Add allowedBlocks field to block.json to specify allowed children

docs/how-to-guides/block-tutorial/nested-blocks-inner-blocks.md

@@ -38,14 +38,16 @@ registerBlockType( 'gutenberg-examples/example-06', {
 
 ## Allowed blocks
 
-Using the `allowedBlocks` property, you can define the set of blocks allowed in your InnerBlock. This restricts the blocks that can be included only to those listed, all other blocks will not show in the inserter.
+Using the `allowedBlocks` prop, you can further limit, in addition to the `allowedBlocks` field in `block.json`, which blocks can be inserted as direct descendants of this block. It is useful to determine the list of allowed blocks dynamically, individually for each block. For example, determined by a block attribute:
 
 ```js
-const ALLOWED_BLOCKS = [ 'core/image', 'core/paragraph' ];
+const { allowedBlocks } = attributes;
 //...
-<InnerBlocks allowedBlocks={ ALLOWED_BLOCKS } />;
+<InnerBlocks allowedBlocks={ allowedBlocks } />;
 ```
 
+If the list of allowed blocks is always the same, prefer the [`allowedBlocks` block setting](#defining-a-children-block-relationship) instead.
+
 ## Orientation
 
 By default, `InnerBlocks` expects its blocks to be shown in a vertical list. A valid use-case is to style inner blocks to appear horizontally, for instance by adding CSS flex or grid properties to the inner blocks wrapper. When blocks are styled in such a way, the `orientation` prop can be set to indicate that a horizontal layout is being used:
@@ -109,12 +111,13 @@ add_action( 'init', function() {
 } );
 ```
 
-## Using parent and ancestor relationships in blocks
+## Using parent, ancestor and children relationships in blocks
 
-A common pattern for using InnerBlocks is to create a custom block that will be only be available if its parent block is inserted. This allows builders to establish a relationship between blocks, while limiting a nested block's discoverability. Currently, there are two relationships builders can use: `parent` and `ancestor`. The differences are:
+A common pattern for using InnerBlocks is to create a custom block that will be only be available if its parent block is inserted. This allows builders to establish a relationship between blocks, while limiting a nested block's discoverability. There are three relationships that builders can use: `parent`, `ancestor` and `allowedBlocks`. The differences are:
 
 - If you assign a `parent` then you’re stating that the nested block can only be used and inserted as a __direct descendant of the parent__.
 - If you assign an `ancestor` then you’re stating that the nested block can only be used and inserted as a __descendent of the parent__.
+- If you assign the `allowedBlocks` then you’re stating a relationship in the opposite direction, i.e., which blocks can be used and inserted as __direct descendants of this block__.
 
 The key difference between `parent` and `ancestor` is `parent` has finer specificity, while an `ancestor` has greater flexibility in its nested hierarchy.
 
@@ -150,6 +153,23 @@ When defining a descendent block, use the `ancestor` block setting. This prevent
 }
 ```
 
+### Defining a children block relationship
+
+An example of this is the Navigation block, which is assigned the `allowedBlocks` block setting. This makes only a certain subset of block types to be available as direct descendants of the Navigation block. See [Navigation code for reference](https://github.com/WordPress/gutenberg/tree/HEAD/packages/block-library/src/navigation).
+
+The `allowedBlocks` setting can be extended by builders of custom blocks. The custom block can hook into the `blocks.registerBlockType` filter and add itself to the available children of the Navigation.
+
+When defining a set of possible descendant blocks, use the `allowedBlocks` block setting. This limits what blocks are showing in the inserter when inserting a new child block.
+
+```json
+{
+	"title": "Navigation",
+	"name": "core/navigation",
+	"allowedBlocks": [ "core/navigation-link", "core/search", "core/social-links", "core/page-list", "core/spacer" ],
+	// ...
+}
+```
+
 ## Using a React hook
 
 You can use a react hook called `useInnerBlocksProps` instead of the `InnerBlocks` component. This hook allows you to take more control over the markup of inner blocks areas.

docs/reference-guides/block-api/block-metadata.md

@@ -186,6 +186,20 @@ Setting `parent` lets a block require that it is only available when nested with
 
 The `ancestor` property makes a block available inside the specified block types at any position of the ancestor block subtree. That allows, for example, to place a ‘Comment Content’ block inside a ‘Column’ block, as long as ‘Column’ is somewhere within a ‘Comment Template’ block. In comparison to the `parent` property blocks that specify their `ancestor` can be placed anywhere in the subtree whilst blocks with a specified `parent` need to be direct children.
 
