Implement partially synced patterns behind an experimental flag

lib/block-supports/pattern.php

@@ -0,0 +1,36 @@
+<?php
+/**
+ * Pattern block support flag.
+ *
+ * @package gutenberg
+ */
+
+$gutenberg_experiments = get_option( 'gutenberg-experiments' );
+if ( $gutenberg_experiments && array_key_exists( 'gutenberg-pattern-partial-syncing', $gutenberg_experiments ) ) {
+	/**
+	 * Registers the overrides context for block types that support it.
+	 *
+	 * @param WP_Block_Type $block_type Block Type.
+	 */
+	function gutenberg_register_pattern_support( $block_type ) {
+		$pattern_support = property_exists( $block_type, 'supports' ) ? _wp_array_get( $block_type->supports, array( '__experimentalConnections' ), false ) : false;
+
+		if ( $pattern_support ) {
+			if ( ! $block_type->uses_context ) {
+				$block_type->uses_context = array();
+			}
+
+			if ( ! in_array( 'pattern/overrides', $block_type->uses_context, true ) ) {
+				$block_type->uses_context[] = 'pattern/overrides';
+			}
+		}
+	}
+
+	// Register the block support.
+	WP_Block_Supports::get_instance()->register(
+		'pattern',
+		array(
+			'register_attribute' => 'gutenberg_register_pattern_support',
+		)
+	);
+}

lib/experimental/blocks.php

@@ -82,7 +82,10 @@ function wp_enqueue_block_view_script( $block_name, $args ) {
 
 
 $gutenberg_experiments = get_option( 'gutenberg-experiments' );
-if ( $gutenberg_experiments && array_key_exists( 'gutenberg-connections', $gutenberg_experiments ) ) {
+if ( $gutenberg_experiments && (
+	array_key_exists( 'gutenberg-connections', $gutenberg_experiments ) ||
+	array_key_exists( 'gutenberg-pattern-partial-syncing', $gutenberg_experiments )
+) ) {
 	/**
 	 * Renders the block meta attributes.
 	 *
@@ -132,9 +135,8 @@ function gutenberg_render_block_connections( $block_content, $block, $block_inst
 				continue;
 			}
 
-			// If the source value is not "meta_fields", skip it because the only supported
-			// connection source is meta (custom fields) for now.
-			if ( 'meta_fields' !== $attribute_value['source'] ) {
+			// Skip if the source value is not "meta_fields" or "pattern_attributes".
+			if ( 'meta_fields' !== $attribute_value['source'] && 'pattern_attributes' !== $attribute_value['source'] ) {
 				continue;
 			}
 
@@ -143,16 +145,28 @@ function gutenberg_render_block_connections( $block_content, $block, $block_inst
 				continue;
 			}
 
-			// If the attribute does not specify the name of the custom field, skip it.
-			if ( ! isset( $attribute_value['value'] ) ) {
-				continue;
+			if ( 'pattern_attributes' === $attribute_value['source'] ) {
+				if ( ! _wp_array_get( $block_instance->attributes, array( 'metadata', 'id' ), false ) ) {
+					continue;
+				}
+
+				$custom_value = $connection_sources[ $attribute_value['source'] ]( $block_instance );
+			} else {
+				// If the attribute does not specify the name of the custom field, skip it.
+				if ( ! isset( $attribute_value['value'] ) ) {
+					continue;
+				}
+
+				// Get the content from the connection source.
+				$custom_value = $connection_sources[ $attribute_value['source'] ](
+					$block_instance,
+					$attribute_value['value']
+				);
 			}
 
-			// Get the content from the connection source.
-			$custom_value = $connection_sources[ $attribute_value['source'] ](
-				$block_instance,
-				$attribute_value['value']
-			);
+			if ( false === $custom_value ) {
+				continue;
+			}
 
 			$tags  = new WP_HTML_Tag_Processor( $block_content );
 			$found = $tags->next_tag(
@@ -181,5 +195,6 @@ function gutenberg_render_block_connections( $block_content, $block, $block_inst
 
 		return $block_content;
 	}
+
 	add_filter( 'render_block', 'gutenberg_render_block_connections', 10, 3 );
 }

lib/experimental/connection-sources/index.php

@@ -6,10 +6,14 @@
  */
 
 return array(
-	'name'        => 'meta',
-	'meta_fields' => function ( $block_instance, $meta_field ) {
+	'name'               => 'meta',
+	'meta_fields'        => function ( $block_instance, $meta_field ) {
 		// We should probably also check if the meta field exists but for now it's okay because
 		// if it doesn't, `get_post_meta()` will just return an empty string.
 		return get_post_meta( $block_instance->context['postId'], $meta_field, true );
 	},
+	'pattern_attributes' => function ( $block_instance ) {
+		$block_id = $block_instance->attributes['metadata']['id'];
+		return _wp_array_get( $block_instance->context, array( 'pattern/overrides', $block_id ), false );
+	},
 );

