bd",
-    "id": 34,
-    "quantity": 1,
-    "quantity_limit": 99,
-    "name": "WordPress Pennant",
-    "summary": "<p>This is an external product.<\/p>",
-    "short_description": "<p>This is an external product.<\/p>",
-    "description": "<p>Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Vestibulum tortor quam, feugiat vitae, ultricies eget, tempor sit amet, ante. Donec eu libero sit amet quam egestas semper. Aenean ultricies mi vitae est. Mauris placerat eleifend leo.<\/p>",
-    "sku": "wp-pennant",
-    "low_stock_remaining": null,
-    "backorders_allowed": false,
-    "show_backorder_badge": false,
-    "sold_individually": false,
-    "permalink": "https:\/\/local.wordpress.test\/product\/wordpress-pennant\/",
-    "images": [
-      {
-        "id": 57,
-        "src": "https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/pennant-1.jpg",
-        "thumbnail": "https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/pennant-1-324x324.jpg",
-        "srcset": "https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/pennant-1.jpg 800w, https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/pennant-1-324x324.jpg 324w, https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/pennant-1-100x100.jpg 100w, https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/pennant-1-416x416.jpg 416w, https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/pennant-1-300x300.jpg 300w, https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/pennant-1-150x150.jpg 150w, https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/pennant-1-768x768.jpg 768w",
-        "sizes": "(max-width: 800px) 100vw, 800px",
-        "name": "pennant-1.jpg",
-        "alt": ""
-      }
-    ],
-    "variation": [],
-    "item_data": [],
-    "prices": {
-      "currency_code": "GBP",
-      "currency_symbol": "£",
-      "currency_minor_unit": 2,
-      "currency_decimal_separator": ".",
-      "currency_thousand_separator": ",",
-      "currency_prefix": "£",
-      "currency_suffix": "",
-      "price": "1105",
-      "regular_price": "1105",
-      "sale_price": "1105",
-      "price_range": null,
-      "raw_prices": {
-        "precision": 6,
-        "price": "11050000",
-        "regular_price": "11050000",
-        "sale_price": "11050000"
-      }
-    },
-    "totals": {
-      "currency_code": "GBP",
-      "currency_symbol": "£",
-      "currency_minor_unit": 2,
-      "currency_decimal_separator": ".",
-      "currency_thousand_separator": ",",
-      "currency_prefix": "£",
-      "currency_suffix": "",
-      "line_subtotal": "1105",
-      "line_subtotal_tax": "0",
-      "line_total": "884",
-      "line_total_tax": "0"
-    },
-    "_links": {
-      "self": [
-        {
-          "href": "https:\/\/local.wordpress.test\/wp-json\/wc\/store\/cart\/items\/e369853df766fa44e1ed0ff613f563bd"
-        }
-      ],
-      "collection": [
-        {
-          "href": "https:\/\/local.wordpress.test\/wp-json\/wc\/store\/cart\/items"
-        }
-      ]
-    }
-  }
+	{
+		"key": "9bf31c7ff062936a96d3c8bd1f8f2ff3",
+		"id": 15,
+		"quantity": 1,
+		"quantity_limits": {
+			"minimum": 1,
+			"maximum": 99,
+			"multiple_of": 1
+		},
+		"name": "Beanie",
+		"summary": "<p>This is a simple product.</p>",
+		"short_description": "<p>This is a simple product.</p>",
+		"description": "<p>Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Vestibulum tortor quam, feugiat vitae, ultricies eget, tempor sit amet, ante. Donec eu libero sit amet quam egestas semper. Aenean ultricies mi vitae est. Mauris placerat eleifend leo.</p>",
+		"sku": "woo-beanie",
+		"low_stock_remaining": null,
+		"backorders_allowed": false,
+		"show_backorder_badge": false,
+		"sold_individually": false,
+		"permalink": "https://local.wordpress.test/product/beanie/",
+		"images": [
+			{
+				"id": 44,
+				"src": "https://local.wordpress.test/wp-content/uploads/2020/03/beanie-2.jpg",
+				"thumbnail": "https://local.wordpress.test/wp-content/uploads/2020/03/beanie-2-324x324.jpg",
+				"srcset": "https://local.wordpress.test/wp-content/uploads/2020/03/beanie-2.jpg 801w, https://local.wordpress.test/wp-content/uploads/2020/03/beanie-2-324x324.jpg 324w, https://local.wordpress.test/wp-content/uploads/2020/03/beanie-2-100x100.jpg 100w, https://local.wordpress.test/wp-content/uploads/2020/03/beanie-2-416x416.jpg 416w, https://local.wordpress.test/wp-content/uploads/2020/03/beanie-2-300x300.jpg 300w, https://local.wordpress.test/wp-content/uploads/2020/03/beanie-2-150x150.jpg 150w, https://local.wordpress.test/wp-content/uploads/2020/03/beanie-2-768x768.jpg 768w",
+				"sizes": "(max-width: 801px) 100vw, 801px",
+				"name": "beanie-2.jpg",
+				"alt": ""
+			}
+		],
+		"variation": [],
+		"item_data": [],
+		"prices": {
+			"currency_code": "GBP",
+			"currency_symbol": "£",
+			"currency_minor_unit": 2,
+			"currency_decimal_separator": ".",
+			"currency_thousand_separator": ",",
+			"currency_prefix": "£",
+			"currency_suffix": "",
+			"price": "1000",
+			"regular_price": "2000",
+			"sale_price": "1000",
+			"price_range": null,
+			"raw_prices": {
+				"precision": 6,
+				"price": "10000000",
+				"regular_price": "20000000",
+				"sale_price": "10000000"
+			}
+		},
+		"totals": {
+			"currency_code": "GBP",
+			"currency_symbol": "£",
+			"currency_minor_unit": 2,
+			"currency_decimal_separator": ".",
+			"currency_thousand_separator": ",",
+			"currency_prefix": "£",
+			"currency_suffix": "",
+			"line_subtotal": "1000",
+			"line_subtotal_tax": "0",
+			"line_total": "800",
+			"line_total_tax": "0"
+		},
+		"_links": {
+			"self": [
+				{
+					"href": "https://local.wordpress.test/wp-json/wc/store/cart/items/9bf31c7ff062936a96d3c8bd1f8f2ff3"
+				}
+			],
+			"collection": [
+				{
+					"href": "https://local.wordpress.test/wp-json/wc/store/cart/items"
+				}
+			]
+		}
+	},
+	{
+		"key": "e369853df766fa44e1ed0ff613f563bd",
+		"id": 34,
+		"quantity": 1,
+		"quantity_limits": {
+			"minimum": 1,
+			"maximum": 99,
+			"multiple_of": 1
+		},
+		"name": "WordPress Pennant",
+		"summary": "<p>This is an external product.</p>",
+		"short_description": "<p>This is an external product.</p>",
+		"description": "<p>Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Vestibulum tortor quam, feugiat vitae, ultricies eget, tempor sit amet, ante. Donec eu libero sit amet quam egestas semper. Aenean ultricies mi vitae est. Mauris placerat eleifend leo.</p>",
+		"sku": "wp-pennant",
+		"low_stock_remaining": null,
+		"backorders_allowed": false,
+		"show_backorder_badge": false,
+		"sold_individually": false,
+		"permalink": "https://local.wordpress.test/product/wordpress-pennant/",
+		"images": [
+			{
+				"id": 57,
+				"src": "https://local.wordpress.test/wp-content/uploads/2020/03/pennant-1.jpg",
+				"thumbnail": "https://local.wordpress.test/wp-content/uploads/2020/03/pennant-1-324x324.jpg",
+				"srcset": "https://local.wordpress.test/wp-content/uploads/2020/03/pennant-1.jpg 800w, https://local.wordpress.test/wp-content/uploads/2020/03/pennant-1-324x324.jpg 324w, https://local.wordpress.test/wp-content/uploads/2020/03/pennant-1-100x100.jpg 100w, https://local.wordpress.test/wp-content/uploads/2020/03/pennant-1-416x416.jpg 416w, https://local.wordpress.test/wp-content/uploads/2020/03/pennant-1-300x300.jpg 300w, https://local.wordpress.test/wp-content/uploads/2020/03/pennant-1-150x150.jpg 150w, https://local.wordpress.test/wp-content/uploads/2020/03/pennant-1-768x768.jpg 768w",
+				"sizes": "(max-width: 800px) 100vw, 800px",
+				"name": "pennant-1.jpg",
+				"alt": ""
+			}
+		],
+		"variation": [],
+		"item_data": [],
+		"prices": {
+			"currency_code": "GBP",
+			"currency_symbol": "£",
+			"currency_minor_unit": 2,
+			"currency_decimal_separator": ".",
+			"currency_thousand_separator": ",",
+			"currency_prefix": "£",
+			"currency_suffix": "",
+			"price": "1105",
+			"regular_price": "1105",
+			"sale_price": "1105",
+			"price_range": null,
+			"raw_prices": {
+				"precision": 6,
+				"price": "11050000",
+				"regular_price": "11050000",
+				"sale_price": "11050000"
+			}
+		},
+		"totals": {
+			"currency_code": "GBP",
+			"currency_symbol": "£",
+			"currency_minor_unit": 2,
+			"currency_decimal_separator": ".",
+			"currency_thousand_separator": ",",
+			"currency_prefix": "£",
+			"currency_suffix": "",
+			"line_subtotal": "1105",
+			"line_subtotal_tax": "0",
+			"line_total": "884",
+			"line_total_tax": "0"
+		},
+		"_links": {
+			"self": [
+				{
+					"href": "https://local.wordpress.test/wp-json/wc/store/cart/items/e369853df766fa44e1ed0ff613f563bd"
+				}
+			],
+			"collection": [
+				{
+					"href": "https://local.wordpress.test/wp-json/wc/store/cart/items"
+				}
+			]
+		}
+	}
 ]
 ```
 
@@ -192,77 +200,77 @@ curl "https://example-store.com/wp-json/wc/store/cart/items/e369853df766fa44e1ed
 
 ```json
 {
-  "key": "e369853df766fa44e1ed0ff613f563bd",
-  "id": 34,
-  "quantity": 1,
-  "quantity_limit": 99,
-  "name": "WordPress Pennant",
-  "summary": "<p>This is an external product.<\/p>",
-  "short_description": "<p>This is an external product.<\/p>",
-  "description": "<p>Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Vestibulum tortor quam, feugiat vitae, ultricies eget, tempor sit amet, ante. Donec eu libero sit amet quam egestas semper. Aenean ultricies mi vitae est. Mauris placerat eleifend leo.<\/p>",
-  "sku": "wp-pennant",
-  "low_stock_remaining": null,
-  "backorders_allowed": false,
-  "show_backorder_badge": false,
-  "sold_individually": false,
-  "permalink": "https:\/\/local.wordpress.test\/product\/wordpress-pennant\/",
-  "images": [
-    {
-      "id": 57,
-      "src": "https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/pennant-1.jpg",
-      "thumbnail": "https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/pennant-1-324x324.jpg",