+### Allowed Blocks
+
+-   Type: `string[]`
+-   Optional
+-   Localized: No
+-   Property: `allowedBlocks`
+-   Since: `WordPress 6.5.0`
+
+```json
+{ "allowedBlocks": [ "my-block/product" ] }
+```
+
+The `allowedBlocks` specifies which block types can be the direct children of the block. For example, a ‘List’ block can allow only ‘List Item’ blocks as children.
+
 ### Icon
 
 -   Type: `string`

docs/reference-guides/block-api/block-registration.md

@@ -275,7 +275,19 @@ The `ancestor` property makes a block available inside the specified block types
 ancestor: [ 'core/columns' ],
 ```
 
-#### Block Hooks (optional)
+#### allowedBlocks (optional)
+
+-   **Type:** `Array`
+-   **Since**: `WordPress 6.5.0`
+
+Setting the `allowedBlocks` property will limit which block types can be nested as direct children of the block.
+
+```js
+// Only allow the Columns block to be nested as direct child of this block
+allowedBlocks: [ 'core/columns' ],
+```
+
+#### blockHooks (optional)
 
 -   **Type:** `Object`
 -   **Since**: `WordPress 6.4.0`

lib/compat/wordpress-6.4/block-hooks.php

@@ -73,6 +73,7 @@ function gutenberg_add_hooked_blocks( $settings, $metadata ) {
 		'keywords'         => 'keywords',
 		'example'          => 'example',
 		'variations'       => 'variations',
+		'allowed_blocks'   => 'allowedBlocks',
 	);
 	// Add `block_hooks` to the list of fields to pick.
 	$fields_to_pick['block_hooks'] = 'blockHooks';

packages/block-editor/src/store/selectors.js

@@ -1563,14 +1563,30 @@ const canInsertBlockTypeUnmemoized = (
 		return false;
 	}
 
-	const parentAllowedBlocks = parentBlockListSettings?.allowedBlocks;
-	const hasParentAllowedBlock = checkAllowList(
-		parentAllowedBlocks,
+	const parentName = getBlockName( state, rootClientId );
+	const parentBlockType = getBlockType( parentName );
+
+	// Look at the `blockType.allowedBlocks` field to determine whether this is an allowed child block.
+	const parentAllowedChildBlocks = parentBlockType?.allowedBlocks;
+	let hasParentAllowedBlock = checkAllowList(
+		parentAllowedChildBlocks,
 		blockName
 	);
 
+	// The `allowedBlocks` block list setting can further limit which blocks are allowed children.
+	if ( hasParentAllowedBlock !== false ) {
+		const parentAllowedBlocks = parentBlockListSettings?.allowedBlocks;
+		const hasParentListAllowedBlock = checkAllowList(
+			parentAllowedBlocks,
+			blockName
+		);
+		// Never downgrade the result from `true` to `null`
+		if ( hasParentListAllowedBlock !== null ) {
+			hasParentAllowedBlock = hasParentListAllowedBlock;
+		}
+	}
+
 	const blockAllowedParentBlocks = blockType.parent;
-	const parentName = getBlockName( state, rootClientId );
 	const hasBlockAllowedParent = checkAllowList(
 		blockAllowedParentBlocks,
 		parentName

packages/block-library/src/buttons/block.json

@@ -4,6 +4,7 @@
 	"name": "core/buttons",
 	"title": "Buttons",
 	"category": "design",
+	"allowedBlocks": [ "core/button" ],
 	"description": "Prompt visitors to take action with a group of button-style links.",
 	"keywords": [ "link" ],
 	"textdomain": "default",

packages/block-library/src/buttons/edit.js

@@ -14,15 +14,8 @@ import {
 import { useSelect } from '@wordpress/data';
 import { store as blocksStore } from '@wordpress/blocks';
 
-/**
- * Internal dependencies
- */
-import { name as buttonBlockName } from '../button';
-
-const ALLOWED_BLOCKS = [ buttonBlockName ];
-
 const DEFAULT_BLOCK = {
-	name: buttonBlockName,
+	name: 'core/button',
 	attributesToCopy: [
 		'backgroundColor',
 		'border',
@@ -48,24 +41,22 @@ function ButtonsEdit( { attributes, className } ) {
