From 88f599c20a6e353f3f798331a97208b443709baf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9?= <583546+oandregal@users.noreply.github.com>
Date: Fri, 18 Oct 2024 13:07:11 +0200
Subject: [PATCH 01/13] Remove hotfix

---
 packages/block-editor/src/store/selectors.js | 14 ++------------
 1 file changed, 2 insertions(+), 12 deletions(-)

diff --git a/packages/block-editor/src/store/selectors.js b/packages/block-editor/src/store/selectors.js
index 787225f18a0a57..b5afb2891ef1cf 100644
--- a/packages/block-editor/src/store/selectors.js
+++ b/packages/block-editor/src/store/selectors.js
@@ -1628,18 +1628,8 @@ const isBlockVisibleInTheInserter = (
 	checkedBlocks.add( blockName );
 
 	// If parent blocks are not visible, child blocks should be hidden too.
-	//
-	// In some scenarios, blockType.parent may be a string.
-	// A better approach would be sanitize parent in all the places that can be modified:
-	// block registration, processBlockType, filters, etc.
-	// In the meantime, this is a hotfix to prevent the editor from crashing.
-	const parent =
-		typeof blockType.parent === 'string' ||
-		blockType.parent instanceof String
-			? [ blockType.parent ]
-			: blockType.parent;
-	if ( Array.isArray( parent ) ) {
-		return parent.some(
+	if ( Array.isArray( blockType.parent ) ) {
+		return blockType.parent.some(
 			( name ) =>
 				( blockName !== name &&
 					isBlockVisibleInTheInserter(

From ad17f4a7ef66e532eff9d10c0c59dbcb363df743 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9?= <583546+oandregal@users.noreply.github.com>
Date: Fri, 18 Oct 2024 17:52:26 +0200
Subject: [PATCH 02/13] Convert parent to array in block registration

---
 packages/blocks/src/api/registration.js | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/packages/blocks/src/api/registration.js b/packages/blocks/src/api/registration.js
index ef1b6bd20a4cdd..429a7235cded48 100644
--- a/packages/blocks/src/api/registration.js
+++ b/packages/blocks/src/api/registration.js
@@ -232,6 +232,13 @@ export function registerBlockType( blockNameOrMetadata, settings ) {
 		return;
 	}
 
+	if (
+		typeof settings?.parent === 'string' ||
+		settings?.parent instanceof String
+	) {
+		settings.parent = [ settings.parent ];
+	}
+
 	if ( 1 === settings?.parent?.length && name === settings.parent[ 0 ] ) {
 		warning(
 			'Block "' +

From c9a842b23c663d84487f7e1e3ee7bdbdf19d7162 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9?= <583546+oandregal@users.noreply.github.com>
Date: Fri, 18 Oct 2024 17:52:40 +0200
Subject: [PATCH 03/13] Convert parent to array in block processing

---
 packages/blocks/src/store/process-block-type.js | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/packages/blocks/src/store/process-block-type.js b/packages/blocks/src/store/process-block-type.js
index ae8f92f84cfabb..dfc8e47ac051d4 100644
--- a/packages/blocks/src/store/process-block-type.js
+++ b/packages/blocks/src/store/process-block-type.js
@@ -197,5 +197,12 @@ export const processBlockType =
 			return;
 		}
 
+		if (
+			typeof settings.parent === 'string' ||
+			settings.parent instanceof String
+		) {
+			settings.parent = [ settings.parent ];
+		}
+
 		return settings;
 	};

From d73432c68261044abb6c1ce18eedec846f93d7ac Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9?= <583546+oandregal@users.noreply.github.com>
Date: Mon, 21 Oct 2024 12:33:21 +0200
Subject: [PATCH 04/13] Test parent is array after having registered as a
 string

---
 packages/blocks/src/api/test/registration.js | 27 ++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/packages/blocks/src/api/test/registration.js b/packages/blocks/src/api/test/registration.js
index 656e9471a541b8..7db5cc7a65c8a6 100644
--- a/packages/blocks/src/api/test/registration.js
+++ b/packages/blocks/src/api/test/registration.js
@@ -742,6 +742,33 @@ describe( 'blocks', () => {
 			} );
 		} );
 
