Ping IndexNow for newly 404ing URLs. (#160)

Signed-off-by: Peter Wilson <git-commit-by@peterwilson.cc>
Signed-off-by: Ryan McCue <me@ryanmccue.info>
Co-authored-by: Ryan McCue <me@ryanmccue.info>

inc/pings/namespace.php

@@ -109,18 +109,51 @@ function handle_key_file_request() {
  * @param WP_Post $post       Post object.
  */
 function ping_indexnow( $new_status, $old_status, $post ) : void {
-	// Only ping for published posts.
+	/*
-	if ( 'publish' !== $new_status ) {
+	 * Skip if post type isn't viewable.
+	 *
+	 * The post type shouldn't change under normal circumstances,
+	 * so it's safe to assume that both the old and new post are
+	 * not viewable.
+	 */
+	if ( ! is_post_type_viewable( $post->post_type ) ) {
 		return;
 	}
 
-	// Skip revisions and autosaves.
+	/*
+	 * Skip for revisions and autosaves.
+	 *
+	 * The IndexNow ping for revisions will be handled by the
+	 * parent post's transition_post_status hook.
+	 */
 	if ( wp_is_post_revision( $post ) || wp_is_post_autosave( $post ) ) {
 		return;
 	}
 
-	// Skip non-public post types.
+	/*
-	if ( ! is_post_type_viewable( $post->post_type ) ) {
+	 * Skip if both old and new statuses are private.
+	 *
+	 * The page will have been a 404 before and after.
+	 *
+	 * For pages that are newly a 404, still ping IndexNow
+	 * to encourage removal of the URL from search engines.
+	 */
+	if (
+		! is_post_status_viewable( $new_status )
+		&& ! is_post_status_viewable( $old_status )
+	) {
+		return;
+	}
+
+	/*
+	 * Prevent double pings for block editor legacy meta boxes.
+	 */
+	if (
+		// phpcs:ignore WordPress.Security.NonceVerification.Recommended
+		isset( $_GET['meta-box-loader'] )
+		// phpcs:ignore WordPress.Security.NonceVerification.Recommended, WordPress.PHP.StrictComparisons.LooseComparison -- form input.
+		&& '1' == $_GET['meta-box-loader']
+	) {
 		return;
 	}