 			select( blockEditorStore ).getSettings()
 				.__experimentalPreferredStyleVariations;
 		const buttonVariations = select( blocksStore ).getBlockVariations(
-			buttonBlockName,
+			'core/button',
 			'inserter'
 		);
 		return {
-			preferredStyle:
-				preferredStyleVariations?.value?.[ buttonBlockName ],
+			preferredStyle: preferredStyleVariations?.value?.[ 'core/button' ],
 			hasButtonVariations: buttonVariations.length > 0,
 		};
 	}, [] );
 
 	const innerBlocksProps = useInnerBlocksProps( blockProps, {
-		allowedBlocks: ALLOWED_BLOCKS,
 		defaultBlock: DEFAULT_BLOCK,
 		// This check should be handled by the `Inserter` internally to be consistent across all blocks that use it.
 		directInsert: ! hasButtonVariations,
 		template: [
 			[
-				buttonBlockName,
+				'core/button',
 				{ className: preferredStyle && `is-style-${ preferredStyle }` },
 			],
 		],

packages/block-library/src/buttons/edit.native.js

@@ -21,11 +21,8 @@ import { alignmentHelpers } from '@wordpress/components';
 /**
  * Internal dependencies
  */
-import { name as buttonBlockName } from '../button/';
 import styles from './editor.scss';
 
-const ALLOWED_BLOCKS = [ buttonBlockName ];
-
 const layoutProp = { type: 'default', alignments: [] };
 
 const POPOVER_PROPS = {
@@ -76,7 +73,7 @@ export default function ButtonsEdit( {
 		const preferredStyleVariations =
 			select( blockEditorStore ).getSettings()
 				.__experimentalPreferredStyleVariations;
-		return preferredStyleVariations?.value?.[ buttonBlockName ];
+		return preferredStyleVariations?.value?.[ 'core/button' ];
 	}, [] );
 
 	const { getBlockOrder } = useSelect( blockEditorStore );
@@ -147,10 +144,9 @@ export default function ButtonsEdit( {
 			) }
 			{ resizeObserver }
 			<InnerBlocks
-				allowedBlocks={ ALLOWED_BLOCKS }
 				template={ [
 					[
-						buttonBlockName,
+						'core/button',
 						{
 							className:
 								preferredStyle &&

packages/block-library/src/columns/block.json

@@ -4,6 +4,7 @@
 	"name": "core/columns",
 	"title": "Columns",
 	"category": "design",
+	"allowedBlocks": [ "core/column" ],
 	"description": "Display content in multiple columns, with blocks added to each column.",
 	"textdomain": "default",
 	"attributes": {

packages/block-library/src/columns/edit.js

@@ -40,17 +40,6 @@ import {
 	toWidthPrecision,
 } from './utils';
 
-/**
- * Allowed blocks constant is passed to InnerBlocks precisely as specified here.
- * The contents of the array should never change.
- * The array should contain the name of each block that is allowed.
- * In columns block, the only block we allow is 'core/column'.
- *
- * @constant
- * @type {string[]}
- */
-const ALLOWED_BLOCKS = [ 'core/column' ];
-
 function ColumnsEditContainer( {
 	attributes,
 	setAttributes,
@@ -103,7 +92,6 @@ function ColumnsEditContainer( {
 		className: classes,
 	} );
 	const innerBlocksProps = useInnerBlocksProps( blockProps, {
-		allowedBlocks: ALLOWED_BLOCKS,
 		orientation: 'horizontal',
 		renderAppender: false,
 		templateLock,

packages/block-library/src/columns/edit.native.js

@@ -59,17 +59,6 @@ import {
 } from './columnCalculations.native';
 import ColumnsPreview from '../column/column-preview';
 
-/**
- * Allowed blocks constant is passed to InnerBlocks precisely as specified here.
- * The contents of the array should never change.
- * The array should contain the name of each block that is allowed.
- * In columns block, the only block we allow is 'core/column'.
- *
- * @constant
- * @type {string[]}
- */
-const ALLOWED_BLOCKS = [ 'core/column' ];