+		it( 'should transform parent string to array', () => {
+			const blockType = {
+				save: noop,
+				category: 'text',
+				title: 'block title',
+				parent: 'core/paragraph',
+			};
+			registerBlockType( 'core/test-block-parent-string', blockType );
+			expect( getBlockType( 'core/test-block-parent-string' ) ).toEqual( {
+				name: 'core/test-block-parent-string',
+				save: noop,
+				category: 'text',
+				title: 'block title',
+				icon: { src: BLOCK_ICON_DEFAULT },
+				attributes: {},
+				providesContext: {},
+				usesContext: [],
+				keywords: [],
+				selectors: {},
+				supports: {},
+				styles: [],
+				variations: [],
+				blockHooks: {},
+				parent: [ 'core/paragraph' ],
+			} );
+		} );
+
 		describe( 'applyFilters', () => {
 			afterEach( () => {
 				removeAllFilters( 'blocks.registerBlockType' );

From 098d5dcd379795bfc5974dd27d006a1b93069847 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9?= <583546+oandregal@users.noreply.github.com>
Date: Mon, 21 Oct 2024 17:26:16 +0200
Subject: [PATCH 05/13] Enforce parent being an array if it is present

---
 packages/blocks/src/api/registration.js         | 11 +++++++++++
 packages/blocks/src/store/process-block-type.js | 11 +++++++++++
 2 files changed, 22 insertions(+)

diff --git a/packages/blocks/src/api/registration.js b/packages/blocks/src/api/registration.js
index 429a7235cded48..ef7a2d464b503c 100644
--- a/packages/blocks/src/api/registration.js
+++ b/packages/blocks/src/api/registration.js
@@ -232,6 +232,9 @@ export function registerBlockType( blockNameOrMetadata, settings ) {
 		return;
 	}
 
+	// Parent being an array hasn't been enforced in the past,
+	// so this is a way to maintain backwards compatibility
+	// with 3rd party blocks that may have been using it as a string.
 	if (
 		typeof settings?.parent === 'string' ||
 		settings?.parent instanceof String
@@ -239,6 +242,14 @@ export function registerBlockType( blockNameOrMetadata, settings ) {
 		settings.parent = [ settings.parent ];
 	}
 
+	if ( ! Array.isArray( settings?.parent ) && 'parent' in settings ) {
+		warning(
+			'Block parent must be an array of block types, but it is ',
+			settings.parent
+		);
+		return;
+	}
+
 	if ( 1 === settings?.parent?.length && name === settings.parent[ 0 ] ) {
 		warning(
 			'Block "' +
diff --git a/packages/blocks/src/store/process-block-type.js b/packages/blocks/src/store/process-block-type.js
index dfc8e47ac051d4..030ce594496074 100644
--- a/packages/blocks/src/store/process-block-type.js
+++ b/packages/blocks/src/store/process-block-type.js
@@ -197,6 +197,9 @@ export const processBlockType =
 			return;
 		}
 
+		// Parent being an array hasn't been enforced in the past,
+		// so this is a way to maintain backwards compatibility
+		// with 3rd party blocks that may have been using it as a string.
 		if (
 			typeof settings.parent === 'string' ||
 			settings.parent instanceof String
@@ -204,5 +207,13 @@ export const processBlockType =
 			settings.parent = [ settings.parent ];
 		}
 
+		if ( ! Array.isArray( settings?.parent ) && 'parent' in settings ) {
+			warning(
+				'Block parent must be an array of block types, but it is ',
+				settings?.parent
+			);
+			return;
+		}
+
 		return settings;
 	};

From 3ec812c3d1858c0aa39a71b3907e229306e512a7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9?= <583546+oandregal@users.noreply.github.com>
Date: Mon, 21 Oct 2024 17:33:19 +0200
Subject: [PATCH 06/13] Prevent against setting being undefined

---
 packages/blocks/src/api/registration.js         | 5 ++++-
 packages/blocks/src/store/process-block-type.js | 5 ++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/packages/blocks/src/api/registration.js b/packages/blocks/src/api/registration.js
index ef7a2d464b503c..cd0c95c59fab83 100644
--- a/packages/blocks/src/api/registration.js
+++ b/packages/blocks/src/api/registration.js
@@ -242,7 +242,10 @@ export function registerBlockType( blockNameOrMetadata, settings ) {
 		settings.parent = [ settings.parent ];
 	}
 
-	if ( ! Array.isArray( settings?.parent ) && 'parent' in settings ) {
+	if (
+		! Array.isArray( settings?.parent ) &&
+		settings?.parent !== undefined
+	) {
 		warning(
 			'Block parent must be an array of block types, but it is ',
 			settings.parent
diff --git a/packages/blocks/src/store/process-block-type.js b/packages/blocks/src/store/process-block-type.js
index 030ce594496074..95dcc86f20bc58 100644
--- a/packages/blocks/src/store/process-block-type.js
+++ b/packages/blocks/src/store/process-block-type.js
@@ -207,7 +207,10 @@ export const processBlockType =
 			settings.parent = [ settings.parent ];
 		}
 
