Use a patch format and support linkTarget of core/button for Pattern Overrides

lib/experimental/block-bindings/sources/pattern.php

@@ -9,8 +9,23 @@
 		if ( ! _wp_array_get( $block_instance->attributes, array( 'metadata', 'id' ), false ) ) {
 			return null;
 		}
-		$block_id = $block_instance->attributes['metadata']['id'];
-		return _wp_array_get( $block_instance->context, array( 'pattern/overrides', $block_id, $attribute_name ), null );
+		$block_id           = $block_instance->attributes['metadata']['id'];
+		$attribute_override = _wp_array_get( $block_instance->context, array( 'pattern/overrides', $block_id, $attribute_name ), null );
+		if ( null === $attribute_override ) {
+			return null;
+		}
+		switch ( $attribute_override[0] ) {
+			case 0: // remove
+				/**
+				 * TODO: This currently doesn't remove the attribute, but only set it to an empty string.
+				 * It's a temporary solution until the block binding API supports different operations.
+				 */
+				return '';
+			case 1: // replace
+				return $attribute_override[1];
+			default:
+				return null;
+		}
 	};
 	wp_block_bindings_register_source(
 		'pattern_attributes',

lib/experimental/blocks.php

@@ -101,7 +101,7 @@ function gutenberg_process_block_bindings( $block_content, $block, $block_instan
 				'core/paragraph' => array( 'content' ),
 				'core/heading'   => array( 'content' ),
 				'core/image'     => array( 'url', 'title', 'alt' ),
-				'core/button'    => array( 'url', 'text' ),
+				'core/button'    => array( 'url', 'text', 'linkTarget' ),
 			);
 
 			// If the block doesn't have the bindings property or isn't one of the allowed block types, return.

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

@@ -88,6 +88,26 @@ const useInferredLayout = ( blocks, parentLayout ) => {
 	}, [ blocks, parentLayout ] );
 };
 
+/**
+ * Enum for patch operations.
+ * We use integers here to minimize the size of the serialized data.
+ * This has to be deserialized accordingly on the server side.
+ * See block-bindings/sources/pattern.php
+ */
+const PATCH_OPERATIONS = {
+	/** @type {0} */
+	Remove: 0,
+	/** @type {1} */
+	Replace: 1,
+	// Other operations are reserved for future use. (e.g. Add)
+};
+
+/**
+ * @typedef {[typeof PATCH_OPERATIONS.Remove]} RemovePatch
+ * @typedef {[typeof PATCH_OPERATIONS.Replace, unknown]} ReplacePatch
+ * @typedef {RemovePatch | ReplacePatch} OverridePatch
+ */
+
 function applyInitialOverrides( blocks, overrides = {}, defaultValues ) {
 	return blocks.map( ( block ) => {
 		const innerBlocks = applyInitialOverrides(
@@ -104,9 +124,15 @@ function applyInitialOverrides( blocks, overrides = {}, defaultValues ) {
 			defaultValues[ blockId ] ??= {};
 			defaultValues[ blockId ][ attributeKey ] =
 				block.attributes[ attributeKey ];
-			if ( overrides[ blockId ]?.[ attributeKey ] !== undefined ) {
-				newAttributes[ attributeKey ] =
-					overrides[ blockId ][ attributeKey ];
+			/** @type {OverridePatch} */
+			const overrideAttribute = overrides[ blockId ]?.[ attributeKey ];
+			if ( ! overrideAttribute ) {
+				continue;
+			}
+			if ( overrideAttribute[ 0 ] === PATCH_OPERATIONS.Remove ) {
+				delete newAttributes[ attributeKey ];
+			} else if ( overrideAttribute[ 0 ] === PATCH_OPERATIONS.Replace ) {
+				newAttributes[ attributeKey ] = overrideAttribute[ 1 ];
 			}
 		}
 		return {
@@ -118,13 +144,14 @@ function applyInitialOverrides( blocks, overrides = {}, defaultValues ) {
 }
 