-      "srcset": "https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/pennant-1.jpg 800w, https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/pennant-1-324x324.jpg 324w, https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/pennant-1-100x100.jpg 100w, https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/pennant-1-416x416.jpg 416w, https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/pennant-1-300x300.jpg 300w, https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/pennant-1-150x150.jpg 150w, https:\/\/local.wordpress.test\/wp-content\/uploads\/2020\/03\/pennant-1-768x768.jpg 768w",
-      "sizes": "(max-width: 800px) 100vw, 800px",
-      "name": "pennant-1.jpg",
-      "alt": ""
-    }
-  ],
-  "variation": [],
-  "item_data": [],
-  "prices": {
-    "currency_code": "GBP",
-    "currency_symbol": "£",
-    "currency_minor_unit": 2,
-    "currency_decimal_separator": ".",
-    "currency_thousand_separator": ",",
-    "currency_prefix": "£",
-    "currency_suffix": "",
-    "price": "1105",
-    "regular_price": "1105",
-    "sale_price": "1105",
-    "price_range": null,
-    "raw_prices": {
-      "precision": 6,
-      "price": "11050000",
-      "regular_price": "11050000",
-      "sale_price": "11050000"
-    }
-  },
-  "totals": {
-    "currency_code": "GBP",
-    "currency_symbol": "£",
-    "currency_minor_unit": 2,
-    "currency_decimal_separator": ".",
-    "currency_thousand_separator": ",",
-    "currency_prefix": "£",
-    "currency_suffix": "",
-    "line_subtotal": "1105",
-    "line_subtotal_tax": "0",
-    "line_total": "884",
-    "line_total_tax": "0"
-  },
-  "_links": {
-    "self": [
-      {
-        "href": "https:\/\/local.wordpress.test\/wp-json\/wc\/store\/cart\/items\/(?P<key>[\\w-]{32})\/e369853df766fa44e1ed0ff613f563bd"
-      }
-    ],
-    "collection": [
-      {
-        "href": "https:\/\/local.wordpress.test\/wp-json\/wc\/store\/cart\/items\/(?P<key>[\\w-]{32})"
-      }
-    ]
-  }
+	"key": "e369853df766fa44e1ed0ff613f563bd",
+	"id": 34,
+	"quantity": 1,
+	"quantity_limit": 99,
+	"name": "WordPress Pennant",
+	"summary": "<p>This is an external product.</p>",
+	"short_description": "<p>This is an external product.</p>",
+	"description": "<p>Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Vestibulum tortor quam, feugiat vitae, ultricies eget, tempor sit amet, ante. Donec eu libero sit amet quam egestas semper. Aenean ultricies mi vitae est. Mauris placerat eleifend leo.</p>",
+	"sku": "wp-pennant",
+	"low_stock_remaining": null,
+	"backorders_allowed": false,
+	"show_backorder_badge": false,
+	"sold_individually": false,
+	"permalink": "https://local.wordpress.test/product/wordpress-pennant/",
+	"images": [
+		{
+			"id": 57,
+			"src": "https://local.wordpress.test/wp-content/uploads/2020/03/pennant-1.jpg",
+			"thumbnail": "https://local.wordpress.test/wp-content/uploads/2020/03/pennant-1-324x324.jpg",
+			"srcset": "https://local.wordpress.test/wp-content/uploads/2020/03/pennant-1.jpg 800w, https://local.wordpress.test/wp-content/uploads/2020/03/pennant-1-324x324.jpg 324w, https://local.wordpress.test/wp-content/uploads/2020/03/pennant-1-100x100.jpg 100w, https://local.wordpress.test/wp-content/uploads/2020/03/pennant-1-416x416.jpg 416w, https://local.wordpress.test/wp-content/uploads/2020/03/pennant-1-300x300.jpg 300w, https://local.wordpress.test/wp-content/uploads/2020/03/pennant-1-150x150.jpg 150w, https://local.wordpress.test/wp-content/uploads/2020/03/pennant-1-768x768.jpg 768w",
+			"sizes": "(max-width: 800px) 100vw, 800px",
+			"name": "pennant-1.jpg",
+			"alt": ""
+		}
+	],
+	"variation": [],
+	"item_data": [],
+	"prices": {
+		"currency_code": "GBP",
+		"currency_symbol": "£",
+		"currency_minor_unit": 2,
+		"currency_decimal_separator": ".",
+		"currency_thousand_separator": ",",
+		"currency_prefix": "£",
+		"currency_suffix": "",
+		"price": "1105",
+		"regular_price": "1105",
+		"sale_price": "1105",
+		"price_range": null,
+		"raw_prices": {
+			"precision": 6,
+			"price": "11050000",
+			"regular_price": "11050000",
+			"sale_price": "11050000"
+		}
+	},
+	"totals": {
+		"currency_code": "GBP",
+		"currency_symbol": "£",
+		"currency_minor_unit": 2,
+		"currency_decimal_separator": ".",
+		"currency_thousand_separator": ",",
+		"currency_prefix": "£",
+		"currency_suffix": "",
+		"line_subtotal": "1105",
+		"line_subtotal_tax": "0",
+		"line_total": "884",
+		"line_total_tax": "0"
+	},
+	"_links": {
+		"self": [
+			{
+				"href": "https://local.wordpress.test/wp-json/wc/store/cart/items/(?P<key>[\\w-]{32})/e369853df766fa44e1ed0ff613f563bd"
+			}
+		],
+		"collection": [
+			{
+				"href": "https://local.wordpress.test/wp-json/wc/store/cart/items/(?P<key>[\\w-]{32})"
+			}
+		]
+	}
 }
 ```
 
diff --git a/src/StoreApi/docs/cart.md b/src/StoreApi/docs/cart.md
index 4cd6c0885a9..9e27a28c2f5 100644
--- a/src/StoreApi/docs/cart.md
+++ b/src/StoreApi/docs/cart.md
@@ -107,7 +107,11 @@ All endpoints under `/cart` (listed in this doc) return responses in the same fo
 			"key": "9bf31c7ff062936a96d3c8bd1f8f2ff3",
 			"id": 15,
 			"quantity": 1,
-			"quantity_limit": 99,
+			"quantity_limits": {
+				"minimum": 1,
+				"maximum": 99,
+				"multiple_of": 1
+			},
 			"name": "Beanie",
 			"summary": "<p>This is a simple product.</p>",
 			"short_description": "<p>This is a simple product.</p>",
@@ -167,7 +171,11 @@ All endpoints under `/cart` (listed in this doc) return responses in the same fo
 			"key": "e369853df766fa44e1ed0ff613f563bd",
 			"id": 34,
 			"quantity": 1,
-			"quantity_limit": 99,
+			"quantity_limits": {
+				"minimum": 1,
+				"maximum": 99,
+				"multiple_of": 1
+			},
 			"name": "WordPress Pennant",
 			"summary": "<p>This is an external product.</p>",
 			"short_description": "<p>This is an external product.</p>",

From 04606c99dcfee44e5417373e6c0313bf669ba3a0 Mon Sep 17 00:00:00 2001
From: Mike Jolley <mike.jolley@me.com>
Date: Thu, 16 Dec 2021 17:30:44 +0000
Subject: [PATCH 10/17] Update product API

---
 .../add-to-cart-form/form-state/index.js      |   2 +-
 .../js/shared/context/product-data-context.js |   6 +-
 assets/js/types/type-defs/product-response.ts |   6 +-
 src/StoreApi/Schemas/CartItemSchema.php       |  16 +--
 src/StoreApi/Schemas/ProductSchema.php        |  58 ++++----
 src/StoreApi/Utilities/QuantityLimits.php     | 125 +++++++++++-------
 src/StoreApi/docs/cart-items.md               |   6 +-
 7 files changed, 120 insertions(+), 99 deletions(-)

diff --git a/assets/js/base/context/providers/add-to-cart-form/form-state/index.js b/assets/js/base/context/providers/add-to-cart-form/form-state/index.js
index 4a409eb5f9b..35508304322 100644
--- a/assets/js/base/context/providers/add-to-cart-form/form-state/index.js
+++ b/assets/js/base/context/providers/add-to-cart-form/form-state/index.js
@@ -298,7 +298,7 @@ export const AddToCartFormStateContextProvider = ( {
 		showFormElements: showFormElements && supportsFormElements,
 		quantity: addToCartFormState.quantity,
 		minQuantity: 1,
-		maxQuantity: product.quantity_limit || 99,
+		maxQuantity: product?.quantity_limits?.maximum || 99,
 		requestParams: addToCartFormState.requestParams,
 		isIdle: addToCartFormState.status === STATUS.IDLE,
 		isDisabled: addToCartFormState.status === STATUS.DISABLED,
diff --git a/assets/js/shared/context/product-data-context.js b/assets/js/shared/context/product-data-context.js
index 1726d497f6e..c0fc1bd60f9 100644
--- a/assets/js/shared/context/product-data-context.js
+++ b/assets/js/shared/context/product-data-context.js
@@ -45,7 +45,11 @@ const defaultProductData = {
 	is_on_backorder: false,
 	low_stock_remaining: null,
 	sold_individually: false,
-	quantity_limit: 99,
+	quantity_limits: {
+		minimum: 1,
+		maximum: 99,
+		multiple_of: 1,
+	},
 	add_to_cart: {
 		text: 'Add to cart',
 		description: 'Add to cart',
diff --git a/assets/js/types/type-defs/product-response.ts b/assets/js/types/type-defs/product-response.ts
index 56baaaa1d54..cac37d6473a 100644
--- a/assets/js/types/type-defs/product-response.ts
+++ b/assets/js/types/type-defs/product-response.ts
@@ -86,7 +86,11 @@ export interface ProductResponseItem {
 	is_on_backorder: boolean;
 	low_stock_remaining: null | number;
 	sold_individually: boolean;
-	quantity_limit: number;
+	quantity_limits: {
+		minimum: number;
+		maximum: number;
+		multiple_of: number;
+	};
 	add_to_cart: {
 		text: string;
 		description: string;
diff --git a/src/StoreApi/Schemas/CartItemSchema.php b/src/StoreApi/Schemas/CartItemSchema.php
index b0f88248a11..746d0178966 100644
--- a/src/StoreApi/Schemas/CartItemSchema.php
+++ b/src/StoreApi/Schemas/CartItemSchema.php
@@ -321,20 +321,6 @@ public function get_properties() {
 		];
 	}
 
-	/**
-	 * Return quantity limits e.g. min, max, and allowed multiples, for line items.
-	 *
-	 * These values will be enforced when adding and updating items in the cart.
-	 *
-	 * @param array $cart_item Cart item array.
-	 * @return object
-	 */
-	public function get_quantity_limits( $cart_item ) {
-		$quantity_limits = new QuantityLimits();
-
-		return $quantity_limits->get_quantity_limits( $cart_item );
-	}
-
 	/**
 	 * Convert a WooCommerce cart item to an object suitable for the response.
 	 *
@@ -348,7 +334,7 @@ public function get_item_response( $cart_item ) {
 			'key'                  => $cart_item['key'],
 			'id'                   => $product->get_id(),
 			'quantity'             => wc_stock_amount( $cart_item['quantity'] ),
-			'quantity_limits'      => $this->get_quantity_limits( $cart_item ),
+			'quantity_limits'      => ( new QuantityLimits() )->get_quantity_limits( $cart_item ),
 			'name'                 => $this->prepare_html_response( $product->get_title() ),
 			'short_description'    => $this->prepare_html_response( wc_format_content( wp_kses_post( $product->get_short_description() ) ) ),
 			'description'          => $this->prepare_html_response( wc_format_content( wp_kses_post( $product->get_description() ) ) ),
diff --git a/src/StoreApi/Schemas/ProductSchema.php b/src/StoreApi/Schemas/ProductSchema.php
index 278e6f666ba..a1f86f0103f 100644
--- a/src/StoreApi/Schemas/ProductSchema.php
+++ b/src/StoreApi/Schemas/ProductSchema.php
@@ -2,7 +2,7 @@
 namespace Automattic\WooCommerce\Blocks\StoreApi\Schemas;
 
 use Automattic\WooCommerce\Blocks\Domain\Services\ExtendRestApi;
-
+use Automattic\WooCommerce\Blocks\StoreApi\Utilities\QuantityLimits;
 
 /**
  * ProductSchema class.
