Update wp_add_lazy_load_attributes()

Filter eachg tag after adding the `loading` attribute.
Change priority to 25, after other "display" filters.

Author: azaozz

Diff for: wp-lazy-loading.php

@@ -32,10 +32,8 @@
 function _wp_lazy_loading_initialize_filters() {
 	// The following filters would be merged into core.
 	foreach ( array( 'the_content', 'the_excerpt', 'comment_text', 'widget_text_content' ) as $filter ) {
-		// Before parsing blocks and shortcodes.
-		// TODO: Comments do not support images. Revisit.
-		// TODO: This should not exclude images from dynamic blocks and shortcodes. Look at fixing the filter priority.
-		add_filter( $filter, 'wp_add_lazy_load_attributes', 8 );
+		// After parsing blocks and shortcodes.
+		add_filter( $filter, 'wp_add_lazy_load_attributes', 25 );
 	}
 
 	// The following filters are only needed while this is a feature plugin.
@@ -119,8 +117,6 @@ function wp_lazy_loading_enabled( $tag_name, $context ) {
 	return (bool) apply_filters( 'wp_lazy_loading_enabled', $default, $tag_name, $context );
 }
 
-
-// TODO: update docs.
 /**
  * Add `loading="lazy"` to `img` and/or `iframe` HTML tags.
  *
@@ -129,7 +125,7 @@ function wp_lazy_loading_enabled( $tag_name, $context ) {
  *
  * @since (TBD)
  *
- * @param string $content The raw post content to be filtered.
+ * @param string $content The HTML content to be filtered.
  * @param string $context Optional. Additional context to pass to the filters. Defaults to `current_filter()` when not set.
  * @return string Converted content with 'loading' attributes added to images.
  */
@@ -149,23 +145,44 @@ function wp_add_lazy_load_attributes( $content, $context = null ) {
 		$tags[] = 'iframe';
 	}
 
+	// Check if the tag exists in $content.
+	foreach ( $tags as $index => $tag_name ) {
+		if ( false === strpos( $content, "<$tag_name" ) ) {
+			unset( $tags[ $index ] );
+		}
+	}
+
 	if ( empty( $tags ) ) {
 		return $content;
 	}
 
 	return preg_replace_callback(
-		'/<(' . implode( '|', $tags ) . ')(\s)[^>]+>/',
-		function( array $matches ) {
-			if ( ! preg_match( '/\sloading\s*=/', $matches[0] ) ) {
-				$tag   = $matches[1];
-				$space = $matches[2];
-
-				return str_replace( '<' . $tag . $space, '<' . $tag . $space . 'loading="lazy" ', $matches[0] );
+		'/<(' . implode( '|', $tags ) . ')\s[^>]+>/',
+		function( array $matches ) use( $content, $context ) {
+			if ( ! preg_match( '/\bloading\s*=/', $matches[0] ) ) {
+				$tag_name = $matches[1];
+				$old_html = $matches[0];
+
+				$new_html = str_replace( "<$tag_name", "<$tag_name" . ' loading="lazy"', $old_html );
+
+				/**
+				 * Filters the tag HTML after adding the `loading` attribute.
+				 *
+				 * The variable part of the filter name is the filtered tag's name. For example for `img`
+				 * the filter would become `wp_add_lazy_loading_to_img`.
+				 *
+				 * @since (TBD)
+				 *
+				 * @param string $new_html The tag's HTML after adding the attribute.
+				 * @param string $old_html The tag's HTML before adding the attribute.
+				 * @param string $content The HTML content that is being filtered.
+				 * @param string $context Optional. Additional context. Defaults to `current_filter()`.
+				 */
+				return apply_filters( "wp_add_lazy_loading_to_{$tag_name}", $new_html, $old_html, $content, $context );
 			}
 
 			return $matches[0];
 		},
 		$content
 	);
 }
-