-		if ( ! Array.isArray( settings?.parent ) && 'parent' in settings ) {
+		if (
+			! Array.isArray( settings?.parent ) &&
+			settings?.parent !== undefined
+		) {
 			warning(
 				'Block parent must be an array of block types, but it is ',
 				settings?.parent

From 0db777fe7c9e439f9ee984802aab1db63fb49ea1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9?= <583546+oandregal@users.noreply.github.com>
Date: Mon, 21 Oct 2024 17:37:35 +0200
Subject: [PATCH 07/13] Raises warning if parent is string and document in
 CHANGELOG

---
 packages/blocks/CHANGELOG.md                    | 2 ++
 packages/blocks/src/api/registration.js         | 3 +++
 packages/blocks/src/store/process-block-type.js | 3 +++
 3 files changed, 8 insertions(+)

diff --git a/packages/blocks/CHANGELOG.md b/packages/blocks/CHANGELOG.md
index 73a700428674b2..706b86f20dc200 100644
--- a/packages/blocks/CHANGELOG.md
+++ b/packages/blocks/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- Enforce `blockType.parent` to be an array. While `parent` being a string wasn't never supported, it worked with some unintended side-effects that have been fixed by [#66250](https://github.com/WordPress/gutenberg/pull/66250). For that reason, we've added some code that automatically migrates strings to arrays — though it still raises a warning.
+
 ## 13.10.0 (2024-10-16)
 
 ## 13.9.0 (2024-10-03)
diff --git a/packages/blocks/src/api/registration.js b/packages/blocks/src/api/registration.js
index cd0c95c59fab83..85a3f2a213cd59 100644
--- a/packages/blocks/src/api/registration.js
+++ b/packages/blocks/src/api/registration.js
@@ -240,6 +240,9 @@ export function registerBlockType( blockNameOrMetadata, settings ) {
 		settings?.parent instanceof String
 	) {
 		settings.parent = [ settings.parent ];
+		warning(
+			'Block parent must be an array of block types, but it is a string'
+		);
 	}
 
 	if (
diff --git a/packages/blocks/src/store/process-block-type.js b/packages/blocks/src/store/process-block-type.js
index 95dcc86f20bc58..29ff031c6d1c10 100644
--- a/packages/blocks/src/store/process-block-type.js
+++ b/packages/blocks/src/store/process-block-type.js
@@ -205,6 +205,9 @@ export const processBlockType =
 			settings.parent instanceof String
 		) {
 			settings.parent = [ settings.parent ];
+			warning(
+				'Block parent must be an array of block types, but it is a string'
+			);
 		}
 
 		if (

From 6248fd0738e0bdd9f26880e5862f3f92adab47a3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9?= <583546+oandregal@users.noreply.github.com>
Date: Mon, 21 Oct 2024 17:47:56 +0200
Subject: [PATCH 08/13] Remove warning

---
 packages/blocks/src/api/registration.js         | 3 ---
 packages/blocks/src/store/process-block-type.js | 3 ---
 2 files changed, 6 deletions(-)

diff --git a/packages/blocks/src/api/registration.js b/packages/blocks/src/api/registration.js
index 85a3f2a213cd59..cd0c95c59fab83 100644
--- a/packages/blocks/src/api/registration.js
+++ b/packages/blocks/src/api/registration.js
@@ -240,9 +240,6 @@ export function registerBlockType( blockNameOrMetadata, settings ) {
 		settings?.parent instanceof String
 	) {
 		settings.parent = [ settings.parent ];
-		warning(
-			'Block parent must be an array of block types, but it is a string'
-		);
 	}
 
 	if (
diff --git a/packages/blocks/src/store/process-block-type.js b/packages/blocks/src/store/process-block-type.js
index 29ff031c6d1c10..95dcc86f20bc58 100644
--- a/packages/blocks/src/store/process-block-type.js
+++ b/packages/blocks/src/store/process-block-type.js
@@ -205,9 +205,6 @@ export const processBlockType =
 			settings.parent instanceof String
 		) {
 			settings.parent = [ settings.parent ];
-			warning(
-				'Block parent must be an array of block types, but it is a string'
-			);
 		}
 
 		if (

From d9a16db65a030f5d95f9cdcf3036f66fab7e484f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9?= <583546+oandregal@users.noreply.github.com>
Date: Tue, 22 Oct 2024 08:34:58 +0200
Subject: [PATCH 09/13] Add Bug fixes heading