@@ -392,11 +392,32 @@ public function get_properties() {
 				'context'     => [ 'view', 'edit' ],
 				'readonly'    => true,
 			],
-			'quantity_limit'      => [
-				'description' => __( 'The maximum quantity than can be added to the cart at once.', 'woo-gutenberg-products-block' ),
-				'type'        => 'integer',
+			'quantity_limits'     => [
+				'description' => __( 'How the quantity of this item should be controlled, for example, any limits in place.', 'woo-gutenberg-products-block' ),
+				'type'        => [ 'object', 'boolean' ],
 				'context'     => [ 'view', 'edit' ],
 				'readonly'    => true,
+				'properties'  => [
+					'minimum'     => [
+						'description' => __( 'The minimum quantity allowed in the cart for this line item.', 'woo-gutenberg-products-block' ),
+						'type'        => 'integer',
+						'context'     => [ 'view', 'edit' ],
+						'readonly'    => true,
+					],
+					'maximum'     => [
+						'description' => __( 'The maximum quantity allowed in the cart for this line item.', 'woo-gutenberg-products-block' ),
+						'type'        => 'integer',
+						'context'     => [ 'view', 'edit' ],
+						'readonly'    => true,
+					],
+					'multiple_of' => [
+						'description' => __( 'The amount that quantities increment by. Quantity must be an increment of this value.', 'woo-gutenberg-products-block' ),
+						'type'        => 'integer',
+						'context'     => [ 'view', 'edit' ],
+						'readonly'    => true,
+						'default'     => 1,
+					],
+				],
 			],
 			'add_to_cart'         => [
 				'description' => __( 'Add to cart button parameters.', 'woo-gutenberg-products-block' ),
@@ -460,7 +481,7 @@ public function get_item_response( $product ) {
 			'is_on_backorder'     => 'onbackorder' === $product->get_stock_status(),
 			'low_stock_remaining' => $this->get_low_stock_remaining( $product ),
 			'sold_individually'   => $product->is_sold_individually(),
-			'quantity_limit'      => $this->get_product_quantity_limit( $product ),
+			'quantity_limits'     => ( new QuantityLimits() )->get_quantity_limits( $product ),
 			'add_to_cart'         => (object) $this->prepare_html_response(
 				[
 					'text'        => $product->add_to_cart_text(),
@@ -512,33 +533,6 @@ protected function get_low_stock_remaining( \WC_Product $product ) {
 		return null;
 	}
 
-	/**
-	 * Get the quantity limit for an item in the cart.
-	 *
-	 * @param \WC_Product $product Product instance.
-	 * @return int
-	 */
-	protected function get_product_quantity_limit( \WC_Product $product ) {
-		$limits = [ 99 ];
-
-		if ( $product->is_sold_individually() ) {
-			$limits[] = 1;
-		} elseif ( ! $product->backorders_allowed() ) {
-			$limits[] = $this->get_remaining_stock( $product );
-		}
-
-		/**
-		 * Filters the quantity limit for a product being added to the cart via the Store API.
-		 *
-		 * Filters the variation option name for custom option slugs.
-		 *
-		 * @param integer $quantity_limit Quantity limit which defaults to 99 unless sold individually.
-		 * @param \WC_Product $product Product instance.
-		 * @return integer
-		 */
-		return apply_filters( 'woocommerce_store_api_product_quantity_limit', max( min( array_filter( $limits ) ), 1 ), $product );
-	}
-
 	/**
 	 * Returns true if the given attribute is valid.
 	 *
diff --git a/src/StoreApi/Utilities/QuantityLimits.php b/src/StoreApi/Utilities/QuantityLimits.php
index 294f4113d52..3cf2e8545ea 100644
--- a/src/StoreApi/Utilities/QuantityLimits.php
+++ b/src/StoreApi/Utilities/QuantityLimits.php
@@ -16,12 +16,70 @@ class QuantityLimits {
 	use DraftOrderTrait;
 
 	/**
-	 * Check that a given quantity is valid according to any limits in place.
+	 * Get quantity limits (min, max, step/multiple) for a product or cart item.
 	 *
-	 * @param integer           $quantity Quantity to validate.
 	 * @param \WC_Product|array $cart_item_or_product Either a cart item or a product instance.
-	 * @return \WP_Error|true
+	 * @return object
 	 */
+	public function get_quantity_limits( $cart_item_or_product ) {
+		$product = $cart_item_or_product instanceof \WC_Product ? $cart_item_or_product : $cart_item_or_product['data'];
+
+		if ( ! $product instanceof \WC_Product ) {
+			return [
+				'minimum'     => 1,
+				'maximum'     => null,
+				'multiple_of' => 1,
+			];
+		}
+
+		$multiple_of = $this->filter_value( 1, 'multiple_of', $cart_item_or_product );
+		$minimum     = $this->filter_value( 1, 'minimum', $cart_item_or_product );
+		$maximum     = $this->filter_value( $this->get_product_quantity_limit( $product ), 'maximum', $cart_item_or_product );
+
+		return (object) [
+			'minimum'     => $this->limit_to_multiple( $minimum, $multiple_of, 'ceil' ),
+			'maximum'     => $this->limit_to_multiple( $maximum, $multiple_of, 'floor' ),
+			'multiple_of' => $multiple_of,
+		];
+	}
+
+	/**
+	 * Get the limit for the total number of a product allowed in the cart.
+	 *
+	 * This is based on product properties, including remaining stock, and defaults to a maximum of 99 of any product
+	 * in the cart at once.
+	 *
+	 * @param \WC_Product $product Product instance.
+	 * @return int
+	 */
+	protected function get_product_quantity_limit( \WC_Product $product ) {
+		$limits = [ 99 ];
+
+		if ( $product->is_sold_individually() ) {
+			$limits[] = 1;
+		} elseif ( ! $product->backorders_allowed() ) {
+			$limits[] = $this->get_remaining_stock( $product );
+		}
+
+		/**
+		 * Filters the quantity limit for a product being added to the cart via the Store API.
+		 *
+		 * Filters the variation option name for custom option slugs.
+		 *
+		 * @param integer $quantity_limit Quantity limit which defaults to 99 unless sold individually.
+		 * @param \WC_Product $product Product instance.
+		 * @return integer
+		 */
+		return apply_filters( 'woocommerce_store_api_product_quantity_limit', max( min( array_filter( $limits ) ), 1 ), $product );
+	}
+
+		/**
+		 * Check that a given quantity is valid according to any limits in place.
+		 *
+		 * @param integer           $quantity Quantity to validate.
+		 * @param \WC_Product|array $cart_item_or_product Either a cart item or a product instance.
+		 * @return \WP_Error|true
+		 */
 	public function validate_quantity( $quantity, $cart_item_or_product ) {
 		$limits = $this->get_quantity_limits( $cart_item_or_product );
 
@@ -61,35 +119,6 @@ public function validate_quantity( $quantity, $cart_item_or_product ) {
 		return true;
 	}
 
-	/**
-	 * Get quantity limits (min, max, step/multiple) for a product or cart item.
-	 *
-	 * @param \WC_Product|array $cart_item_or_product Either a cart item or a product instance.
-	 * @return object
-	 */
-	public function get_quantity_limits( $cart_item_or_product ) {
-		$product = $cart_item_or_product instanceof \WC_Product ? $cart_item_or_product : $cart_item_or_product['data'];
-
-		if ( ! $product instanceof \WC_Product ) {
-			return [
-				'minimum'     => 1,
-				'maximum'     => null,
-				'multiple_of' => 1,
-			];
-		}
-
-		$product_limit = $product->is_sold_individually() ? 1 : $this->get_remaining_stock( $product );
-		$multiple_of   = $this->filter_value( 1, 'multiple_of', $cart_item_or_product );
-		$minimum       = $this->filter_value( 1, 'minimum', $cart_item_or_product );
-		$maximum       = $this->filter_value( $product_limit ? $product_limit : $this->limit_to_multiple( 99, $multiple_of, 'ceil' ), 'maximum', $cart_item_or_product );
-
-		return (object) [
-			'minimum'     => $this->limit_to_multiple( $minimum, $multiple_of, 'ceil' ),
-			'maximum'     => $this->limit_to_multiple( $maximum, $multiple_of, 'floor' ),
-			'multiple_of' => $multiple_of,
-		];
-	}
-
 	/**
 	 * Returns the remaining stock for a product if it has stock.
 	 *
@@ -109,6 +138,22 @@ protected function get_remaining_stock( \WC_Product $product ) {
 		return $product->get_stock_quantity() - $reserved_stock;
 	}
 
+	/**
+	 * Return a number using the closest multiple of another number. Used to enforce step/multiple values.
+	 *
+	 * @param int    $number Number to round.
+	 * @param int    $multiple_of The multiple.
+	 * @param string $rounding_function ceil, floor, or round.
+	 * @return int
+	 */
+	protected function limit_to_multiple( int $number, int $multiple_of, string $rounding_function = 'ceil' ) {
+		if ( $multiple_of <= 1 ) {
+			return $number;
+		}
+		$rounding_function = in_array( $rounding_function, [ 'ceil', 'floor', 'round' ], true ) ? $rounding_function : 'round';
+		return $rounding_function( $number / $multiple_of ) * $multiple_of;
+	}
+
 	/**
 	 * Get a quantity for a product or cart item by running it through a filter hook.
 	 *
@@ -133,20 +178,4 @@ protected function filter_value( $value, string $value_type, $cart_item_or_produ
 		 */
 		return (int) apply_filters( "woocommerce_store_api_{$type}_quantity_{$value_type}", $value, $cart_item_or_product );
 	}
-
-	/**
-	 * Return a number using the closest multiple of another number. Used to enforce step/multiple values.
-	 *
-	 * @param int    $number Number to round.
-	 * @param int    $multiple_of The multiple.
-	 * @param string $rounding_function ceil, floor, or round.
-	 * @return int
-	 */
-	protected function limit_to_multiple( int $number, int $multiple_of, string $rounding_function = 'ceil' ) {
-		if ( $multiple_of <= 1 ) {
-			return $number;
-		}
-		$rounding_function = in_array( $rounding_function, [ 'ceil', 'floor', 'round' ], true ) ? $rounding_function : 'round';
-		return $rounding_function( $number / $multiple_of ) * $multiple_of;
-	}
 }
diff --git a/src/StoreApi/docs/cart-items.md b/src/StoreApi/docs/cart-items.md
index 272238b2da8..8d9b6cc5903 100644
--- a/src/StoreApi/docs/cart-items.md
+++ b/src/StoreApi/docs/cart-items.md
@@ -203,7 +203,11 @@ curl "https://example-store.com/wp-json/wc/store/cart/items/e369853df766fa44e1ed
 	"key": "e369853df766fa44e1ed0ff613f563bd",
 	"id": 34,
 	"quantity": 1,
-	"quantity_limit": 99,
+	"quantity_limits": {
+		"minimum": 1,
+		"maximum": 99,
+		"multiple_of": 1
+	},
 	"name": "WordPress Pennant",
 	"summary": "<p>This is an external product.</p>",
 	"short_description": "<p>This is an external product.</p>",

From 22ce1a233b77cd6e87175814b95566273dad6c8e Mon Sep 17 00:00:00 2001
From: Mike Jolley <mike.jolley@me.com>
Date: Fri, 17 Dec 2021 12:36:09 +0000
Subject: [PATCH 11/17] Normalize on + -

---
 assets/js/base/components/quantity-selector/index.tsx | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/assets/js/base/components/quantity-selector/index.tsx b/assets/js/base/components/quantity-selector/index.tsx
index b16ca2ccdc6..5b58b219f16 100644
--- a/assets/js/base/components/quantity-selector/index.tsx
+++ b/assets/js/base/components/quantity-selector/index.tsx
@@ -85,7 +85,7 @@ const QuantitySelector = ( {
 			// We copy the starting value.
 			let value = initialValue;
 
-			// We check if we have a maximum value, and select the lowest between what was inserted, and the maximum.
