feat(core): OrderItem.unitPrice now _always_ excludes tax

Relates to #467. This change means that storefronts do not need to do any tax calculations and can
reliably list `unitPrice` and `unitPriceWithTax` and know that the actual net/gross prices
are being listed.

BREAKING CHANGE: The `OrderItem.unitPrice` is now _always_ given as the net (without tax) price
of the related ProductVariant. Formerly, it was either the net or gross price, depending on
the `pricesIncludeTax` setting of the Channel. If you have existing Orders where
`unitPriceIncludesTax = true`, you will need to manually update the `unitPrice` value *before*
running any other migrations for this release. The query will look like:

    `UPDATE order_item SET unitPrice = ROUND(unitPrice / ((taxRate + 100) / 100)) WHERE unitPriceIncludesTax = 1`

packages/core/e2e/shipping-method.e2e-spec.ts

@@ -34,7 +34,7 @@ const calculatorWithMetadata = new ShippingCalculator({
     code: 'calculator-with-metadata',
     description: [{ languageCode: LanguageCode.en, value: 'Has metadata' }],
     args: {},
-    calculate: order => {
+    calculate: () => {
         return {
             price: 100,
             priceWithTax: 100,

packages/core/src/api/schema/type/order.type.graphql

@@ -64,7 +64,7 @@ type OrderItem implements Node {
     cancelled: Boolean!
     unitPrice: Int!
     unitPriceWithTax: Int!
-    unitPriceIncludesTax: Boolean!
+    unitPriceIncludesTax: Boolean! @deprecated(reason: "`unitPrice` is now always without tax")
     taxRate: Float!
     adjustments: [Adjustment!]!
     fulfillment: Fulfillment

packages/core/src/common/finite-state-machine/validate-transition-definition.spec.ts

@@ -46,7 +46,7 @@ describe('FSM validateTransitionDefinition()', () => {
             },
         };
 
-        const result = validateTransitionDefinition(orderStateTransitions, 'AddingItems');
+        const result = validateTransitionDefinition(orderStateTransitions, 'Created');
 
         expect(result.valid).toBe(true);
     });

packages/core/src/entity/order-item/order-item.entity.ts

@@ -1,6 +1,6 @@
 import { Adjustment, AdjustmentType } from '@vendure/common/lib/generated-types';
 import { DeepPartial, ID } from '@vendure/common/lib/shared-types';
-import { Column, Entity, ManyToOne, OneToOne, RelationId } from 'typeorm';
+import { Column, Entity, ManyToOne, OneToOne } from 'typeorm';
 
 import { Calculated } from '../../common/calculated-decorator';
 import { VendureEntity } from '../base/base.entity';
@@ -28,7 +28,11 @@ export class OrderItem extends VendureEntity {
 
     @Column() readonly unitPrice: number;
 
-    @Column() unitPriceIncludesTax: boolean;
+    /**
+     * @deprecated
+     * TODO: remove once the field has been removed from the GraphQL type
+     */
+    unitPriceIncludesTax = false;
 
     @Column({ type: 'decimal', precision: 5, scale: 2, transformer: new DecimalTransformer() })
     taxRate: number;
@@ -55,11 +59,7 @@ export class OrderItem extends VendureEntity {
 
     @Calculated()
     get unitPriceWithTax(): number {
-        if (this.unitPriceIncludesTax) {
-            return this.unitPrice;
-        } else {
-            return Math.round(this.unitPrice * ((100 + this.taxRate) / 100));
-        }
+        return Math.round(this.unitPrice * ((100 + this.taxRate) / 100));
     }
 
     /**
@@ -70,44 +70,30 @@ export class OrderItem extends VendureEntity {
         if (!this.pendingAdjustments) {
             return [];
         }
-        if (this.unitPriceIncludesTax) {
-            return this.pendingAdjustments;
-        } else {
-            return this.pendingAdjustments.map(a => {
-                if (a.type === AdjustmentType.PROMOTION) {
-                    // Add the tax that would have been payable on the discount so that the numbers add up
-                    // for the end-user.
-                    const adjustmentWithTax = Math.round(a.amount * ((100 + this.taxRate) / 100));
-                    return {
-                        ...a,
-                        amount: adjustmentWithTax,
-                    };
-                }
-                return a;
-            });
-        }
+        return this.pendingAdjustments.map(a => {
+            if (a.type === AdjustmentType.PROMOTION) {
+                // Add the tax that would have been payable on the discount so that the numbers add up
+                // for the end-user.
+                const adjustmentWithTax = Math.round(a.amount * ((100 + this.taxRate) / 100));
+                return {
+                    ...a,
+                    amount: adjustmentWithTax,
+                };
+            }
+            return a;
+        });
     }
 
     /**
      * This is the actual, final price of the OrderItem payable by the customer.
      */
     get unitPriceWithPromotionsAndTax(): number {
-        if (this.unitPriceIncludesTax) {
-            return this.unitPriceWithPromotions;
-        } else {
-            return this.unitPriceWithPromotions + this.unitTax;
-        }
+        return this.unitPriceWithPromotions + this.unitTax;
     }
 
     get unitTax(): number {
-        if (this.unitPriceIncludesTax) {
-            return Math.round(
-                this.unitPriceWithPromotions - this.unitPriceWithPromotions / ((100 + this.taxRate) / 100),
-            );
-        } else {
-            const taxAdjustment = this.adjustments.find(a => a.type === AdjustmentType.TAX);
-            return taxAdjustment ? taxAdjustment.amount : 0;
-        }
+        const taxAdjustment = this.adjustments.find(a => a.type === AdjustmentType.TAX);
+        return taxAdjustment ? taxAdjustment.amount : 0;
     }
 
     get promotionAdjustmentsTotal(): number {

packages/core/src/entity/order-line/order-line.entity.ts

@@ -78,24 +78,6 @@ export class OrderLine extends VendureEntity implements HasCustomFields {
         return (this.items || []).filter(i => !i.cancelled);
     }
 
-    /**
-     * Sets whether the unitPrice of each OrderItem in the line includes tax.
-     */
-    setUnitPriceIncludesTax(includesTax: boolean) {
-        this.activeItems.forEach(item => {
-            item.unitPriceIncludesTax = includesTax;
-        });
-    }
-
-    /**
-     * Sets the tax rate being applied to each Orderitem in this line.
-     */
-    setTaxRate(taxRate: number) {
-        this.activeItems.forEach(item => {
-            item.taxRate = taxRate;
-        });
-    }
-
     /**
      * Clears Adjustments from all OrderItems of the given type. If no type
      * is specified, then all adjustments are removed.