REST API: Add author filtering to autosave collections.

src/wp-includes/rest-api/endpoints/class-wp-rest-autosaves-controller.php

@@ -307,6 +307,7 @@ public function get_item( $request ) {
 	 * Contains the user's autosave, for empty if it doesn't exist.
 	 *
 	 * @since 5.0.0
+	 * @since 7.2.0 Added support for the `author` parameter.
 	 *
 	 * @param WP_REST_Request $request Full details about the request.
 	 * @return WP_REST_Response|WP_Error Response object on success, or WP_Error object on failure.
@@ -321,8 +322,44 @@ public function get_items( $request ) {
 			// Return early as this handler doesn't add any response headers.
 			return new WP_REST_Response( array() );
 		}
+
 		$response  = array();
 		$parent_id = $parent->ID;
+
+		if ( ! empty( $request['author'] ) ) {
+			$autosaves = get_posts(
+				array(
+					'post_type'        => 'revision',
+					'post_status'      => 'inherit',
+					'post_parent'      => $parent_id,
+					'name'             => $parent_id . '-autosave-v1',
+					'author__in'       => $request['author'],
+					'orderby'          => array(
+						'date' => 'DESC',
+						'ID'   => 'DESC',
+					),
+					'posts_per_page'   => -1,
+					'suppress_filters' => false,
+				)
+			);
+
+			// Each author has at most one autosave; keep only the newest if not.
+			$seen_authors = array();
+
+			foreach ( $autosaves as $autosave ) {
+				if ( in_array( $autosave->post_author, $seen_authors, true ) ) {
+					continue;
+				}
+
+				$seen_authors[] = $autosave->post_author;
+
+				$data       = $this->prepare_item_for_response( $autosave, $request );
+				$response[] = $this->prepare_response_for_collection( $data );
+			}
+
+			return rest_ensure_response( $response );
+		}
+
 		$revisions = wp_get_post_revisions( $parent_id, array( 'check_enabled' => false ) );
 
 		foreach ( $revisions as $revision ) {
@@ -513,6 +550,15 @@ public function prepare_item_for_response( $item, $request ) {
 	public function get_collection_params() {
 		return array(
 			'context' => $this->get_context_param( array( 'default' => 'view' ) ),
+			'author'  => array(
+				'description' => __( 'Limit result set to autosaves assigned to specific authors.' ),
+				'type'        => 'array',
+				'items'       => array(
+					'type'    => 'integer',
+					'minimum' => 1,
+				),
+				'default'     => array(),
+			),
 		);
 	}
 }