+			// We check if we have a maximum value, and select the lowest between what was inserted and the maximum.
 			if ( hasMaximum ) {
 				value = Math.min(
 					value,
@@ -159,7 +159,7 @@ const QuantitySelector = ( {
 					if ( value !== quantity ) {
 						// we commit this value immediately.
 						onChange( value );
-						// but once the customer has stopped typing, we make sure his value is respecting the bounds (maximum value, minimum value, step value), and commit the normlized value.
+						// but once the customer has stopped typing, we make sure his value is respecting the bounds (maximum value, minimum value, step value), and commit the normalized value.
 						normalizeQuantity( value );
 					}
 				} }
@@ -192,6 +192,7 @@ const QuantitySelector = ( {
 							newQuantity
 						)
 					);
+					normalizeQuantity( newQuantity );
 				} }
 			>
 				{ step === 1 || quantity < step ? `－` : quantity - step }
@@ -216,6 +217,7 @@ const QuantitySelector = ( {
 							newQuantity
 						)
 					);
+					normalizeQuantity( newQuantity );
 				} }
 			>
 				{ step === 1 ? '＋' : quantity + step }

From 8dff27eabed753b487d78f733b32ba6b8f70cc25 Mon Sep 17 00:00:00 2001
From: Mike Jolley <mike.jolley@me.com>
Date: Fri, 17 Dec 2021 17:14:36 +0000
Subject: [PATCH 12/17] Separate add to cart events from cart item events in
 regards to limits

---
 .../add-to-cart/product-types/simple.js       |   2 +
 .../product-types/variable/index.js           |   2 +
 .../add-to-cart/shared/quantity-input.js      |  48 +++++-
 .../add-to-cart-form/form-state/constants.js  |   2 +-
 .../add-to-cart-form/form-state/index.js      |   8 +-
 .../cart-line-item-row.tsx                    |   3 +-
 .../js/shared/context/product-data-context.js |   8 +-
 assets/js/types/type-defs/cart.ts             |   1 +
 assets/js/types/type-defs/product-response.ts |   8 +-
 src/StoreApi/Schemas/CartItemSchema.php       |  13 +-
 src/StoreApi/Schemas/ProductSchema.php        |  58 +++----
 src/StoreApi/Utilities/CartController.php     |  24 +--
 src/StoreApi/Utilities/QuantityLimits.php     | 149 ++++++++++--------
 src/StoreApi/docs/cart-items.md               |   9 +-
 src/StoreApi/docs/cart.md                     |   6 +-
 15 files changed, 213 insertions(+), 128 deletions(-)

diff --git a/assets/js/atomic/blocks/product-elements/add-to-cart/product-types/simple.js b/assets/js/atomic/blocks/product-elements/add-to-cart/product-types/simple.js
index a08fe69ee38..ce3670bcd36 100644
--- a/assets/js/atomic/blocks/product-elements/add-to-cart/product-types/simple.js
+++ b/assets/js/atomic/blocks/product-elements/add-to-cart/product-types/simple.js
@@ -18,6 +18,7 @@ const Simple = () => {
 		quantity,
 		minQuantity,
 		maxQuantity,
+		multipleOf,
 		dispatchActions,
 		isDisabled,
 	} = useAddToCartFormContext();
@@ -43,6 +44,7 @@ const Simple = () => {
 				value={ quantity }
 				min={ minQuantity }
 				max={ maxQuantity }
+				step={ multipleOf }
 				disabled={ isDisabled }
 				onChange={ dispatchActions.setQuantity }
 			/>
diff --git a/assets/js/atomic/blocks/product-elements/add-to-cart/product-types/variable/index.js b/assets/js/atomic/blocks/product-elements/add-to-cart/product-types/variable/index.js
index fb7d707e306..4cc5e9e16fd 100644
--- a/assets/js/atomic/blocks/product-elements/add-to-cart/product-types/variable/index.js
+++ b/assets/js/atomic/blocks/product-elements/add-to-cart/product-types/variable/index.js
@@ -23,6 +23,7 @@ const Variable = () => {
 		quantity,
 		minQuantity,
 		maxQuantity,
+		multipleOf,
 		dispatchActions,
 		isDisabled,
 	} = useAddToCartFormContext();
@@ -52,6 +53,7 @@ const Variable = () => {
 				value={ quantity }
 				min={ minQuantity }
 				max={ maxQuantity }
+				step={ multipleOf }
 				disabled={ isDisabled }
 				onChange={ dispatchActions.setQuantity }
 			/>
diff --git a/assets/js/atomic/blocks/product-elements/add-to-cart/shared/quantity-input.js b/assets/js/atomic/blocks/product-elements/add-to-cart/shared/quantity-input.js
index 5f275ab98ac..a58a7250ada 100644
--- a/assets/js/atomic/blocks/product-elements/add-to-cart/shared/quantity-input.js
+++ b/assets/js/atomic/blocks/product-elements/add-to-cart/shared/quantity-input.js
@@ -1,3 +1,8 @@
+/**
+ * External dependencies
+ */
+import { useDebouncedCallback } from 'use-debounce';
+
 /**
  * Quantity Input Component.
  *
@@ -5,10 +10,49 @@
  * @param {boolean}        props.disabled Whether input is disabled or not.
  * @param {number}         props.min      Minimum value for input.
  * @param {number}         props.max      Maximum value for input.
+ * @param {number}         props.step Step attribute for input.
  * @param {number}         props.value    Value for input.
  * @param {function():any} props.onChange Function to call on input change event.
  */
-const QuantityInput = ( { disabled, min, max, value, onChange } ) => {
+const QuantityInput = ( { disabled, min, max, step = 1, value, onChange } ) => {
+	const hasMaximum = typeof max !== 'undefined';
+
+	/**
+	 * The goal of this function is to normalize what was inserted,
+	 * but after the customer has stopped typing.
+	 *
+	 * It's important to wait before normalizing or we end up with
+	 * a frustrating experience, for example, if the minimum is 2 and
+	 * the customer is trying to type "10", premature normalizing would
+	 * always kick in at "1" and turn that into 2.
+	 *
+	 * Copied from <QuantitySelector>
+	 */
+	const normalizeQuantity = useDebouncedCallback( ( initialValue ) => {
+		// We copy the starting value.
+		let newValue = initialValue;
+
+		// We check if we have a maximum value, and select the lowest between what was inserted and the maximum.
+		if ( hasMaximum ) {
+			newValue = Math.min(
+				newValue,
+				// the maximum possible value in step increments.
+				Math.floor( max / step ) * step
+			);
+		}
+
+		// Select the biggest between what's inserted, the the minimum value in steps.
+		newValue = Math.max( newValue, Math.ceil( min / step ) * step );
+
+		// We round off the value to our steps.
+		newValue = Math.floor( newValue / step ) * step;
+
+		// Only commit if the value has changed
+		if ( newValue !== initialValue ) {
+			onChange( newValue );
+		}
+	}, 300 );
+
 	return (
 		<input
 			className="wc-block-components-product-add-to-cart-quantity"
@@ -16,10 +60,12 @@ const QuantityInput = ( { disabled, min, max, value, onChange } ) => {
 			value={ value }
 			min={ min }
 			max={ max }
+			step={ step }
 			hidden={ max === 1 }
 			disabled={ disabled }
 			onChange={ ( e ) => {
 				onChange( e.target.value );
+				normalizeQuantity( e.target.value );
 			} }
 		/>
 	);
diff --git a/assets/js/base/context/providers/add-to-cart-form/form-state/constants.js b/assets/js/base/context/providers/add-to-cart-form/form-state/constants.js
index 9f3633ced93..c9ebea0b330 100644
--- a/assets/js/base/context/providers/add-to-cart-form/form-state/constants.js
+++ b/assets/js/base/context/providers/add-to-cart-form/form-state/constants.js
@@ -13,7 +13,7 @@ export const STATUS = {
 export const DEFAULT_STATE = {
 	status: STATUS.PRISTINE,
 	hasError: false,
-	quantity: 1,
+	quantity: 0,
 	processingResponse: null,
 	requestParams: {},
 };
diff --git a/assets/js/base/context/providers/add-to-cart-form/form-state/index.js b/assets/js/base/context/providers/add-to-cart-form/form-state/index.js
index 35508304322..b8438f0b46b 100644
--- a/assets/js/base/context/providers/add-to-cart-form/form-state/index.js
+++ b/assets/js/base/context/providers/add-to-cart-form/form-state/index.js
@@ -296,9 +296,11 @@ export const AddToCartFormStateContextProvider = ( {
 		productHasOptions: product.has_options || false,
 		supportsFormElements,
 		showFormElements: showFormElements && supportsFormElements,
-		quantity: addToCartFormState.quantity,
-		minQuantity: 1,
-		maxQuantity: product?.quantity_limits?.maximum || 99,
+		quantity:
+			addToCartFormState.quantity || product?.add_to_cart?.minimum || 1,
+		minQuantity: product?.add_to_cart?.minimum || 1,
+		maxQuantity: product?.add_to_cart?.maximum || 99,
+		multipleOf: product?.add_to_cart?.multiple_of || 1,
 		requestParams: addToCartFormState.requestParams,
 		isIdle: addToCartFormState.status === STATUS.IDLE,
 		isDisabled: addToCartFormState.status === STATUS.DISABLED,
diff --git a/assets/js/blocks/cart-checkout/cart/cart-line-items-table/cart-line-item-row.tsx b/assets/js/blocks/cart-checkout/cart/cart-line-items-table/cart-line-item-row.tsx
index 0e7132445eb..26894b8250a 100644
--- a/assets/js/blocks/cart-checkout/cart/cart-line-items-table/cart-line-item-row.tsx
+++ b/assets/js/blocks/cart-checkout/cart/cart-line-items-table/cart-line-item-row.tsx
@@ -74,6 +74,7 @@ const CartLineItemRow = forwardRef< HTMLTableRowElement, CartLineItemRowProps >(
 				minimum: 1,
 				maximum: 99,
 				multiple_of: 1,
+				editable: true,
 			},
 			sold_individually: soldIndividually = false,
 			permalink = '',
@@ -283,7 +284,7 @@ const CartLineItemRow = forwardRef< HTMLTableRowElement, CartLineItemRowProps >(
 					/>
 
 					<div className="wc-block-cart-item__quantity">
-						{ ! soldIndividually && (
+						{ ! soldIndividually && !! quantityLimits.editable && (
 							<QuantitySelector
 								disabled={ isPendingDelete }
 								quantity={ quantity }
diff --git a/assets/js/shared/context/product-data-context.js b/assets/js/shared/context/product-data-context.js
index c0fc1bd60f9..ef94a8eea79 100644
--- a/assets/js/shared/context/product-data-context.js
+++ b/assets/js/shared/context/product-data-context.js
@@ -45,15 +45,13 @@ const defaultProductData = {
 	is_on_backorder: false,
 	low_stock_remaining: null,
 	sold_individually: false,
-	quantity_limits: {
-		minimum: 1,
-		maximum: 99,
-		multiple_of: 1,
-	},
 	add_to_cart: {
 		text: 'Add to cart',
 		description: 'Add to cart',
 		url: '',
+		minimum: 1,
+		maximum: 99,
+		multiple_of: 1,
 	},
 };
 
diff --git a/assets/js/types/type-defs/cart.ts b/assets/js/types/type-defs/cart.ts
index f7ed32c2c43..e00d0a19d7a 100644
--- a/assets/js/types/type-defs/cart.ts
+++ b/assets/js/types/type-defs/cart.ts
@@ -121,6 +121,7 @@ export interface CartItem {
 		minimum: number;
 		maximum: number;
 		multiple_of: number;
+		editable: boolean;
 	};
 	name: string;
 	summary: string;
diff --git a/assets/js/types/type-defs/product-response.ts b/assets/js/types/type-defs/product-response.ts
index cac37d6473a..8c1d037bde5 100644
--- a/assets/js/types/type-defs/product-response.ts