lib/experimental/editor-settings.php

@@ -33,6 +33,10 @@ function gutenberg_enable_experiments() {
 	if ( gutenberg_is_experiment_enabled( 'gutenberg-no-tinymce' ) ) {
 		wp_add_inline_script( 'wp-block-library', 'window.__experimentalDisableTinymce = true', 'before' );
 	}
+
+	if ( $gutenberg_experiments && array_key_exists( 'gutenberg-pattern-partial-syncing', $gutenberg_experiments ) ) {
+		wp_add_inline_script( 'wp-block-editor', 'window.__experimentalPatternPartialSyncing = true', 'before' );
+	}
 }
 
 add_action( 'admin_init', 'gutenberg_enable_experiments' );

lib/experiments-page.php

@@ -138,6 +138,18 @@ function gutenberg_initialize_experiments_settings() {
 		)
 	);
 
+	add_settings_field(
+		'gutenberg-pattern-partial-syncing',
+		__( 'Synced patterns partial syncing', 'gutenberg' ),
+		'gutenberg_display_experiment_field',
+		'gutenberg-experiments',
+		'gutenberg_experiments_section',
+		array(
+			'label' => __( 'Test partial syncing of patterns', 'gutenberg' ),
+			'id'    => 'gutenberg-pattern-partial-syncing',
+		)
+	);
+
 	register_setting(
 		'gutenberg-experiments',
 		'gutenberg-experiments'

lib/load.php

@@ -270,6 +270,7 @@ function () {
 require __DIR__ . '/block-supports/shadow.php';
 require __DIR__ . '/block-supports/background.php';
 require __DIR__ . '/block-supports/behaviors.php';
+require __DIR__ . '/block-supports/pattern.php';
 
 // Data views.
 require_once __DIR__ . '/experimental/data-views.php';

packages/block-editor/src/hooks/custom-fields.js

@@ -128,12 +128,17 @@ const withCustomFieldsControls = createHigherOrderComponent( ( BlockEdit ) => {
 	};
 }, 'withCustomFieldsControls' );
 
-if ( window.__experimentalConnections ) {
+if (
+	window.__experimentalConnections ||
+	window.__experimentalPatternPartialSyncing
+) {
 	addFilter(
 		'blocks.registerBlockType',
 		'core/editor/connections/attribute',
 		addAttribute
 	);
+}
+if ( window.__experimentalConnections ) {
 	addFilter(
 		'editor.BlockEdit',
 		'core/editor/connections/with-inspector-controls',

packages/block-editor/src/store/private-actions.js

@@ -290,3 +290,11 @@ export function deleteStyleOverride( id ) {
 		id,
 	};
 }
+
+export function syncDerivedBlockAttributes( clientId, attributes ) {
+	return {
+		type: 'SYNC_DERIVED_BLOCK_ATTRIBUTES',
+		clientIds: [ clientId ],
+		attributes,
+	};
+}

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

@@ -283,6 +283,7 @@ const withBlockTree =
 					false
 				);
 				break;
+			case 'SYNC_DERIVED_BLOCK_ATTRIBUTES':
 			case 'UPDATE_BLOCK_ATTRIBUTES': {
 				newState.tree = new Map( newState.tree );
 				action.clientIds.forEach( ( clientId ) => {
@@ -456,6 +457,12 @@ function withPersistentBlockChange( reducer ) {
 	return ( state, action ) => {
 		let nextState = reducer( state, action );
 
+		if ( action.type === 'SYNC_DERIVED_BLOCK_ATTRIBUTES' ) {
+			return nextState.isPersistentChange
+				? { ...nextState, isPersistentChange: false }
+				: nextState;
+		}
+
 		const isExplicitPersistentChange =
 			action.type === 'MARK_LAST_CHANGE_AS_PERSISTENT' ||
 			markNextChangeAsNotPersistent;
@@ -860,6 +867,7 @@ export const blocks = pipe(
 				return newState;
 			}
 
+			case 'SYNC_DERIVED_BLOCK_ATTRIBUTES':
 			case 'UPDATE_BLOCK_ATTRIBUTES': {
 				// Avoid a state change if none of the block IDs are known.
 				if ( action.clientIds.every( ( id ) => ! state.get( id ) ) ) {