Embeds: Provide a cached text fallback.

Sometimes, embedded sites might suffer from less than 100% uptime. Instead of leaving the embedding site with a big blank space where the embed should be, let's fall back to a link to the embedded post, so there's at least some context for the post.

Fixes #34462.



git-svn-id: https://develop.svn.wordpress.org/trunk@35437 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/default-filters.php

@@ -165,6 +165,7 @@ add_filter( 'the_title_rss',      'ent2ncr',                    8 );
 add_filter( 'the_title_rss',      'esc_html'                      );
 add_filter( 'the_content_rss',    'ent2ncr',                    8 );
 add_filter( 'the_content_feed',   'wp_staticize_emoji'            );
+add_filter( 'the_content_feed',   '_oembed_filter_feed_content'   );
 add_filter( 'the_excerpt_rss',    'convert_chars'                 );
 add_filter( 'the_excerpt_rss',    'ent2ncr',                    8 );
 add_filter( 'comment_author_rss', 'ent2ncr',                    8 );

src/wp-includes/embed-functions.php

@@ -461,7 +461,9 @@ function get_post_embed_html( $post = null, $width, $height ) {
 
 	$embed_url = get_post_embed_url( $post );
 
-	$output = "<script type='text/javascript'>\n";
+	$output = '<blockquote><a href="' . get_permalink( $post ) . '">' . get_the_title( $post ) . "</a></blockquote>\n";
+
+	$output .= "<script type='text/javascript'>\n";
 	$output .= "<!--//--><![CDATA[//><!--\n";
 	if ( SCRIPT_DEBUG ) {
 		$output .= file_get_contents( ABSPATH . WPINC . '/js/wp-embed.js' );
@@ -752,7 +754,11 @@ function wp_filter_oembed_result( $result, $data, $url ) {
 	}
 
 	$allowed_html = array(
-		'iframe' => array(
+		'a'          => array(
+			        'href' => true,
+		),
+		'blockquote' => array(),
+		'iframe'     => array(
 			'src'          => true,
 			'width'        => true,
 			'height'       => true,
@@ -766,13 +772,20 @@ function wp_filter_oembed_result( $result, $data, $url ) {
 	);
 
 	$html = wp_kses( $result, $allowed_html );
-	preg_match( '|^.*(<iframe.*?></iframe>).*$|m', $html, $iframes );
 
-	if ( empty( $iframes ) ) {
+	preg_match( '|(<blockquote>.*?</blockquote>)?.*(<iframe.*?></iframe>)|ms', $html, $content );
+	// We require at least the iframe to exist.
+	if ( empty( $content[2] ) ) {
 		return false;
 	}
+	$html = $content[1] . $content[2];
 
-	$html = str_replace( '<iframe', '<iframe sandbox="allow-scripts" security="restricted"', $iframes[1] );
+	if ( ! empty( $content[1] ) ) {
+		// We have a blockquote to fall back on. Hide the iframe by default.
+		$html = str_replace( '<iframe', '<iframe style="display:none;"', $html );
+	}
+
+	$html = str_replace( '<iframe', '<iframe sandbox="allow-scripts" security="restricted"', $html );
 
 	preg_match( '/ src=[\'"]([^\'"]*)[\'"]/', $html, $results );
 
@@ -782,6 +795,7 @@ function wp_filter_oembed_result( $result, $data, $url ) {
 		$url = esc_url( "{$results[1]}#?secret=$secret" );
 
 		$html = str_replace( $results[0], " src=\"$url\" data-secret=\"$secret\"", $html );
+		$html = str_replace( '<blockquote', "<blockquote data-secret=\"$secret\"", $html );
 	}
 
 	return $html;
@@ -910,3 +924,16 @@ function print_embed_scripts() {
 	</script>
 	<?php
 }
+
+/**
+ * Prepare the oembed HTML to be displayed in an RSS feed.
+ *
+ * @since 4.4.0
+ * @access private
+ *
+ * @param string $content The content to filter.
+ * @return string The filtered content.
+ */
+function _oembed_filter_feed_content( $content ) {
+	return str_replace( '<iframe sandbox="allow-scripts" security="restricted" style="display:none;"', '<iframe sandbox="allow-scripts" security="restricted"', $content );
+}

