Improve user ID fallback and transformer logic (#2246)

Author: pfefferle

.github/changelog/2246-from-description

@@ -0,0 +1,4 @@
+Significance: patch
+Type: fixed
+
+Posts now only fall back to the blog user when blog mode is enabled and no valid author exists, ensuring content negotiation only runs if an Actor is available.

includes/functions.php

@@ -1300,12 +1300,24 @@ function get_content_warning( $post_id ) {
 /**
  * Get the ActivityPub ID of a User by the WordPress User ID.
  *
+ * Fall back to blog user if in blog mode or if user is not found.
+ *
  * @param int $id The WordPress User ID.
  *
- * @return string The ActivityPub ID (a URL) of the User.
+ * @return string|false The ActivityPub ID (a URL) of the User or false if not found.
  */
 function get_user_id( $id ) {
-	$user = Actors::get_by_id( $id );
+	$mode = \get_option( 'activitypub_actor_mode', 'default' );
+
+	if ( ACTIVITYPUB_BLOG_MODE === $mode ) {
+		$user = Actors::get_by_id( Actors::BLOG_USER_ID );
+	} else {
+		$user = Actors::get_by_id( $id );
+
+		if ( \is_wp_error( $user ) ) {
+			$user = Actors::get_by_id( Actors::BLOG_USER_ID );
+		}
+	}
 
 	if ( \is_wp_error( $user ) ) {
 		return false;

includes/transformer/class-factory.php

@@ -11,6 +11,7 @@
 use Activitypub\Comment as Comment_Helper;
 use Activitypub\Http;
 
+use function Activitypub\get_user_id;
 use function Activitypub\is_post_disabled;
 use function Activitypub\user_can_activitypub;
 
@@ -90,7 +91,7 @@ public static function get_transformer( $data ) {
 			case 'WP_Post':
 				if ( 'attachment' === $data->post_type && ! is_post_disabled( $data ) ) {
 					return new Attachment( $data );
-				} elseif ( ! is_post_disabled( $data ) ) {
+				} elseif ( ! is_post_disabled( $data ) && get_user_id( $data->post_author ) ) {
 					return new Post( $data );
 				}
 				break;

tests/includes/class-test-functions.php

@@ -712,6 +712,17 @@ public function test_get_user_id() {
 		$user->add_cap( 'activitypub' );
 
 		$this->assertIsString( \Activitypub\get_user_id( $user->ID ) );
+
+		\add_option( 'activitypub_actor_mode', ACTIVITYPUB_ACTOR_MODE );
+
+		$this->assertIsString( \Activitypub\get_user_id( $user->ID ) );
+
+		$user->remove_cap( 'activitypub' );
+		\update_option( 'activitypub_actor_mode', ACTIVITYPUB_BLOG_MODE );
+		$this->assertIsString( \Activitypub\get_user_id( $user->ID ) );
+
+		\update_option( 'activitypub_actor_mode', ACTIVITYPUB_ACTOR_MODE );
+		$this->assertFalse( \Activitypub\get_user_id( $user->ID ) );
 	}
 
 	/**

tests/includes/transformer/class-test-factory.php

@@ -13,14 +13,13 @@
 use Activitypub\Transformer\Factory;
 use Activitypub\Transformer\Json;
 use Activitypub\Transformer\Post;
-use WP_UnitTestCase;
 
 /**
  * Test class for Transformer Factory.
  *
  * @coversDefaultClass \Activitypub\Transformer\Factory
  */
-class Test_Factory extends WP_UnitTestCase {
+class Test_Factory extends \WP_UnitTestCase {
 	/**
 	 * Test post ID.
 	 *
@@ -113,6 +112,20 @@ public function test_get_transformer_post() {
 		$post        = get_post( self::$post_id );
 		$transformer = Factory::get_transformer( $post );
 
+		$this->assertInstanceOf( \WP_Error::class, $transformer );
+
+		\add_option( 'activitypub_actor_mode', ACTIVITYPUB_ACTOR_AND_BLOG_MODE );
+
+		$post        = get_post( self::$post_id );
+		$transformer = Factory::get_transformer( $post );
+
+		$this->assertInstanceOf( Post::class, $transformer );
+
+		\add_option( 'activitypub_actor_mode', ACTIVITYPUB_ACTOR_MODE );
+
+		$post        = get_post( self::$post_id );
+		$transformer = Factory::get_transformer( $post );
+
 		$this->assertInstanceOf( Post::class, $transformer );
 	}