+++ b/assets/js/types/type-defs/product-response.ts
@@ -86,14 +86,12 @@ export interface ProductResponseItem {
 	is_on_backorder: boolean;
 	low_stock_remaining: null | number;
 	sold_individually: boolean;
-	quantity_limits: {
-		minimum: number;
-		maximum: number;
-		multiple_of: number;
-	};
 	add_to_cart: {
 		text: string;
 		description: string;
 		url: string;
+		minimum: number;
+		maximum: number;
+		multiple_of: number;
 	};
 }
diff --git a/src/StoreApi/Schemas/CartItemSchema.php b/src/StoreApi/Schemas/CartItemSchema.php
index 746d0178966..bbf0bc060be 100644
--- a/src/StoreApi/Schemas/CartItemSchema.php
+++ b/src/StoreApi/Schemas/CartItemSchema.php
@@ -53,7 +53,7 @@ public function get_properties() {
 			],
 			'quantity_limits'      => [
 				'description' => __( 'How the quantity of this item should be controlled, for example, any limits in place.', 'woo-gutenberg-products-block' ),
-				'type'        => [ 'object', 'boolean' ],
+				'type'        => 'object',
 				'context'     => [ 'view', 'edit' ],
 				'readonly'    => true,
 				'properties'  => [
@@ -70,12 +70,19 @@ public function get_properties() {
 						'readonly'    => true,
 					],
 					'multiple_of' => [
-						'description' => __( 'The amount that quantities increment by. Quantity must be an increment of this value.', 'woo-gutenberg-products-block' ),
+						'description' => __( 'The amount that quantities increment by. Quantity must be an multiple of this value.', 'woo-gutenberg-products-block' ),
 						'type'        => 'integer',
 						'context'     => [ 'view', 'edit' ],
 						'readonly'    => true,
 						'default'     => 1,
 					],
+					'editable'    => [
+						'description' => __( 'If the quantity in the cart is editable or fixed.', 'woo-gutenberg-products-block' ),
+						'type'        => 'boolean',
+						'context'     => [ 'view', 'edit' ],
+						'readonly'    => true,
+						'default'     => true,
+					],
 				],
 			],
 			'name'                 => [
@@ -334,7 +341,7 @@ public function get_item_response( $cart_item ) {
 			'key'                  => $cart_item['key'],
 			'id'                   => $product->get_id(),
 			'quantity'             => wc_stock_amount( $cart_item['quantity'] ),
-			'quantity_limits'      => ( new QuantityLimits() )->get_quantity_limits( $cart_item ),
+			'quantity_limits'      => (object) ( new QuantityLimits() )->get_quantity_limits( $cart_item ),
 			'name'                 => $this->prepare_html_response( $product->get_title() ),
 			'short_description'    => $this->prepare_html_response( wc_format_content( wp_kses_post( $product->get_short_description() ) ) ),
 			'description'          => $this->prepare_html_response( wc_format_content( wp_kses_post( $product->get_description() ) ) ),
diff --git a/src/StoreApi/Schemas/ProductSchema.php b/src/StoreApi/Schemas/ProductSchema.php
index a1f86f0103f..fbcae6fde03 100644
--- a/src/StoreApi/Schemas/ProductSchema.php
+++ b/src/StoreApi/Schemas/ProductSchema.php
@@ -392,33 +392,6 @@ public function get_properties() {
 				'context'     => [ 'view', 'edit' ],
 				'readonly'    => true,
 			],
-			'quantity_limits'     => [
-				'description' => __( 'How the quantity of this item should be controlled, for example, any limits in place.', 'woo-gutenberg-products-block' ),
-				'type'        => [ 'object', 'boolean' ],
-				'context'     => [ 'view', 'edit' ],
-				'readonly'    => true,
-				'properties'  => [
-					'minimum'     => [
-						'description' => __( 'The minimum quantity allowed in the cart for this line item.', 'woo-gutenberg-products-block' ),
-						'type'        => 'integer',
-						'context'     => [ 'view', 'edit' ],
-						'readonly'    => true,
-					],
-					'maximum'     => [
-						'description' => __( 'The maximum quantity allowed in the cart for this line item.', 'woo-gutenberg-products-block' ),
-						'type'        => 'integer',
-						'context'     => [ 'view', 'edit' ],
-						'readonly'    => true,
-					],
-					'multiple_of' => [
-						'description' => __( 'The amount that quantities increment by. Quantity must be an increment of this value.', 'woo-gutenberg-products-block' ),
-						'type'        => 'integer',
-						'context'     => [ 'view', 'edit' ],
-						'readonly'    => true,
-						'default'     => 1,
-					],
-				],
-			],
 			'add_to_cart'         => [
 				'description' => __( 'Add to cart button parameters.', 'woo-gutenberg-products-block' ),
 				'type'        => 'object',
@@ -443,6 +416,25 @@ public function get_properties() {
 						'context'     => [ 'view', 'edit' ],
 						'readonly'    => true,
 					],
+					'minimum'     => [
+						'description' => __( 'The minimum quantity that can be added to the cart.', 'woo-gutenberg-products-block' ),
+						'type'        => 'integer',
+						'context'     => [ 'view', 'edit' ],
+						'readonly'    => true,
+					],
+					'maximum'     => [
+						'description' => __( 'The maximum quantity that can be added to the cart.', 'woo-gutenberg-products-block' ),
+						'type'        => 'integer',
+						'context'     => [ 'view', 'edit' ],
+						'readonly'    => true,
+					],
+					'multiple_of' => [
+						'description' => __( 'The amount that quantities increment by. Quantity must be an multiple of this value.', 'woo-gutenberg-products-block' ),
+						'type'        => 'integer',
+						'context'     => [ 'view', 'edit' ],
+						'readonly'    => true,
+						'default'     => 1,
+					],
 				],
 			],
 		];
@@ -481,13 +473,13 @@ public function get_item_response( $product ) {
 			'is_on_backorder'     => 'onbackorder' === $product->get_stock_status(),
 			'low_stock_remaining' => $this->get_low_stock_remaining( $product ),
 			'sold_individually'   => $product->is_sold_individually(),
-			'quantity_limits'     => ( new QuantityLimits() )->get_quantity_limits( $product ),
-			'add_to_cart'         => (object) $this->prepare_html_response(
+			'add_to_cart'         => (object) array_merge(
 				[
-					'text'        => $product->add_to_cart_text(),
-					'description' => $product->add_to_cart_description(),
-					'url'         => $product->add_to_cart_url(),
-				]
+					'text'        => $this->prepare_html_response( $product->add_to_cart_text() ),
+					'description' => $this->prepare_html_response( $product->add_to_cart_description() ),
+					'url'         => $this->prepare_html_response( $product->add_to_cart_url() ),
+				],
+				( new QuantityLimits() )->get_add_to_cart_limits( $product )
 			),
 		];
 	}
diff --git a/src/StoreApi/Utilities/CartController.php b/src/StoreApi/Utilities/CartController.php
index 6224fc23c3c..11015caf65c 100644
--- a/src/StoreApi/Utilities/CartController.php
+++ b/src/StoreApi/Utilities/CartController.php
@@ -63,11 +63,12 @@ public function add_to_cart( $request ) {
 
 		$this->validate_add_to_cart( $product, $request );
 
+		$quantity_limits  = new QuantityLimits();
 		$existing_cart_id = $cart->find_product_in_cart( $cart_id );
 
 		if ( $existing_cart_id ) {
 			$cart_item           = $cart->cart_contents[ $existing_cart_id ];
-			$quantity_validation = ( new QuantityLimits() )->validate_quantity( $request['quantity'] + $cart_item['quantity'], $cart_item );
+			$quantity_validation = $quantity_limits->validate_quantity( $request['quantity'] + $cart_item['quantity'], $cart_item );
 
 			if ( is_wp_error( $quantity_validation ) ) {
 				throw new RouteException( $quantity_validation->get_error_code(), $quantity_validation->get_error_message(), 400 );
@@ -76,14 +77,19 @@ public function add_to_cart( $request ) {
 			$cart->set_quantity( $existing_cart_id, $request['quantity'] + $cart->cart_contents[ $existing_cart_id ]['quantity'], true );
 
 			return $existing_cart_id;
-		} else {
-			$quantity_validation = ( new QuantityLimits() )->validate_quantity( $request['quantity'], $product );
+		}
 
-			if ( is_wp_error( $quantity_validation ) ) {
-				throw new RouteException( $quantity_validation->get_error_code(), $quantity_validation->get_error_message(), 400 );
-			}
+		// Normalize quantity.
+		$add_to_cart_limits = $quantity_limits->get_add_to_cart_limits( $product );
+		$request_quantity   = (int) $request['quantity'];
+
+		if ( $add_to_cart_limits['maximum'] ) {
+			$request_quantity = min( $request_quantity, $add_to_cart_limits['maximum'] );
 		}
 
+		$request_quantity = max( $request_quantity, $add_to_cart_limits['minimum'] );
+		$request_quantity = $quantity_limits->limit_to_multiple( $request_quantity, $add_to_cart_limits['multiple_of'] );
+
 		/**
 		 * Filters the item being added to the cart.
 		 *
@@ -100,7 +106,7 @@ public function add_to_cart( $request ) {
 					'product_id'   => $this->get_product_id( $product ),
 					'variation_id' => $this->get_variation_id( $product ),
 					'variation'    => $request['variation'],
-					'quantity'     => $request['quantity'],
+					'quantity'     => $request_quantity,
 					'data'         => $product,
 					'data_hash'    => wc_get_cart_item_data_hash( $product ),
 				)
@@ -124,7 +130,7 @@ public function add_to_cart( $request ) {
 		 *
 		 * @param string $cart_id ID of the item in the cart.
 		 * @param integer $product_id ID of the product added to the cart.
-		 * @param integer $quantity Quantity of the item added to the cart.
+		 * @param integer $request_quantity Quantity of the item added to the cart.
 		 * @param integer $variation_id Variation ID of the product added to the cart.
 		 * @param array $variation Array of variation data.
 		 * @param array $cart_item_data Array of other cart item data.
@@ -133,7 +139,7 @@ public function add_to_cart( $request ) {
 			'woocommerce_add_to_cart',
 			$cart_id,
 			$this->get_product_id( $product ),
-			$request['quantity'],
+			$request_quantity,
 			$this->get_variation_id( $product ),
 			$request['variation'],
 			$request['cart_item_data']
diff --git a/src/StoreApi/Utilities/QuantityLimits.php b/src/StoreApi/Utilities/QuantityLimits.php
index 3cf2e8545ea..6a3237762aa 100644
--- a/src/StoreApi/Utilities/QuantityLimits.php
+++ b/src/StoreApi/Utilities/QuantityLimits.php
@@ -12,106 +12,117 @@
  * @internal This API is used internally by Blocks--it is still in flux and may be subject to revisions.
  * @since 2.5.0
  */
-class QuantityLimits {
+final class QuantityLimits {
 	use DraftOrderTrait;
 
 	/**
 	 * Get quantity limits (min, max, step/multiple) for a product or cart item.
 	 *
-	 * @param \WC_Product|array $cart_item_or_product Either a cart item or a product instance.
-	 * @return object
+	 * @param array $cart_item A cart item array.
