Refactor metadata merging in resolve_pattern_blocks function

Improves the handling of metadata for single-root patterns by ensuring that existing metadata is preserved while integrating new attributes such as `name`, `description`, and `categories`. Updates unit tests to reflect the changes in metadata structure, ensuring accurate representation of merged metadata.

Author: ramonjd

src/wp-includes/blocks.php

@@ -1883,28 +1883,37 @@ function resolve_pattern_blocks( $blocks ) {
 
 			$blocks_to_insert = parse_blocks( trim( $pattern['content'] ) );
 
+			$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.
-			 * If the pattern has metadata, merge it with the existing metadata.
-			 */
+			* 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 ) {
-				$block_metadata = $blocks_to_insert[0]['attrs']['metadata'] ?? array();
-				$metadata       = array( 'patternName' => $slug );
+				$block_metadata                = $blocks_to_insert[0]['attrs']['metadata'] ?? array();
+				$block_metadata['patternName'] = $slug;
 
+				/*
+				* Merge pattern metadata with existing block metadata.
+				* Pattern metadata takes precedence, but existing block metadata
+				* is preserved as a fallback when the pattern doesn't define that field.
+				* Only the defined fields (name, description, categories) are updated;
+				* other metadata keys are preserved.
+				*/
 				foreach ( array(
-					'name'        => 'title',
+					'name'        => 'title', // 'title' is the field in the pattern object 'name' is the field in the block metadata.
 					'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 )
+						$block_metadata[ $key ] = 'categories' === $key && is_array( $value )
 							? array_map( 'sanitize_text_field', $value )
 							: sanitize_text_field( $value );
 					}
 				}
 
-				$blocks_to_insert[0]['attrs']['metadata'] = $metadata;
+				$blocks_to_insert[0]['attrs']['metadata'] = $block_metadata;
 			}
 
 			$seen_refs[ $slug ] = true;

tests/phpunit/tests/blocks/resolvePatternBlocks.php

@@ -154,7 +154,7 @@ public function data_should_resolve_pattern_blocks_as_expected() {
 			// 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 -->',
+				'<!-- wp:paragraph {"metadata":{"patternName":"core/existing-metadata","description":"A existing metadata pattern.","categories":["cake"],"name":"Existing Metadata Pattern"}} -->Existing metadata content<!-- /wp:paragraph -->',
 			),
 		);
 	}