Refactor how we pass the query_id and add a comment on the filter

lib/experimental/blocks.php

@@ -151,6 +151,12 @@ function gutenberg_block_core_query_add_url_filtering( $query, $block ) {
 }
 add_filter( 'query_loop_block_query_vars', 'gutenberg_block_core_query_add_url_filtering', 10, 2 );
 
+/**
+ * Adds the search query to Query blocks for the inherited queries if the instant search experiment is enabled.
+ *
+ * @param WP_Query $query The query object.
+ * @return void
+ */
 function gutenberg_block_core_query_add_search_query_filtering( $query ) {
 
 	// if the query is not the main query, return

packages/block-library/src/search/index.php

@@ -224,26 +224,28 @@ function render_block_core_search( $attributes, $content, $block ) {
 
 		wp_interactivity_config( 'core/search', array( 'canonicalURL' => $canonical_url_no_pagination ) );
 
-		$is_inherited = isset( $block->context['query']['inherit'] ) && $block->context['query']['inherit'] && ! empty( $block->context['queryId'] );
+		$query_id = $block->context['queryId'];
 		$search       = '';
 
 		// If the query is defined in the block context, use it
 		if ( isset( $block->context['query']['search'] ) && '' !== $block->context['query']['search'] ) {
 			$search = $block->context['query']['search'];
 		}
 
+		$is_inherited = isset( $block->context['query']['inherit'] ) && $block->context['query']['inherit'] && ! empty( $query_id );
+
+		// Inherited query: `instant-search=`
+		//    Custom query: `instant-search-<query_id>=`
+		$search_key = $is_inherited ? 'instant-search' : 'instant-search-' . $query_id;
+
 		// If the query is defined in the URL, it overrides the block context value.
-		if ( $is_inherited ) {
-			$search = empty( $_GET['instant-search'] ) ? $search : sanitize_text_field( $_GET['instant-search'] );
-		} else {
-			$search = empty( $_GET[ 'instant-search-' . $block->context['queryId'] ] ) ? $search : sanitize_text_field( $_GET[ 'instant-search-' . $block->context['queryId'] ] );
-		}
+		$search = empty( $_GET[ $search_key ] ) ? $search : sanitize_text_field( $_GET[ $search_key ] );
 
 		$form_context = array_merge(
 			$form_context,
 			array(
 				'search'      => $search,
-				'queryId'     => $block->context['queryId'],
+				'queryId'     => $query_id,
 				'isInherited' => $is_inherited,
 			)
 		);