Ticket #58773: 58773.diff

src/wp-includes/class-wp-oembed.php

@@ -414 +414 @@
                         return false;
                 }
 
+                // Lazy load oEmbed iframes.
+                if ( wp_lazy_loading_enabled( 'iframe', 'oembed' ) && isset( $data->html ) && str_starts_with( $data->html, '<iframe' ) && ! str_contains( $data->html, 'loading' ) ) {
+                        $data->html = wp_iframe_tag_add_loading_attr( $data->html, 'oembed' );
+                }
+
                 /**
                  * Filters the HTML returned by the oEmbed provider.
                  *

tests/phpunit/tests/oembed/controller.php

@@ -813 +813 @@
 
                 $this->assertStringStartsWith( '<b>Unfiltered</b>', $data->html );
         }
+
+        /**
+         * Test that oembed iframes are lazy loaded by default.
+         */
+        public function test_oembed_iframes_are_lazy_loaded_by_default() {
+                wp_set_current_user( self::$editor );
+                $post = self::factory()->post->create_and_get(
+                        array(
+                                'post_author'  => self::$editor,
+                                'post_title'   => 'Hello World',
+                                'post_content' => 'https://www.youtube.com/watch?v=' . self::YOUTUBE_VIDEO_ID,
+                        )
+                );
+
+                // Get the post content via the REST API.
+                $request = new WP_REST_Request( 'GET', '/wp/v2/posts/' . $post->ID );
+                $request->set_param( '_embed', true );
+                $response = rest_get_server()->dispatch( $request );
+                $data     = $response->get_data();
+
+                $this->assertIsArray( $data );
+                $this->assertStringContainsString( 'loading="lazy"', $data['content']['rendered'] );
+        }
 }