+	 * @return array
 	 */
-	public function get_quantity_limits( $cart_item_or_product ) {
-		$product = $cart_item_or_product instanceof \WC_Product ? $cart_item_or_product : $cart_item_or_product['data'];
+	public function get_quantity_limits( $cart_item ) {
+		$product = $cart_item['data'] ?? false;
 
 		if ( ! $product instanceof \WC_Product ) {
 			return [
 				'minimum'     => 1,
 				'maximum'     => null,
 				'multiple_of' => 1,
+				'editable'    => true,
 			];
 		}
 
-		$multiple_of = $this->filter_value( 1, 'multiple_of', $cart_item_or_product );
-		$minimum     = $this->filter_value( 1, 'minimum', $cart_item_or_product );
-		$maximum     = $this->filter_value( $this->get_product_quantity_limit( $product ), 'maximum', $cart_item_or_product );
+		$multiple_of = (int) $this->filter_value( 1, 'multiple_of', $cart_item );
+		$minimum     = (int) $this->filter_value( 1, 'minimum', $cart_item );
+		$maximum     = (int) $this->filter_value( $this->get_product_quantity_limit( $product ), 'maximum', $cart_item );
+		$editable    = (bool) $this->filter_value( ! $product->is_sold_individually(), 'editable', $cart_item );
 
-		return (object) [
+		return [
 			'minimum'     => $this->limit_to_multiple( $minimum, $multiple_of, 'ceil' ),
 			'maximum'     => $this->limit_to_multiple( $maximum, $multiple_of, 'floor' ),
 			'multiple_of' => $multiple_of,
+			'editable'    => $editable,
 		];
 	}
 
 	/**
-	 * Get the limit for the total number of a product allowed in the cart.
-	 *
-	 * This is based on product properties, including remaining stock, and defaults to a maximum of 99 of any product
-	 * in the cart at once.
+	 * Get limits for product add to cart forms.
 	 *
 	 * @param \WC_Product $product Product instance.
-	 * @return int
+	 * @return array
 	 */
-	protected function get_product_quantity_limit( \WC_Product $product ) {
-		$limits = [ 99 ];
+	public function get_add_to_cart_limits( \WC_Product $product ) {
+		$multiple_of = $this->filter_value( 1, 'multiple_of', $product );
+		$minimum     = $this->filter_value( 1, 'minimum', $product );
+		$maximum     = $this->filter_value( $this->get_product_quantity_limit( $product ), 'maximum', $product );
 
-		if ( $product->is_sold_individually() ) {
-			$limits[] = 1;
-		} elseif ( ! $product->backorders_allowed() ) {
-			$limits[] = $this->get_remaining_stock( $product );
-		}
+		return [
+			'minimum'     => $this->limit_to_multiple( $minimum, $multiple_of, 'ceil' ),
+			'maximum'     => $this->limit_to_multiple( $maximum, $multiple_of, 'floor' ),
+			'multiple_of' => $multiple_of,
+		];
+	}
 
-		/**
-		 * Filters the quantity limit for a product being added to the cart via the Store API.
-		 *
-		 * Filters the variation option name for custom option slugs.
-		 *
-		 * @param integer $quantity_limit Quantity limit which defaults to 99 unless sold individually.
-		 * @param \WC_Product $product Product instance.
-		 * @return integer
-		 */
-		return apply_filters( 'woocommerce_store_api_product_quantity_limit', max( min( array_filter( $limits ) ), 1 ), $product );
+	/**
+	 * Return a number using the closest multiple of another number. Used to enforce step/multiple values.
+	 *
+	 * @param int    $number Number to round.
+	 * @param int    $multiple_of The multiple.
+	 * @param string $rounding_function ceil, floor, or round.
+	 * @return int
+	 */
+	public function limit_to_multiple( int $number, int $multiple_of, string $rounding_function = 'round' ) {
+		if ( $multiple_of <= 1 ) {
+			return $number;
+		}
+		$rounding_function = in_array( $rounding_function, [ 'ceil', 'floor', 'round' ], true ) ? $rounding_function : 'round';
+		return $rounding_function( $number / $multiple_of ) * $multiple_of;
 	}
 
-		/**
-		 * Check that a given quantity is valid according to any limits in place.
-		 *
-		 * @param integer           $quantity Quantity to validate.
-		 * @param \WC_Product|array $cart_item_or_product Either a cart item or a product instance.
-		 * @return \WP_Error|true
-		 */
+	/**
+	 * Check that a given quantity is valid according to any limits in place.
+	 *
+	 * @param integer           $quantity Quantity to validate.
+	 * @param \WC_Product|array $cart_item_or_product Either a cart item or a product instance.
+	 * @return \WP_Error|true
+	 */
 	public function validate_quantity( $quantity, $cart_item_or_product ) {
 		$limits = $this->get_quantity_limits( $cart_item_or_product );
 
-		if ( $quantity < $limits->minimum ) {
+		if ( ! $limits ) {
+			return true;
+		}
+
+		if ( $quantity < $limits['minimum'] ) {
 			return new \WP_Error(
 				'invalid_quantity',
 				sprintf(
 					// Translators: %s amount.
 					__( 'The minimum quantity that can be added to the cart is %s', 'woo-gutenberg-products-block' ),
-					$limits->minimum
+					$limits['minimum']
 				)
 			);
 		}
 
-		if ( $quantity > $limits->maximum ) {
+		if ( $quantity > $limits['maximum'] ) {
 			return new \WP_Error(
 				'invalid_quantity',
 				sprintf(
 					// Translators: %s amount.
 					__( 'The maximum quantity that can be added to the cart is %s', 'woo-gutenberg-products-block' ),
-					$limits->maximum
+					$limits['maximum']
 				)
 			);
 		}
 
-		if ( $quantity % $limits->multiple_of ) {
+		if ( $quantity % $limits['multiple_of'] ) {
 			return new \WP_Error(
 				'invalid_quantity',
 				sprintf(
 					// Translators: %s amount.
 					__( 'The quantity added to the cart must be a multiple of %s', 'woo-gutenberg-products-block' ),
-					$limits->multiple_of
+					$limits['multiple_of']
 				)
 			);
 		}
@@ -119,6 +130,36 @@ public function validate_quantity( $quantity, $cart_item_or_product ) {
 		return true;
 	}
 
+	/**
+	 * Get the limit for the total number of a product allowed in the cart.
+	 *
+	 * This is based on product properties, including remaining stock, and defaults to a maximum of 99 of any product
+	 * in the cart at once.
+	 *
+	 * @param \WC_Product $product Product instance.
+	 * @return int
+	 */
+	protected function get_product_quantity_limit( \WC_Product $product ) {
+		$limits = [ 99 ];
+
+		if ( $product->is_sold_individually() ) {
+			$limits[] = 1;
+		} elseif ( ! $product->backorders_allowed() ) {
+			$limits[] = $this->get_remaining_stock( $product );
+		}
+
+		/**
+		 * Filters the quantity limit for a product being added to the cart via the Store API.
+		 *
+		 * Filters the variation option name for custom option slugs.
+		 *
+		 * @param integer $quantity_limit Quantity limit which defaults to 99 unless sold individually.
+		 * @param \WC_Product $product Product instance.
+		 * @return integer
+		 */
+		return apply_filters( 'woocommerce_store_api_product_quantity_limit', max( min( array_filter( $limits ) ), 1 ), $product );
+	}
+
 	/**
 	 * Returns the remaining stock for a product if it has stock.
 	 *
@@ -138,29 +179,13 @@ protected function get_remaining_stock( \WC_Product $product ) {
 		return $product->get_stock_quantity() - $reserved_stock;
 	}
 
-	/**
-	 * Return a number using the closest multiple of another number. Used to enforce step/multiple values.
-	 *
-	 * @param int    $number Number to round.
-	 * @param int    $multiple_of The multiple.
-	 * @param string $rounding_function ceil, floor, or round.
-	 * @return int
-	 */
-	protected function limit_to_multiple( int $number, int $multiple_of, string $rounding_function = 'ceil' ) {
-		if ( $multiple_of <= 1 ) {
-			return $number;
-		}
-		$rounding_function = in_array( $rounding_function, [ 'ceil', 'floor', 'round' ], true ) ? $rounding_function : 'round';
-		return $rounding_function( $number / $multiple_of ) * $multiple_of;
-	}
-
 	/**
 	 * Get a quantity for a product or cart item by running it through a filter hook.
 	 *
 	 * @param int|null          $value Value to filter.
 	 * @param string            $value_type Type of value. Used for filter suffix.
 	 * @param \WC_Product|array $cart_item_or_product Either a cart item or a product instance.
-	 * @return int|null
+	 * @return mixed
 	 */
 	protected function filter_value( $value, string $value_type, $cart_item_or_product ) {
 		$type = $cart_item_or_product instanceof \WC_Product ? 'product' : 'cart_item';
@@ -176,6 +201,6 @@ protected function filter_value( $value, string $value_type, $cart_item_or_produ
 		 * @param array $cart_item_or_product Product or cart item being added/updated in the cart.
 		 * @return integer
 		 */
-		return (int) apply_filters( "woocommerce_store_api_{$type}_quantity_{$value_type}", $value, $cart_item_or_product );
+		return apply_filters( "woocommerce_store_api_{$type}_quantity_{$value_type}", $value, $cart_item_or_product );
 	}
 }
diff --git a/src/StoreApi/docs/cart-items.md b/src/StoreApi/docs/cart-items.md
index 8d9b6cc5903..8c9ce3bbc6b 100644
--- a/src/StoreApi/docs/cart-items.md
+++ b/src/StoreApi/docs/cart-items.md
@@ -30,7 +30,8 @@ curl "https://example-store.com/wp-json/wc/store/cart/items"
 		"quantity_limits": {
 			"minimum": 1,
 			"maximum": 99,
-			"multiple_of": 1
+			"multiple_of": 1,
+			"editable": true
 		},
 		"name": "Beanie",
 		"summary": "<p>This is a simple product.</p>",
@@ -107,7 +108,8 @@ curl "https://example-store.com/wp-json/wc/store/cart/items"
 		"quantity_limits": {
 			"minimum": 1,
 			"maximum": 99,
-			"multiple_of": 1
+			"multiple_of": 1,
+			"editable": true
 		},
 		"name": "WordPress Pennant",
 		"summary": "<p>This is an external product.</p>",
@@ -206,7 +208,8 @@ curl "https://example-store.com/wp-json/wc/store/cart/items/e369853df766fa44e1ed
 	"quantity_limits": {
 		"minimum": 1,
 		"maximum": 99,
-		"multiple_of": 1
+		"multiple_of": 1,
+		"editable": true
 	},
 	"name": "WordPress Pennant",
 	"summary": "<p>This is an external product.</p>",
diff --git a/src/StoreApi/docs/cart.md b/src/StoreApi/docs/cart.md
index 9e27a28c2f5..a9828deda19 100644
--- a/src/StoreApi/docs/cart.md
+++ b/src/StoreApi/docs/cart.md
@@ -110,7 +110,8 @@ All endpoints under `/cart` (listed in this doc) return responses in the same fo
 			"quantity_limits": {
 				"minimum": 1,
 				"maximum": 99,
-				"multiple_of": 1
+				"multiple_of": 1,
+				"editable": true
 			},
 			"name": "Beanie",
 			"summary": "<p>This is a simple product.</p>",
@@ -174,7 +175,8 @@ All endpoints under `/cart` (listed in this doc) return responses in the same fo
 			"quantity_limits": {
 				"minimum": 1,
 				"maximum": 99,
-				"multiple_of": 1
+				"multiple_of": 1,
+				"editable": true
 			},
 			"name": "WordPress Pennant",
 			"summary": "<p>This is an external product.</p>",

From bcf13c8ecf3223277c714dbf5f0f1246fc3168c8 Mon Sep 17 00:00:00 2001
From: Mike Jolley <mike.jolley@me.com>
Date: Fri, 17 Dec 2021 17:23:05 +0000
Subject: [PATCH 13/17] Prevent qty change for editable line items

---
 src/StoreApi/Utilities/CartController.php |  4 ++--
 src/StoreApi/Utilities/QuantityLimits.php | 13 ++++++++-----
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/src/StoreApi/Utilities/CartController.php b/src/StoreApi/Utilities/CartController.php
index 11015caf65c..5689a30a080 100644
--- a/src/StoreApi/Utilities/CartController.php
+++ b/src/StoreApi/Utilities/CartController.php
@@ -68,7 +68,7 @@ public function add_to_cart( $request ) {
 
 		if ( $existing_cart_id ) {
 			$cart_item           = $cart->cart_contents[ $existing_cart_id ];
-			$quantity_validation = $quantity_limits->validate_quantity( $request['quantity'] + $cart_item['quantity'], $cart_item );
+			$quantity_validation = $quantity_limits->validate_cart_item_quantity( $request['quantity'] + $cart_item['quantity'], $cart_item );
 
 			if ( is_wp_error( $quantity_validation ) ) {
 				throw new RouteException( $quantity_validation->get_error_code(), $quantity_validation->get_error_message(), 400 );
@@ -170,7 +170,7 @@ public function set_cart_item_quantity( $item_id, $quantity = 1 ) {
 			throw new RouteException( 'woocommerce_rest_cart_invalid_product', __( 'Cart item is invalid.', 'woo-gutenberg-products-block' ), 404 );
 		}
 
-		$quantity_validation = ( new QuantityLimits() )->validate_quantity( $quantity, $cart_item );
+		$quantity_validation = ( new QuantityLimits() )->validate_cart_item_quantity( $quantity, $cart_item );
 
 		if ( is_wp_error( $quantity_validation ) ) {
 			throw new RouteException( $quantity_validation->get_error_code(), $quantity_validation->get_error_message(), 400 );
diff --git a/src/StoreApi/Utilities/QuantityLimits.php b/src/StoreApi/Utilities/QuantityLimits.php
index 6a3237762aa..0ed90165b8e 100644
--- a/src/StoreApi/Utilities/QuantityLimits.php
+++ b/src/StoreApi/Utilities/QuantityLimits.php
@@ -84,14 +84,17 @@ public function limit_to_multiple( int $number, int $multiple_of, string $roundi
 	 * Check that a given quantity is valid according to any limits in place.
