Add fallback to trigger create on update failure (#2328)

Author: pfefferle

.github/changelog/2328-from-description

@@ -0,0 +1,4 @@
+Significance: minor
+Type: added
+
+Added fallback to trigger create handling when updates fail for missing posts or comments, ensuring objects are properly created.

includes/collection/class-posts.php

@@ -84,8 +84,8 @@ public static function get_by_guid( $guid ) {
 
 		if ( ! $post_id ) {
 			return new \WP_Error(
-				'activitypub_object_not_found',
-				\__( 'Object not found', 'activitypub' ),
+				'activitypub_post_not_found',
+				\__( 'Post not found', 'activitypub' ),
 				array( 'status' => 404 )
 			);
 		}

includes/handler/class-update.php

@@ -22,16 +22,17 @@ class Update {
 	 * Initialize the class, registering WordPress hooks.
 	 */
 	public static function init() {
-		\add_action( 'activitypub_inbox_update', array( self::class, 'handle_update' ), 10, 2 );
+		\add_action( 'activitypub_inbox_update', array( self::class, 'handle_update' ), 10, 3 );
 	}
 
 	/**
 	 * Handle "Update" requests.
 	 *
-	 * @param array $activity The Activity object.
-	 * @param int   $user_id  The user ID. Always null for Update activities.
+	 * @param array                          $activity        The Activity object.
+	 * @param int                            $user_id         The user ID. Always null for Update activities.
+	 * @param \Activitypub\Activity\Activity $activity_object The activity object. Default null.
 	 */
-	public static function handle_update( $activity, $user_id ) {
+	public static function handle_update( $activity, $user_id, $activity_object ) {
 		$object_type = $activity['object']['type'] ?? '';
 
 		switch ( $object_type ) {
@@ -60,7 +61,7 @@ public static function handle_update( $activity, $user_id ) {
 			case 'Video':
 			case 'Event':
 			case 'Document':
-				self::update_object( $activity, $user_id );
+				self::update_object( $activity, $user_id, $activity_object );
 				break;
 
 			/*
@@ -76,21 +77,42 @@ public static function handle_update( $activity, $user_id ) {
 	/**
 	 * Update an Object.
 	 *
-	 * @param array $activity The Activity object.
-	 * @param int   $user_id  The user ID. Always null for Update activities.
+	 * @param array                          $activity        The Activity object.
+	 * @param int                            $user_id         The user ID. Always null for Update activities.
+	 * @param \Activitypub\Activity\Activity $activity_object The activity object. Default null.
 	 */
-	public static function update_object( $activity, $user_id ) {
-		$result = new \WP_Error( 'activitypub_update_failed', 'Update failed' );
+	public static function update_object( $activity, $user_id, $activity_object ) {
+		$result  = new \WP_Error( 'activitypub_update_failed', 'Update failed' );
+		$updated = true;
 
 		// Check for private and/or direct messages.
 		if ( is_activity_reply( $activity ) ) {
 			$comment_data = Interactions::update_comment( $activity );
 
-			if ( ! empty( $comment_data['comment_ID'] ) ) {
+			if ( false === $comment_data ) {
+				$updated = false;
+			} elseif ( ! empty( $comment_data['comment_ID'] ) ) {
 				$result = \get_comment( $comment_data['comment_ID'] );
 			}
 		} else {
 			$result = Posts::update( $activity );
+
+			if ( \is_wp_error( $result ) && 'activitypub_post_not_found' === $result->get_error_code() ) {
+				$updated = false;
+			}
+		}
+
+		// There is no object to update, try to trigger create instead.
+		if ( ! $updated ) {
+			/**
+			 * Fires when a Create activity is received for an existing object.
+			 *
+			 * @param array                          $activity        The activity-object.
+			 * @param int                            $user_id         The id of the local blog-user.
+			 * @param \Activitypub\Activity\Activity $activity_object The activity object.
+			 */
+			\do_action( 'activitypub_inbox_create', $activity, $user_id, $activity_object );
+			return false;
 		}
 
 		$success = ( $result && ! \is_wp_error( $result ) );

tests/phpunit/tests/includes/handler/class-test-update.php

@@ -19,6 +19,44 @@
  */
 class Test_Update extends \WP_UnitTestCase {
 
+	/**
+	 * Test that the activitypub_inbox_create fallback is triggered.
+	 */
+	public function test_activitypub_inbox_create_fallback() {
+		$called     = false;
+		$test_actor = 'https://example.com/users/fallback';
+		$activity   = array(
+			'id'     => 'https://example.com/activities/12345',
+			'type'   => 'Create',
+			'actor'  => $test_actor,
+			'object' => array(
+				'id'      => 'https://example.com/objects/12345',
+				'type'    => 'Note',
+				'content' => 'Test note',
+			),
+		);
+
+		// Add a fallback handler for the action.
+		\add_action(
+			'activitypub_inbox_create',
+			function ( $activity_data ) use ( &$called, $test_actor ) {
+				if ( isset( $activity_data['actor'] ) && $activity_data['actor'] === $test_actor ) {
+					$called = true;
+				}
+			},
+			10,
+			3
+		);
+
+		// Call the handler (simulate inbox create for unknown type).
+		\do_action( 'activitypub_inbox_update', $activity, $this->user_id, null );
+
+		$this->assertTrue( $called, 'The fallback activitypub_inbox_create action should be triggered.' );
+
+		// Clean up by removing the action.
+		\remove_all_actions( 'activitypub_inbox_create' );
+	}
+
 	/**
 	 * User ID.
 	 *