Adjust Block Processor logic to only scan top-level blocks.

Author: dmsnell

src/wp-content/themes/twentytwentyone/inc/template-functions.php

@@ -371,21 +371,27 @@ function twenty_twenty_one_print_first_instance_of_block( $block_name, $content
 		$processor      = new WP_Block_Processor( $content );
 		$instance_count = 0;
 
-		if ( str_ends_with( $block_name, '*' ) ) {
-			// Scan for blocks whose block type matches the prefix.
-			$prefix = rtrim( $block_name, '*' );
-
-			while ( $instance_count < $instances && $processor->next_block() ) {
-				$matched_block_type = $processor->get_printable_block_type();
-				if ( str_starts_with( $matched_block_type, $prefix ) ) {
-					$blocks_content .= render_block( $processor->extract_full_block_and_advance() );
-					++$instance_count;
-				}
-			}
-		} else {
-			// Scan for blocks of the exact block type.
-			while ( $instance_count < $instances && $processor->next_block( $block_name ) ) {
-				$blocks_content .= render_block( $processor->extract_full_block_and_advance() );
+		// Scan for blocks whose block type matches the prefix.
+		$prefix      = rtrim( $block_name, '*' );
+		$match_fully = $prefix === $block_name;
+
+		// Loop over top-level blocks.
+		while (
+			$processor->next_block() &&
+			null !== ( $block = $processor->extract_full_block_and_advance() ) &&
+			$instance_count < $instances
+		) {
+			if (
+				/*
+				 * Prefix matches with a wildcard require printing the block name,
+				 * while full block-type matching can be delegated to the processor.
+				 * In each case, the condition only holds when the match is successful.
+				 */
+				$match_fully
+					? $processor->is_block_type( $block_name )
+					: str_starts_with( $processor->get_printable_block_type(), $prefix )
+			) {
+				$blocks_content .= render_block( $block );
 				++$instance_count;
 			}
 		}