Filter searches by allowed post types if post_type is not set (#2816)

Fixes #2815

wp-content/themes/pub/wporg-learn-2024/inc/block-config.php

@@ -54,7 +54,8 @@ function get_content_type_options( $options ) {
 		'lesson' => __( 'Lesson', 'wporg-learn' ),
 	);
 
-	$selected_slug = $wp_query->get( 'post_type' ) ? $wp_query->get( 'post_type' ) : 'any';
+	$post_type = $wp_query->get( 'post_type' );
+	$selected_slug = is_string( $post_type ) ? $post_type : 'any';
 	$label = $options[ $selected_slug ] ?? $options['any'];
 
 	return array(

wp-content/themes/pub/wporg-learn-2024/inc/query.php

@@ -7,6 +7,7 @@
 
 add_action( 'pre_get_posts', __NAMESPACE__ . '\add_language_to_archive_queries' );
 add_action( 'pre_get_posts', __NAMESPACE__ . '\add_excluded_to_lesson_archive_query' );
+add_action( 'pre_get_posts', __NAMESPACE__ . '\filter_search_queries_by_post_type' );
 add_filter( 'request', __NAMESPACE__ . '\handle_all_level_query' );
 
 /**
@@ -80,6 +81,23 @@ function add_excluded_to_lesson_archive_query( $query ) {
 	}
 }
 
+/**
+ * Filter search queries by post type.
+ * Only include courses and lessons in search results unless post_type is set, eg. for an archive search.
+ *
+ * @param WP_Query $query The query object.
+ * @return WP_Query The modified query object.
+ */
+function filter_search_queries_by_post_type( $query ) {
+	if ( ! is_admin() && $query->is_search() && $query->is_main_query() ) {
+		if ( ! $query->get( 'post_type' ) ) {
+			$query->set( 'post_type', array( 'course', 'lesson' ) );
+		}
+	}
+
+	return $query;
+}
+
 /**
  * Modify the request.
  *