Hot fix: Reusable blocks: Prevent recursion

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

@@ -29,6 +29,7 @@ import { store as reusableBlocksStore } from '@wordpress/reusable-blocks';
 /**
  * Internal dependencies
  */
+import hasNestedReusableBlocks from './has-nested-reusable-blocks';
 
 export default function ReusableBlockEdit( { attributes: { ref }, clientId } ) {
 	const { isMissing, hasResolved } = useSelect(
@@ -83,6 +84,16 @@ export default function ReusableBlockEdit( { attributes: { ref }, clientId } ) {
 
 	const blockProps = useBlockProps();
 
+	if ( hasNestedReusableBlocks( blocks ) ) {
+		return (
+			<div { ...blockProps }>
+				<Warning>
+					{ __( `Recursion is cool, until it isn't.` ) }
+				</Warning>
+			</div>
+		);
+	}
+
 	if ( isMissing ) {
 		return (
 			<div { ...blockProps }>

packages/block-library/src/block/has-nested-reusable-blocks.js

@@ -0,0 +1,11 @@
+const DISALLOWED_BLOCKS = [ 'core/block', 'core/template-part' ];
+
+export default function hasNestedReusableBlocks( block ) {
+	if ( Array.isArray( block ) ) {
+		return block.some( hasNestedReusableBlocks );
+	}
+	return (
+		DISALLOWED_BLOCKS.includes( block.name ) ||
+		block.innerBlocks.some( hasNestedReusableBlocks )
+	);
+}

packages/block-library/src/block/test/has-nested-reusable-blocks.js

@@ -0,0 +1,61 @@
+/**
+ * Internal dependencies
+ */
+import hasNestedReusableBlocks from '../has-nested-reusable-blocks';
+
+const badSingleBlock = [
+	{
+		name: 'core/block',
+		innerBlocks: [],
+	},
+];
+
+const goodSingleBlock = [
+	{
+		name: 'core/paragraph',
+		innerBlocks: [],
+	},
+];
+
+const badNestedBlocks = [
+	{
+		name: 'core/paragraph',
+		innerBlocks: [],
+	},
+	{
+		name: 'core/group',
+		innerBlocks: [
+			{
+				name: 'core/template-part',
+				innerBlocks: [],
+			},
+		],
+	},
+];
+
+const goodNestedBlocks = [
+	{
+		name: 'core/paragraph',
+		innerBlocks: [],
+	},
+	{
+		name: 'core/group',
+		innerBlocks: [
+			{
+				name: 'core/paragraph',
+				innerBlocks: [],
+			},
+		],
+	},
+];
+
+describe( 'hasNestedReusableBlocks', () => {
+	it( 'handles shallow block sets', () => {
+		expect( hasNestedReusableBlocks( goodSingleBlock ) ).toBe( false );
+		expect( hasNestedReusableBlocks( badSingleBlock ) ).toBe( true );
+	} );
+	it( 'handles nested blocks', () => {
+		expect( hasNestedReusableBlocks( goodNestedBlocks ) ).toBe( false );
+		expect( hasNestedReusableBlocks( badNestedBlocks ) ).toBe( true );
+	} );
+} );