Enhance metadata handling in resolve_pattern_blocks function

Refines the logic for merging metadata in single-root patterns, ensuring that existing metadata is preserved and new attributes such as `name`, `description`, and `categories` are correctly integrated. Updates unit tests to validate the new behavior, including a test for preserving existing metadata.

Author: ramonjd

src/wp-includes/blocks.php

@@ -1883,22 +1883,25 @@ function resolve_pattern_blocks( $blocks ) {
 
 			$blocks_to_insert = parse_blocks( trim( $pattern['content'] ) );
 
-			// For single-root patterns, add the pattern name to make this a pattern instance in the editor.
+			/*
+			 * For single-root patterns, add the pattern name to make this a pattern instance in the editor.
+			 * If the pattern has metadata, merge it with the existing metadata.
+			 */
 			if ( count( $blocks_to_insert ) === 1 ) {
-				$metadata = array(
-					'patternName' => $slug,
-				);
-
-				if ( ! empty( $pattern['title'] ) ) {
-					$metadata['name'] = sanitize_text_field( $pattern['title'] );
-				}
-
-				if ( ! empty( $pattern['description'] ) ) {
-					$metadata['description'] = sanitize_text_field( $pattern['description'] );
-				}
-
-				if ( ! empty( $pattern['categories'] ) && is_array( $pattern['categories'] ) ) {
-					$metadata['categories'] = array_map( 'sanitize_text_field', $pattern['categories'] );
+				$block_metadata = $blocks_to_insert[0]['attrs']['metadata'] ?? array();
+				$metadata       = array( 'patternName' => $slug );
+
+				foreach ( array(
+					'name'        => 'title',
+					'description' => 'description',
+					'categories'  => 'categories',
+				) as $key => $pattern_key ) {
+					$value = $pattern[ $pattern_key ] ?? $block_metadata[ $key ] ?? null;
+					if ( $value ) {
+						$metadata[ $key ] = 'categories' === $key && is_array( $value )
+							? array_map( 'sanitize_text_field', $value )
+							: sanitize_text_field( $value );
+					}
 				}
 
 				$blocks_to_insert[0]['attrs']['metadata'] = $metadata;

tests/phpunit/tests/blocks/resolvePatternBlocks.php

@@ -71,6 +71,13 @@ public function set_up() {
 				'categories'  => array( 'featured' ),
 			)
 		);
+		register_block_pattern(
+			'core/existing-metadata',
+			array(
+				'title'       => 'Existing Metadata Pattern',
+				'content'     => '<!-- wp:paragraph {"metadata":{"patternName":"core/existing-metadata-should-not-overwrite","description":"A existing metadata pattern.","categories":["cake"]}} -->Existing metadata content<!-- /wp:paragraph -->',
+			)
+		);
 	}
 
 	public function tear_down() {
@@ -143,6 +150,11 @@ public function data_should_resolve_pattern_blocks_as_expected() {
 				'<!-- wp:pattern {"slug":"core/single-root-with-forbidden-chars-in-attrs"} /-->',
 				'<!-- wp:paragraph {"metadata":{"patternName":"core/single-root-with-forbidden-chars-in-attrs","name":"Single Root Pattern","description":"A single root pattern.","categories":["text","bad\'); DROP TABLE wp_posts;\u002d\u002d","","evil\u0000null byte","category with html tags"]}} -->Single root content<!-- /wp:paragraph -->',
 			),
+			// Metadata is merged with existing metadata and existing metadata is preserved.
+			'existing metadata preserved'   => array(
+				'<!-- wp:pattern {"slug":"core/existing-metadata"} /-->',
+				'<!-- wp:paragraph {"metadata":{"patternName":"core/existing-metadata","name":"Existing Metadata Pattern","description":"A existing metadata pattern.","categories":["cake"]}} -->Existing metadata content<!-- /wp:paragraph -->',
+			),
 		);
 	}
 }