-
 /**
  * Number of columns to assume for template in case the user opts to skip
  * template option selection.
@@ -275,7 +264,6 @@ function ColumnsEditContainer( {
 							columnsInRow > 1 ? 'horizontal' : undefined
 						}
 						horizontal={ columnsInRow > 1 }
-						allowedBlocks={ ALLOWED_BLOCKS }
 						contentResizeMode="stretch"
 						onAddBlock={ onAddBlock }
 						onDeleteBlock={

packages/block-library/src/comments-pagination/block.json

@@ -5,6 +5,11 @@
 	"title": "Comments Pagination",
 	"category": "theme",
 	"parent": [ "core/comments" ],
+	"allowedBlocks": [
+		"core/comments-pagination-previous",
+		"core/comments-pagination-numbers",
+		"core/comments-pagination-next"
+	],
 	"description": "Displays a paginated navigation to next/previous set of comments, when applicable.",
 	"textdomain": "default",
 	"attributes": {

packages/block-library/src/comments-pagination/edit.js

@@ -22,11 +22,6 @@ const TEMPLATE = [
 	[ 'core/comments-pagination-numbers' ],
 	[ 'core/comments-pagination-next' ],
 ];
-const ALLOWED_BLOCKS = [
-	'core/comments-pagination-previous',
-	'core/comments-pagination-numbers',
-	'core/comments-pagination-next',
-];
 
 export default function QueryPaginationEdit( {
 	attributes: { paginationArrow },
@@ -52,7 +47,6 @@ export default function QueryPaginationEdit( {
 	const blockProps = useBlockProps();
 	const innerBlocksProps = useInnerBlocksProps( blockProps, {
 		template: TEMPLATE,
-		allowedBlocks: ALLOWED_BLOCKS,
 	} );
 
 	// Get the Discussion settings

packages/block-library/src/form-submit-button/block.json

@@ -7,6 +7,7 @@
 	"category": "common",
 	"icon": "button",
 	"ancestor": [ "core/form" ],
+	"allowedBlocks": [ "core/buttons", "core/button" ],
 	"description": "A submission button for forms.",
 	"keywords": [ "submit", "button", "form" ],
 	"textdomain": "default",

packages/block-library/src/form-submit-button/edit.js

@@ -23,7 +23,6 @@ const TEMPLATE = [
 const Edit = () => {
 	const blockProps = useBlockProps();
 	const innerBlocksProps = useInnerBlocksProps( blockProps, {
-		allowedBlocks: TEMPLATE,
 		template: TEMPLATE,
 		templateLock: 'all',
 	} );

packages/block-library/src/form/block.json

@@ -5,6 +5,15 @@
 	"name": "core/form",
 	"title": "Form",
 	"category": "common",
+	"allowedBlocks": [
+		"core/paragraph",
+		"core/heading",
+		"core/form-input",
+		"core/form-submit-button",
+		"core/form-submission-notification",
+		"core/group",
+		"core/columns"
+	],
 	"description": "A form.",
 	"keywords": [ "container", "wrapper", "row", "section" ],
 	"textdomain": "default",

packages/block-library/src/form/edit.js

@@ -20,16 +20,6 @@ import {
 	formSubmissionNotificationError,
 } from './utils.js';
 
-const ALLOWED_BLOCKS = [
-	'core/paragraph',
-	'core/heading',
-	'core/form-input',
-	'core/form-submit-button',
-	'core/form-submission-notification',
-	'core/group',
-	'core/columns',
-];
-
 const TEMPLATE = [
 	formSubmissionNotificationSuccess,
 	formSubmissionNotificationError,
@@ -76,7 +66,6 @@ const Edit = ( { attributes, setAttributes, clientId } ) => {
 	);
 
 	const innerBlocksProps = useInnerBlocksProps( blockProps, {
-		allowedBlocks: ALLOWED_BLOCKS,
 		template: TEMPLATE,
 		renderAppender: hasInnerBlocks
 			? undefined

packages/block-library/src/gallery/block.json

@@ -4,6 +4,7 @@
 	"name": "core/gallery",
 	"title": "Gallery",
 	"category": "media",
+	"allowedBlocks": [ "core/image" ],
 	"description": "Display multiple images in a rich gallery.",
 	"keywords": [ "images", "photos" ],
 	"textdomain": "default",