 	 *
 	 * @param integer           $quantity Quantity to validate.
-	 * @param \WC_Product|array $cart_item_or_product Either a cart item or a product instance.
+	 * @param \WC_Product|array $cart_item Cart item.
 	 * @return \WP_Error|true
 	 */
-	public function validate_quantity( $quantity, $cart_item_or_product ) {
-		$limits = $this->get_quantity_limits( $cart_item_or_product );
+	public function validate_cart_item_quantity( $quantity, $cart_item ) {
+		$limits = $this->get_quantity_limits( $cart_item );
 
-		if ( ! $limits ) {
-			return true;
+		if ( ! $limits['editable'] ) {
+			return new \WP_Error(
+				'readonly_quantity',
+				__( 'This item is already in the cart and it\'s quantity cannot be edited', 'woo-gutenberg-products-block' )
+			);
 		}
 
 		if ( $quantity < $limits['minimum'] ) {

From 73bbd979a6d7117c5cfa9782808219d5c968defc Mon Sep 17 00:00:00 2001
From: Mike Jolley <mike.jolley@me.com>
Date: Fri, 17 Dec 2021 17:33:30 +0000
Subject: [PATCH 14/17] Unify filters

---
 bin/hook-docs/data/actions.json           |  2 +-
 docs/extensibility/actions.md             |  4 ++--
 src/StoreApi/Schemas/CartItemSchema.php   |  2 +-
 src/StoreApi/Utilities/QuantityLimits.php | 22 ++++++++++++----------
 4 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/bin/hook-docs/data/actions.json b/bin/hook-docs/data/actions.json
index 2b5553e8697..1556fb4c4e7 100644
--- a/bin/hook-docs/data/actions.json
+++ b/bin/hook-docs/data/actions.json
@@ -31,7 +31,7 @@
                         "types": [
                             "integer"
                         ],
-                        "variable": "$quantity"
+                        "variable": "$request_quantity"
                     },
                     {
                         "name": "param",
diff --git a/docs/extensibility/actions.md b/docs/extensibility/actions.md
index 670f959602a..e514a3648d2 100644
--- a/docs/extensibility/actions.md
+++ b/docs/extensibility/actions.md
@@ -44,7 +44,7 @@
 Fires when an item is added to the cart.
 
 ```php
-do_action( 'woocommerce_add_to_cart', string $cart_id, integer $product_id, integer $quantity, integer $variation_id, array $variation, array $cart_item_data )
+do_action( 'woocommerce_add_to_cart', string $cart_id, integer $product_id, integer $request_quantity, integer $variation_id, array $variation, array $cart_item_data )
 ```
 
 ### Description
@@ -57,7 +57,7 @@ do_action( 'woocommerce_add_to_cart', string $cart_id, integer $product_id, inte
 | -------- | ---- | ----------- |
 | $cart_id | string | ID of the item in the cart. |
 | $product_id | integer | ID of the product added to the cart. |
-| $quantity | integer | Quantity of the item added to the cart. |
+| $request_quantity | integer | Quantity of the item added to the cart. |
 | $variation_id | integer | Variation ID of the product added to the cart. |
 | $variation | array | Array of variation data. |
 | $cart_item_data | array | Array of other cart item data. |
diff --git a/src/StoreApi/Schemas/CartItemSchema.php b/src/StoreApi/Schemas/CartItemSchema.php
index bbf0bc060be..ba6ab3fe002 100644
--- a/src/StoreApi/Schemas/CartItemSchema.php
+++ b/src/StoreApi/Schemas/CartItemSchema.php
@@ -341,7 +341,7 @@ public function get_item_response( $cart_item ) {
 			'key'                  => $cart_item['key'],
 			'id'                   => $product->get_id(),
 			'quantity'             => wc_stock_amount( $cart_item['quantity'] ),
-			'quantity_limits'      => (object) ( new QuantityLimits() )->get_quantity_limits( $cart_item ),
+			'quantity_limits'      => (object) ( new QuantityLimits() )->get_cart_item_quantity_limits( $cart_item ),
 			'name'                 => $this->prepare_html_response( $product->get_title() ),
 			'short_description'    => $this->prepare_html_response( wc_format_content( wp_kses_post( $product->get_short_description() ) ) ),
 			'description'          => $this->prepare_html_response( wc_format_content( wp_kses_post( $product->get_description() ) ) ),
diff --git a/src/StoreApi/Utilities/QuantityLimits.php b/src/StoreApi/Utilities/QuantityLimits.php
index 0ed90165b8e..f6a8f8bea41 100644
--- a/src/StoreApi/Utilities/QuantityLimits.php
+++ b/src/StoreApi/Utilities/QuantityLimits.php
@@ -21,7 +21,7 @@ final class QuantityLimits {
 	 * @param array $cart_item A cart item array.
 	 * @return array
 	 */
-	public function get_quantity_limits( $cart_item ) {
+	public function get_cart_item_quantity_limits( $cart_item ) {
 		$product = $cart_item['data'] ?? false;
 
 		if ( ! $product instanceof \WC_Product ) {
@@ -88,7 +88,7 @@ public function limit_to_multiple( int $number, int $multiple_of, string $roundi
 	 * @return \WP_Error|true
 	 */
 	public function validate_cart_item_quantity( $quantity, $cart_item ) {
-		$limits = $this->get_quantity_limits( $cart_item );
+		$limits = $this->get_cart_item_quantity_limits( $cart_item );
 
 		if ( ! $limits['editable'] ) {
 			return new \WP_Error(
@@ -191,19 +191,21 @@ protected function get_remaining_stock( \WC_Product $product ) {
 	 * @return mixed
 	 */
 	protected function filter_value( $value, string $value_type, $cart_item_or_product ) {
-		$type = $cart_item_or_product instanceof \WC_Product ? 'product' : 'cart_item';
+		$is_product = $cart_item_or_product instanceof \WC_Product;
+		$product    = $is_product ? $cart_item_or_product : $cart_item_or_product['data'];
+		$cart_item  = $is_product ? null : $cart_item_or_product;
 		/**
 		 * Filters the quantity minimum for a cart item in Store API. This allows extensions to control the minimum qty
 		 * of items already within the cart.
 		 *
-		 * Hook name will reflect the product or cart item depending on what is provided, so either:
-		 *  - woocommerce_store_api_product_quantity_minimum
-		 *  - woocommerce_store_api_cart_item_quantity_minimum
+		 * The suffix of the hook will vary depending on the value being filtered.
+		 * For example, minimum, maximum, multiple_of, editable.
 		 *
-		 * @param integer $minimum Minimum qty which defaults to 1.
-		 * @param array $cart_item_or_product Product or cart item being added/updated in the cart.
-		 * @return integer
+		 * @param mixed $value The value being filtered.
+		 * @param \WC_Product $product The product object.
+		 * @param array|null $cart_item The cart item if the product exists in the cart, or null.
+		 * @return mixed
 		 */
-		return apply_filters( "woocommerce_store_api_{$type}_quantity_{$value_type}", $value, $cart_item_or_product );
+		return apply_filters( "woocommerce_store_api_product_quantity_{$value_type}", $value, $product, $cart_item );
 	}
 }

From 1220a3cff5d249526e852af3c4f3fd92ea6b9682 Mon Sep 17 00:00:00 2001
From: Mike Jolley <mike.jolley@me.com>
Date: Tue, 21 Dec 2021 14:38:42 +0000
Subject: [PATCH 15/17] =?UTF-8?q?Remove=20step=20number=20indicator=20from?=
 =?UTF-8?q?=20buttons=20=C2=AF\=5F(=E3=83=84)=5F/=C2=AF?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 assets/js/base/components/quantity-selector/index.tsx | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/assets/js/base/components/quantity-selector/index.tsx b/assets/js/base/components/quantity-selector/index.tsx
index 5b58b219f16..f84f795bb75 100644
--- a/assets/js/base/components/quantity-selector/index.tsx
+++ b/assets/js/base/components/quantity-selector/index.tsx
@@ -195,7 +195,7 @@ const QuantitySelector = ( {
 					normalizeQuantity( newQuantity );
 				} }
 			>
-				{ step === 1 || quantity < step ? `－` : quantity - step }
+				&#65293;
 			</button>
 			<button
 				aria-label={ __(
@@ -220,7 +220,7 @@ const QuantitySelector = ( {
 					normalizeQuantity( newQuantity );
 				} }
 			>
-				{ step === 1 ? '＋' : quantity + step }
+				&#65291;
 			</button>
 		</div>
 	);

From 75c4e200becd6fb9f941c66c188db699cb8f4a1b Mon Sep 17 00:00:00 2001
From: Mike Jolley <mike.jolley@me.com>
Date: Tue, 21 Dec 2021 14:46:56 +0000
Subject: [PATCH 16/17] Normalize on mount

---
 .../components/quantity-selector/index.tsx    | 29 ++++++++++++++-----
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/assets/js/base/components/quantity-selector/index.tsx b/assets/js/base/components/quantity-selector/index.tsx
index f84f795bb75..1076c3c6dd4 100644
--- a/assets/js/base/components/quantity-selector/index.tsx
+++ b/assets/js/base/components/quantity-selector/index.tsx
@@ -4,7 +4,7 @@
 import { __, sprintf } from '@wordpress/i18n';
 import { speak } from '@wordpress/a11y';
 import classNames from 'classnames';
-import { useCallback } from '@wordpress/element';
+import { useCallback, useLayoutEffect } from '@wordpress/element';
 import { DOWN, UP } from '@wordpress/keycodes';
 import { useDebouncedCallback } from 'use-debounce';
 
@@ -74,13 +74,8 @@ const QuantitySelector = ( {
 	/**
 	 * The goal of this function is to normalize what was inserted,
 	 * but after the customer has stopped typing.