---
 packages/blocks/CHANGELOG.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/packages/blocks/CHANGELOG.md b/packages/blocks/CHANGELOG.md
index 706b86f20dc200..1404a6fe1e3e20 100644
--- a/packages/blocks/CHANGELOG.md
+++ b/packages/blocks/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+### Bug fixes
+
 - Enforce `blockType.parent` to be an array. While `parent` being a string wasn't never supported, it worked with some unintended side-effects that have been fixed by [#66250](https://github.com/WordPress/gutenberg/pull/66250). For that reason, we've added some code that automatically migrates strings to arrays — though it still raises a warning.
 
 ## 13.10.0 (2024-10-16)

From 002ac7cec3337f5f5d56c9f154a3e337b890f3c4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9?= <583546+oandregal@users.noreply.github.com>
Date: Tue, 22 Oct 2024 13:05:15 +0200
Subject: [PATCH 10/13] Move validation to processBlockType

---
 packages/blocks/src/api/registration.js       | 30 -------------------
 .../blocks/src/store/process-block-type.js    | 17 ++++++++---
 2 files changed, 13 insertions(+), 34 deletions(-)

diff --git a/packages/blocks/src/api/registration.js b/packages/blocks/src/api/registration.js
index cd0c95c59fab83..2f4bab2b5f2589 100644
--- a/packages/blocks/src/api/registration.js
+++ b/packages/blocks/src/api/registration.js
@@ -232,36 +232,6 @@ export function registerBlockType( blockNameOrMetadata, settings ) {
 		return;
 	}
 
-	// Parent being an array hasn't been enforced in the past,
-	// so this is a way to maintain backwards compatibility
-	// with 3rd party blocks that may have been using it as a string.
-	if (
-		typeof settings?.parent === 'string' ||
-		settings?.parent instanceof String
-	) {
-		settings.parent = [ settings.parent ];
-	}
-
-	if (
-		! Array.isArray( settings?.parent ) &&
-		settings?.parent !== undefined
-	) {
-		warning(
-			'Block parent must be an array of block types, but it is ',
-			settings.parent
-		);
-		return;
-	}
-
-	if ( 1 === settings?.parent?.length && name === settings.parent[ 0 ] ) {
-		warning(
-			'Block "' +
-				name +
-				'" cannot be a parent of itself. Please remove the block name from the parent list.'
-		);
-		return;
-	}
-
 	if ( ! /^[a-z][a-z0-9-]*\/[a-z][a-z0-9-]*$/.test( name ) ) {
 		warning(
 			'Block names must contain a namespace prefix, include only lowercase alphanumeric characters or dashes, and start with a letter. Example: my-plugin/my-custom-block'
diff --git a/packages/blocks/src/store/process-block-type.js b/packages/blocks/src/store/process-block-type.js
index 95dcc86f20bc58..63bef081a6b5dc 100644
--- a/packages/blocks/src/store/process-block-type.js
+++ b/packages/blocks/src/store/process-block-type.js
@@ -201,8 +201,8 @@ export const processBlockType =
 		// so this is a way to maintain backwards compatibility
 		// with 3rd party blocks that may have been using it as a string.
 		if (
-			typeof settings.parent === 'string' ||
-			settings.parent instanceof String
+			typeof settings?.parent === 'string' ||
+			settings?.parent instanceof String
 		) {
 			settings.parent = [ settings.parent ];
 		}
@@ -212,8 +212,17 @@ export const processBlockType =
 			settings?.parent !== undefined
 		) {
 			warning(
-				'Block parent must be an array of block types, but it is ',
-				settings?.parent
+				'Block parent must be undefined or an array of block types, but it is ',
+				settings.parent
+			);
+			return;
+		}
+
+		if ( 1 === settings?.parent?.length && name === settings.parent[ 0 ] ) {
+			warning(
+				'Block "' +
+					name +
+					'" cannot be a parent of itself. Please remove the block name from the parent list.'
 			);
 			return;
 		}

From f35fb12525adc54d8ae54cd0da8e66901bf539de Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9?= <583546+oandregal@users.noreply.github.com>
Date: Tue, 22 Oct 2024 13:16:04 +0200
Subject: [PATCH 11/13] Update changelog

---
 packages/blocks/CHANGELOG.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/blocks/CHANGELOG.md b/packages/blocks/CHANGELOG.md
index 1404a6fe1e3e20..c8225d811031a6 100644
--- a/packages/blocks/CHANGELOG.md
+++ b/packages/blocks/CHANGELOG.md
@@ -4,7 +4,7 @@
 