src/wp-includes/js/wp-embed.js

@@ -13,14 +13,22 @@
 			return;
 		}
 
-		var iframes = document.querySelectorAll( '.wp-embedded-content[data-secret="' + data.secret + '"]' );
+		var iframes = document.querySelectorAll( 'iframe[data-secret="' + data.secret + '"]' ),
+			blockquotes = document.querySelectorAll( 'blockquote[data-secret="' + data.secret + '"]' ),
+			i, source, height, sourceURL, targetURL;
 
-		for ( var i = 0; i < iframes.length; i++ ) {
+		for ( i = 0; i < blockquotes.length; i++ ) {
-			var source = iframes[ i ];
+			blockquotes[ i ].style.display = 'none';
+		}
+
+		for ( i = 0; i < iframes.length; i++ ) {
+			source = iframes[ i ];
+
+			source.style.display = '';
 
 			/* Resize the iframe on request. */
 			if ( 'height' === data.message ) {
-				var height = data.value;
+				height = data.value;
 				if ( height > 1000 ) {
 					height = 1000;
 				} else if ( height < 200 ) {
@@ -32,7 +40,9 @@
 
 			/* Link to a specific URL on request. */
 			if ( 'link' === data.message ) {
-				var sourceURL = document.createElement( 'a' ), targetURL = document.createElement( 'a' );
+				sourceURL = document.createElement( 'a' );
+				targetURL = document.createElement( 'a' );
+
 				sourceURL.href = source.getAttribute( 'src' );
 				targetURL.href = data.value;
 
@@ -48,13 +58,14 @@
 
 	function onLoad() {
 		var isIE10 = -1 !== navigator.appVersion.indexOf( 'MSIE 10' ),
-			isIE11 = !!navigator.userAgent.match( /Trident.*rv\:11\./ );
+			isIE11 = !!navigator.userAgent.match( /Trident.*rv\:11\./ ),
+			iframes, iframeClone, i;
 
 		/* Remove security attribute from iframes in IE10 and IE11. */
 		if ( isIE10 || isIE11 ) {
-			var iframes = document.querySelectorAll( '.wp-embedded-content[security]' ), iframeClone;
+			iframes = document.querySelectorAll( '.wp-embedded-content[security]' );
 
-			for ( var i = 0; i < iframes.length; i++ ) {
+			for ( i = 0; i < iframes.length; i++ ) {
 				iframeClone = iframes[ i ].cloneNode( true );
 				iframeClone.removeAttribute( 'security' );
 				iframes[ i ].parentNode.insertBefore( iframeClone, iframes[ i ].nextSibling );

tests/phpunit/tests/oembed/filterResult.php

@@ -78,4 +78,18 @@ EOD;
 		$this->assertFalse( wp_filter_oembed_result( false, (object) array( 'type' => 'rich' ), '' ) );
 		$this->assertFalse( wp_filter_oembed_result( '', (object) array( 'type' => 'rich' ), '' ) );
 	}
+
+	function test_filter_oembed_result_blockquote_adds_style_to_iframe() {
+		$html   = '<blockquote></blockquote><iframe></iframe>';
+		$actual = wp_filter_oembed_result( $html, (object) array( 'type' => 'rich' ), '' );
+
+		$this->assertEquals( '<blockquote></blockquote><iframe sandbox="allow-scripts" security="restricted" style="display:none;"></iframe>', $actual );
+	}
+
+	function test_filter_oembed_result_allowed_html() {
+		$html   = '<blockquote><strong><a href="" target=""></a></strong></blockquote><iframe></iframe>';
+		$actual = wp_filter_oembed_result( $html, (object) array( 'type' => 'rich' ), '' );
+
+		$this->assertEquals( '<blockquote><a href=""></a></blockquote><iframe sandbox="allow-scripts" security="restricted" style="display:none;"></iframe>', $actual );
+	}
 }