 function getOverridesFromBlocks( blocks, defaultValues ) {
-	/** @type {Record<string, Record<string, unknown>>} */
+	/** @type {Record<string, Record<string, OverridePatch>>} */
 	const overrides = {};
 	for ( const block of blocks ) {
 		Object.assign(
 			overrides,
 			getOverridesFromBlocks( block.innerBlocks, defaultValues )
 		);
+		/** @type {string} */
 		const blockId = block.attributes.metadata?.id;
 		if ( ! isPartiallySynced( block ) || ! blockId ) continue;
 		const attributes = getPartiallySyncedAttributes( block );
@@ -134,10 +161,23 @@ function getOverridesFromBlocks( blocks, defaultValues ) {
 				defaultValues[ blockId ][ attributeKey ]
 			) {
 				overrides[ blockId ] ??= {};
-				// TODO: We need a way to represent `undefined` in the serialized overrides.
-				// Also see: https://github.com/WordPress/gutenberg/pull/57249#discussion_r1452987871
-				overrides[ blockId ][ attributeKey ] =
-					block.attributes[ attributeKey ];
+				/**
+				 * Create a patch operation for the binding attribute.
+				 * We use a tuple here to minimize the size of the serialized data.
+				 * The first item is the operation type, the second item is the value if any.
+				 */
+				if ( block.attributes[ attributeKey ] === undefined ) {
+					/** @type {RemovePatch} */
+					overrides[ blockId ][ attributeKey ] = [
+						PATCH_OPERATIONS.Remove,
+					];
+				} else {
+					/** @type {ReplacePatch} */
+					overrides[ blockId ][ attributeKey ] = [
+						PATCH_OPERATIONS.Replace,
+						block.attributes[ attributeKey ],
+					];
+				}
 			}
 		}
 	}

packages/patterns/src/constants.js

@@ -27,6 +27,7 @@ export const PARTIAL_SYNCING_SUPPORTED_BLOCKS = {
 	'core/button': {
 		text: __( 'Text' ),
 		url: __( 'URL' ),
+		linkTarget: __( 'Link Target' ),
 	},
 	'core/image': {
 		url: __( 'URL' ),

test/e2e/specs/editor/various/pattern-overrides.spec.js

@@ -176,7 +176,7 @@ test.describe( 'Pattern Overrides', () => {
 						ref: patternId,
 						overrides: {
 							[ editableParagraphId ]: {
-								content: 'I would word it this way',
+								content: [ 1, 'I would word it this way' ],
 							},
 						},
 					},
@@ -187,7 +187,7 @@ test.describe( 'Pattern Overrides', () => {
 						ref: patternId,
 						overrides: {
 							[ editableParagraphId ]: {
-								content: 'This one is different',
+								content: [ 1, 'This one is different' ],
 							},
 						},
 					},
@@ -263,4 +263,66 @@ test.describe( 'Pattern Overrides', () => {
 			},
 		] );
 	} );
+
+	test( 'Supports `undefined` attribute values in patterns', async ( {
+		page,
+		admin,
+		editor,
+		requestUtils,
+	} ) => {
+		const buttonId = 'button-id';
+		const { id } = await requestUtils.createBlock( {
+			title: 'Pattern with overrides',
+			content: `<!-- wp:buttons -->
+<div class="wp-block-buttons"><!-- wp:button {"metadata":{"id":"${ buttonId }","bindings":{"text":{"source":{"name":"pattern_attributes"}},"url":{"source":{"name":"pattern_attributes"}},"linkTarget":{"source":{"name":"pattern_attributes"}}}}} -->
+<div class="wp-block-button"><a class="wp-block-button__link wp-element-button" href="http://wp.org" target="_blank" rel="noreferrer noopener">wp.org</a></div>
+<!-- /wp:button --></div>
+<!-- /wp:buttons -->`,
+			status: 'publish',
+		} );
+
+		await admin.createNewPost();
+
+		await editor.insertBlock( {
+			name: 'core/block',
+			attributes: { ref: id },
+		} );
+
+		await editor.canvas
+			.getByRole( 'document', { name: 'Block: Button' } )
+			.getByRole( 'textbox', { name: 'Button text' } )
+			.focus();
+
+		await expect(
+			page.getByRole( 'link', { name: 'wp.org' } )
+		).toContainText( 'opens in a new tab' );
+
+		const openInNewTabCheckbox = page.getByRole( 'checkbox', {
+			name: 'Open in new tab',
+		} );
+		await expect( openInNewTabCheckbox ).toBeChecked();
+
+		await openInNewTabCheckbox.setChecked( false );
+
+		await expect.poll( editor.getBlocks ).toMatchObject( [
+			{
+				name: 'core/block',
+				attributes: {
+					ref: id,
+					overrides: {
+						[ buttonId ]: {
+							linkTarget: [ 0 ],
+						},
+					},
+				},
+			},
+		] );
+
+		const postId = await editor.publishPost();
+		await page.goto( `/?p=${ postId }` );
+
+		const link = page.getByRole( 'link', { name: 'wp.org' } );
+		await expect( link ).toHaveAttribute( 'href', 'http://wp.org' );
+		await expect( link ).toHaveAttribute( 'target', '' );
+	} );
 } );