 ### Bug fixes
 
-- Enforce `blockType.parent` to be an array. While `parent` being a string wasn't never supported, it worked with some unintended side-effects that have been fixed by [#66250](https://github.com/WordPress/gutenberg/pull/66250). For that reason, we've added some code that automatically migrates strings to arrays — though it still raises a warning.
+- Normalize `blockType.parent` to be an array. While string values were never supported, they appeared to work with some unintended side-effects that have been fixed by [#66250](https://github.com/WordPress/gutenberg/pull/66250). For that reason, we've added some code that automatically migrates strings to arrays — though it still raises a warning.
 
 ## 13.10.0 (2024-10-16)
 

From 4369ec0f999dbd33d599a0d5d43f01df5a603cf8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9?= <583546+oandregal@users.noreply.github.com>
Date: Tue, 22 Oct 2024 13:26:21 +0200
Subject: [PATCH 12/13] Add back test and warning about parent as a string

---
 packages/blocks/src/api/test/registration.js    | 10 ++++++++--
 packages/blocks/src/store/process-block-type.js | 14 ++++++++++----
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/packages/blocks/src/api/test/registration.js b/packages/blocks/src/api/test/registration.js
index 7db5cc7a65c8a6..5941415e61fe55 100644
--- a/packages/blocks/src/api/test/registration.js
+++ b/packages/blocks/src/api/test/registration.js
@@ -749,8 +749,14 @@ describe( 'blocks', () => {
 				title: 'block title',
 				parent: 'core/paragraph',
 			};
-			registerBlockType( 'core/test-block-parent-string', blockType );
-			expect( getBlockType( 'core/test-block-parent-string' ) ).toEqual( {
+			const block = registerBlockType(
+				'core/test-block-parent-string',
+				blockType
+			);
+			expect( console ).toHaveWarnedWith(
+				'Parent must be undefined or an array of strings (block types), but it is a string.'
+			);
+			expect( block ).toEqual( {
 				name: 'core/test-block-parent-string',
 				save: noop,
 				category: 'text',
diff --git a/packages/blocks/src/store/process-block-type.js b/packages/blocks/src/store/process-block-type.js
index 63bef081a6b5dc..bc7b1a0e10e774 100644
--- a/packages/blocks/src/store/process-block-type.js
+++ b/packages/blocks/src/store/process-block-type.js
@@ -197,14 +197,20 @@ export const processBlockType =
 			return;
 		}
 
-		// Parent being an array hasn't been enforced in the past,
-		// so this is a way to maintain backwards compatibility
-		// with 3rd party blocks that may have been using it as a string.
 		if (
 			typeof settings?.parent === 'string' ||
 			settings?.parent instanceof String
 		) {
 			settings.parent = [ settings.parent ];
+			warning(
+				'Parent must be undefined or an array of strings (block types), but it is a string.'
+			);
+			// Intentionally continue:
+			//
+			// While string values were never supported, they appeared to work with some unintended side-effects
+			// that have been fixed by [#66250](https://github.com/WordPress/gutenberg/pull/66250).
+			//
+			// To be backwards-compatible, this code that automatically migrates strings to arrays.
 		}
 
 		if (
@@ -212,7 +218,7 @@ export const processBlockType =
 			settings?.parent !== undefined
 		) {
 			warning(
-				'Block parent must be undefined or an array of block types, but it is ',
+				'Parent must be undefined or an array of block types, but it is ',
 				settings.parent
 			);
 			return;

From 83bfdf98a9a4ad73e7cc720ccc1d8a33d299e9d9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andr=C3=A9?= <583546+oandregal@users.noreply.github.com>
Date: Tue, 22 Oct 2024 16:34:29 +0200
Subject: [PATCH 13/13] Change Bug to BreakingChange

---
 packages/blocks/CHANGELOG.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/blocks/CHANGELOG.md b/packages/blocks/CHANGELOG.md
index c8225d811031a6..eebbe7148e8055 100644
--- a/packages/blocks/CHANGELOG.md
+++ b/packages/blocks/CHANGELOG.md
@@ -2,7 +2,7 @@
 
 ## Unreleased
 
-### Bug fixes
+### Breaking changes
 
 - Normalize `blockType.parent` to be an array. While string values were never supported, they appeared to work with some unintended side-effects that have been fixed by [#66250](https://github.com/WordPress/gutenberg/pull/66250). For that reason, we've added some code that automatically migrates strings to arrays — though it still raises a warning.