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-connections', $gutenberg_experiments ) ) {
+	/**
+	 * Registers the dynamicContent 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( 'dynamicContent', $block_type->uses_context, true ) ) {
+				$block_type->uses_context[] = 'dynamicContent';
+			}
+		}
+	}
+
+	// Register the block support.
+	WP_Block_Supports::get_instance()->register(
+		'pattern',
+		array(
+			'register_attribute' => 'gutenberg_register_pattern_support',
+		)
+	);
+}

lib/experimental/blocks.php

@@ -132,9 +132,8 @@ 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;
 			}
 
@@ -154,6 +153,10 @@ function gutenberg_render_block_connections( $block_content, $block, $block_inst
 				$attribute_value['value']
 			);
 
+			if ( false === $custom_value ) {
+				continue;
+			}
+
 			$tags  = new WP_HTML_Tag_Processor( $block_content );
 			$found = $tags->next_tag(
 				array(
@@ -181,5 +184,6 @@ 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 +6,13 @@
  */
 
 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, $meta_field ) {
+		return _wp_array_get( $block_instance->context, array( 'dynamicContent', $meta_field ), false );
+	},
 );

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

@@ -2,7 +2,7 @@
  * WordPress dependencies
  */
 import { addFilter } from '@wordpress/hooks';
-import { PanelBody, TextControl } from '@wordpress/components';
+import { PanelBody, TextControl, SelectControl } from '@wordpress/components';
 import { __, sprintf } from '@wordpress/i18n';
 import { hasBlockSupport } from '@wordpress/blocks';
 import { createHigherOrderComponent } from '@wordpress/compose';
@@ -47,45 +47,71 @@ function CustomFieldsControl( props ) {
 	if ( props.name === 'core/paragraph' ) attributeName = 'content';
 	if ( props.name === 'core/image' ) attributeName = 'url';
 
+	const connectionSource =
+		props.attributes?.connections?.attributes?.[ attributeName ]?.source ||
+		'';
+	const connectionValue =
+		props.attributes?.connections?.attributes?.[ attributeName ]?.value ||
+		'';
+
+	function updateConnections( source, value ) {
+		if ( value === '' ) {
+			props.setAttributes( {
+				connections: undefined,
+				placeholder: undefined,
+			} );
+		} else {
+			props.setAttributes( {
+				connections: {
+					attributes: {
+						// The attributeName will be either `content` or `url`.
+						[ attributeName ]: {
+							// Source will be variable, could be post_meta, user_meta, term_meta, etc.
+							// Could even be a custom source like a social media attribute.
+							source,
+							value,
+						},
+					},
+				},
+				placeholder: sprintf(
+					'This content will be replaced on the frontend by the value of "%s" custom field.',
+					value
+				),
+			} );
+		}
+	}
+
 	return (
 		<InspectorControls>
 			<PanelBody title={ __( 'Connections' ) } initialOpen={ true }>
+				<SelectControl
+					label={ __( 'Source' ) }
+					value={ connectionSource }
+					options={ [
+						{
+							label: __( 'None' ),
+							value: '',
+						},
+						{
+							label: __( 'Meta fields' ),
+							value: 'meta_fields',
+						},
+						{
+							label: __( 'Pattern attributes' ),
+							value: 'pattern_attributes',
+						},
+					] }
+					onChange={ ( nextSource ) => {
+						updateConnections( nextSource, connectionValue );
+					} }
+				/>
 				<TextControl
 					__nextHasNoMarginBottom
 					autoComplete="off"
 					label={ __( 'Custom field meta_key' ) }
-					value={
-						props.attributes?.connections?.attributes?.[
-							attributeName
-						]?.value || ''
-					}
+					value={ connectionValue }
 					onChange={ ( nextValue ) => {
-						if ( nextValue === '' ) {
-							props.setAttributes( {
-								connections: undefined,
-								[ attributeName ]: undefined,
-								placeholder: undefined,
-							} );
-						} else {
-							props.setAttributes( {
-								connections: {
-									attributes: {
-										// The attributeName will be either `content` or `url`.
-										[ attributeName ]: {
-											// Source will be variable, could be post_meta, user_meta, term_meta, etc.
-											// Could even be a custom source like a social media attribute.
-											source: 'meta_fields',
-											value: nextValue,
-										},
-									},
-								},
-								[ attributeName ]: undefined,
-								placeholder: sprintf(
-									'This content will be replaced on the frontend by the value of "%s" custom field.',
-									nextValue
-								),
-							} );
-						}
+						updateConnections( connectionSource, nextValue );
 					} }
 				/>
 			</PanelBody>

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 ) ) ) {