-	 *
-	 * It's important to wait before normalizing or we end up with
-	 * a frustrating experience, for example, if the minimum is 2 and
-	 * the customer is trying to type "10", premature normalizing would
-	 * always kick in at "1" and turn that into 2.
 	 */
-	const normalizeQuantity = useDebouncedCallback(
+	const normalizeQuantity = useCallback(
 		( initialValue: number ) => {
 			// We copy the starting value.
 			let value = initialValue;
@@ -105,10 +100,28 @@ const QuantitySelector = ( {
 				onChange( value );
 			}
 		},
+		[ hasMaximum, maximum, minimum, onChange, step ]
+	);
+
+	/*
+	 * It's important to wait before normalizing or we end up with
+	 * a frustrating experience, for example, if the minimum is 2 and
+	 * the customer is trying to type "10", premature normalizing would
+	 * always kick in at "1" and turn that into 2.
+	 */
+	const debouncedNormalizeQuantity = useDebouncedCallback(
+		normalizeQuantity,
 		// This value is deliberately smaller than what's in useStoreCartItemQuantity so we don't end up with two requests.
 		300
 	);
 
+	/**
+	 * Normalize qty on mount before render.
+	 */
+	useLayoutEffect( () => {
+		normalizeQuantity( quantity );
+	}, [ quantity, normalizeQuantity ] );
+
 	/**
 	 * Handles keyboard up and down keys to change quantity value.
 	 *
@@ -160,7 +173,7 @@ const QuantitySelector = ( {
 						// we commit this value immediately.
 						onChange( value );
 						// but once the customer has stopped typing, we make sure his value is respecting the bounds (maximum value, minimum value, step value), and commit the normalized value.
-						normalizeQuantity( value );
+						debouncedNormalizeQuantity( value );
 					}
 				} }
 				aria-label={ sprintf(

From 27315f95c746f7dc76db339387637e3a6b4d70ae Mon Sep 17 00:00:00 2001
From: Mike Jolley <mike.jolley@me.com>
Date: Tue, 11 Jan 2022 10:54:31 +0000
Subject: [PATCH 17/17] Update docs

---
 bin/hook-docs/data/filters.json | 77 +++++++++++++++------------------
 docs/extensibility/filters.md   | 60 ++++++++-----------------
 2 files changed, 53 insertions(+), 84 deletions(-)

diff --git a/bin/hook-docs/data/filters.json b/bin/hook-docs/data/filters.json
index 379eb2cacdf..178329e58a3 100644
--- a/bin/hook-docs/data/filters.json
+++ b/bin/hook-docs/data/filters.json
@@ -815,94 +815,85 @@
             "args": 1
         },
         {
-            "name": "woocommerce_store_api_item_quantity_minimum",
-            "file": "StoreApi/Schemas/CartItemSchema.php",
+            "name": "woocommerce_store_api_product_quantity_limit",
+            "file": "StoreApi/Utilities/QuantityLimits.php",
             "type": "filter",
             "doc": {
-                "description": "Filters the quantity minimum for a cart item in Store API.",
-                "long_description": "",
+                "description": "Filters the quantity limit for a product being added to the cart via the Store API.",
+                "long_description": "Filters the variation option name for custom option slugs.",
                 "tags": [
                     {
                         "name": "param",
-                        "content": "Cart item array.",
+                        "content": "Quantity limit which defaults to 99 unless sold individually.",
                         "types": [
-                            "array"
+                            "integer"
                         ],
-                        "variable": "$cart_item"
+                        "variable": "$quantity_limit"
                     },
-                    {
-                        "name": "return",
-                        "content": "",
-                        "types": [
-                            "\\Automattic\\WooCommerce\\Blocks\\StoreApi\\Schemas\\number"
-                        ]
-                    }
-                ],
-                "long_description_html": ""
-            }
-        },
-        {
-            "name": "woocommerce_store_api_item_quantity_step",
-            "file": "StoreApi/Schemas/CartItemSchema.php",
-            "type": "filter",
-            "doc": {
-                "description": "Filters the quantity increment for a cart item in Store API.",
-                "long_description": "",
-                "tags": [
                     {
                         "name": "param",
-                        "content": "Cart item array.",
+                        "content": "Product instance.",
                         "types": [
-                            "array"
+                            "\\WC_Product"
                         ],
-                        "variable": "$cart_item"
+                        "variable": "$product"
                     },
                     {
                         "name": "return",
                         "content": "",
                         "types": [
-                            "\\Automattic\\WooCommerce\\Blocks\\StoreApi\\Schemas\\number"
+                            "integer"
                         ]
                     }
                 ],
-                "long_description_html": ""
-            }
+                "long_description_html": "<p>Filters the variation option name for custom option slugs.</p>"
+            },
+            "args": 2
         },
         {
-            "name": "woocommerce_store_api_product_quantity_limit",
-            "file": "StoreApi/Schemas/ProductSchema.php",
+            "name": "woocommerce_store_api_product_quantity_{$value_type}",
+            "file": "StoreApi/Utilities/QuantityLimits.php",
             "type": "filter",
             "doc": {
-                "description": "Filters the quantity limit for a product being added to the cart via the Store API.",
-                "long_description": "Filters the variation option name for custom option slugs.",
+                "description": "Filters the quantity minimum for a cart item in Store API. This allows extensions to control the minimum qty of items already within the cart.",
+                "long_description": "The suffix of the hook will vary depending on the value being filtered. For example, minimum, maximum, multiple_of, editable.",
                 "tags": [
                     {
                         "name": "param",
-                        "content": "Quantity limit which defaults to 99 unless sold individually.",
+                        "content": "The value being filtered.",
                         "types": [
-                            "integer"
+                            "mixed"
                         ],
-                        "variable": "$quantity_limit"
+                        "variable": "$value"
                     },
                     {
                         "name": "param",
-                        "content": "Product instance.",
+                        "content": "The product object.",
                         "types": [
                             "\\WC_Product"
                         ],
                         "variable": "$product"
                     },
+                    {
+                        "name": "param",
+                        "content": "The cart item if the product exists in the cart, or null.",
+                        "types": [
+                            "array",
+                            "null"
+                        ],
+                        "variable": "$cart_item"
+                    },
                     {
                         "name": "return",
                         "content": "",
                         "types": [
-                            "integer"
+                            "mixed"
                         ]
                     }
                 ],
-                "long_description_html": "<p>Filters the variation option name for custom option slugs.</p>"
+                "long_description_html": "<p>The suffix of the hook will vary depending on the value being filtered. For example, minimum, maximum, multiple_of, editable.</p>"
             },
-            "args": 2
+            "args": 3
         },
         {
             "name": "woocommerce_variation_option_name",
diff --git a/docs/extensibility/filters.md b/docs/extensibility/filters.md
index 7a87746fbcf..db690f3e034 100644
--- a/docs/extensibility/filters.md
+++ b/docs/extensibility/filters.md
@@ -29,9 +29,8 @@
  - [woocommerce_shipping_package_name](#woocommerce_shipping_package_name)
  - [woocommerce_show_page_title](#woocommerce_show_page_title)
  - [woocommerce_store_api_disable_nonce_check](#woocommerce_store_api_disable_nonce_check)
- - [woocommerce_store_api_item_quantity_minimum](#woocommerce_store_api_item_quantity_minimum)
- - [woocommerce_store_api_item_quantity_step](#woocommerce_store_api_item_quantity_step)
  - [woocommerce_store_api_product_quantity_limit](#woocommerce_store_api_product_quantity_limit)
+ - [woocommerce_store_api_product_quantity_{$value_type}](#woocommerce_store_api_product_quantity_-value_type)
  - [woocommerce_variation_option_name](#woocommerce_variation_option_name)
 
 ---
@@ -694,89 +693,68 @@ apply_filters( 'woocommerce_store_api_disable_nonce_check', boolean $disable_non
 
 ---
 
-## woocommerce_store_api_item_quantity_minimum
+## woocommerce_store_api_product_quantity_limit
 
 
-Filters the quantity minimum for a cart item in Store API.
+Filters the quantity limit for a product being added to the cart via the Store API.
 
 ```php
-apply_filters( 'woocommerce_store_api_item_quantity_minimum', array $cart_item )
+apply_filters( 'woocommerce_store_api_product_quantity_limit', integer $quantity_limit, \WC_Product $product )
 ```
 
-### Parameters
-
-| Argument | Type | Description |
-| -------- | ---- | ----------- |
-| $cart_item | array | Cart item array. |
-
-### Returns
-
-
-`\Automattic\WooCommerce\Blocks\StoreApi\Schemas\number` 
-
-### Source
-
-
-File: [StoreApi/Schemas/CartItemSchema.php](../src/StoreApi/Schemas/CartItemSchema.php)
-
----
-
-## woocommerce_store_api_item_quantity_step
-
-
-Filters the quantity increment for a cart item in Store API.
+### Description
 
-```php
-apply_filters( 'woocommerce_store_api_item_quantity_step', array $cart_item )
-```
+<p>Filters the variation option name for custom option slugs.</p>
 
 ### Parameters
 
 | Argument | Type | Description |
 | -------- | ---- | ----------- |
-| $cart_item | array | Cart item array. |
+| $quantity_limit | integer | Quantity limit which defaults to 99 unless sold individually. |
+| $product | \WC_Product | Product instance. |
 
 ### Returns
 
 
-`\Automattic\WooCommerce\Blocks\StoreApi\Schemas\number` 
+`integer` 
 
 ### Source
 
 
-File: [StoreApi/Schemas/CartItemSchema.php](../src/StoreApi/Schemas/CartItemSchema.php)
+ - [StoreApi/Utilities/QuantityLimits.php](../src/StoreApi/Utilities/QuantityLimits.php)
 
 ---
 
-## woocommerce_store_api_product_quantity_limit
+## woocommerce_store_api_product_quantity_{$value_type}
 
 
-Filters the quantity limit for a product being added to the cart via the Store API.
+Filters the quantity minimum for a cart item in Store API. This allows extensions to control the minimum qty of items already within the cart.
 
 ```php
-apply_filters( 'woocommerce_store_api_product_quantity_limit', integer $quantity_limit, \WC_Product $product )
+apply_filters( 'woocommerce_store_api_product_quantity_{$value_type}', mixed $value, \WC_Product $product, array|null $cart_item )
 ```
 
 ### Description
 
-<p>Filters the variation option name for custom option slugs.</p>
+<p>The suffix of the hook will vary depending on the value being filtered. For example, minimum, maximum, multiple_of, editable.</p>
 
 ### Parameters
 
 | Argument | Type | Description |
 | -------- | ---- | ----------- |
-| $quantity_limit | integer | Quantity limit which defaults to 99 unless sold individually. |
-| $product | \WC_Product | Product instance. |
+| $value | mixed | The value being filtered. |
+| $product | \WC_Product | The product object. |
+| $cart_item | array, null | The cart item if the product exists in the cart, or null. |
 
 ### Returns
 
 
-`integer` 
+`mixed` 
 
 ### Source
 
 
- - [StoreApi/Schemas/ProductSchema.php](../src/StoreApi/Schemas/ProductSchema.php)
+ - [StoreApi/Utilities/QuantityLimits.php](../src/StoreApi/Utilities/QuantityLimits.php)
 
 ---