Ticket #58773: 58773.2.diff

src/wp-includes/default-filters.php

@@ -668 +668 @@
 add_action( 'wp_head', 'wp_oembed_add_discovery_links' );
 add_action( 'wp_head', 'wp_oembed_add_host_js' ); // Back-compat for sites disabling oEmbed host JS by removing action.
 add_filter( 'embed_oembed_html', 'wp_maybe_enqueue_oembed_host_js' );
+add_filter( 'embed_oembed_html', 'wp_lazy_load_oembed_iframe' );
 
 add_action( 'embed_head', 'enqueue_embed_scripts', 1 );
 add_action( 'embed_head', 'print_emoji_detection_script' );

src/wp-includes/embed.php

@@ -1244 +1244 @@
 
         return $result;
 }
+
+/**
+ * Apply the loading="lazy" attribute to the oEmbed iframe.
+ *
+ * @since 6.4.0
+ *
+ * @param string $html The oEmbed HTML, usually containing an iframe.
+ *
+ * @return string The oEmbed HTML with the loading="lazy" attribute added to the iframe.
+ */
+function wp_lazy_load_oembed_iframe( $html ) {
+        $tag_parser = new WP_HTML_Tag_Processor( $html );
+        if ( wp_lazy_loading_enabled( 'iframe', 'oembed' ) && isset( $html ) && $tag_parser->next_tag( 'iframe' ) && ! $tag_parser->get_attribute( 'loading' ) ) {
+                $html = wp_iframe_tag_add_loading_attr( $html, 'oembed' );
+        }
+
+        return $html;
+}

tests/phpunit/tests/oembed/WpEmbed.php

@@ -9 +9 @@
          */
         protected $wp_embed;
 
+        const YOUTUBE_VIDEO_ID = 'OQSNhk5ICTI';
+
         public function set_up() {
                 parent::set_up();
                 $this->wp_embed = new WP_Embed();
@@ -377 +379 @@
                 $this->wp_embed->linkifunknown = false;
                 $this->assertSame( $url, $this->wp_embed->maybe_make_link( $url ) );
         }
+
+        /**
+         * Test that oembed iframes are lazy loaded by default.
+         *
+         * @ticket 58773
+         */
+        public function test_oembed_iframes_are_lazy_loaded_by_default() {
+                $url    = 'https://www.youtube.com/watch?v=' . self::YOUTUBE_VIDEO_ID;
+                $actual = $this->wp_embed->run_shortcode( '[embed]' . $url . '[/embed]' );
+                $this->assertContains( 'loading="lazy"', $actual );
+        }
+
 }

tests/phpunit/tests/oembed/wpOembed.php

@@ -9 +9 @@
          */
         protected $oembed;
 
+        const YOUTUBE_VIDEO_ID = 'OQSNhk5ICTI';
+
         public $pre_oembed_result_filtered = false;
 
         public function set_up() {
@@ -237 +239 @@
                 $this->assertFalse( $actual );
                 $this->assertSame( $current_blog_id, get_current_blog_id() );
         }
+
 }