Issue #3453745 by kentr: Filter has false positives

js/highlightjs_input_filter.js

@@ -9,7 +9,8 @@ import hljs from 'https://unpkg.com/@highlightjs/cdn-assets@11.8.0/es/core.min.j
   const initEvent = new Event("highlightjs:init");
   const promises = Object.values(languages).map(language => {
     return import(`https://unpkg.com/@highlightjs/cdn-assets@11.8.0/es/languages/${language}.min.js`)
-      .then(module => hljs.registerLanguage(language, module.default));
+      .then(module => hljs.registerLanguage(language, module.default))
+      .catch(e => console.error(`${e.name}: ${e.message}`));
   });
 
   if (drupalSettings.enableCopyButton == true) {

src/Plugin/Filter/HighlightJs.php

@@ -23,21 +23,23 @@ class HighlightJs extends FilterBase {
   public function process($text, $langcode) {
     $enable_copy_button = \Drupal::config('highlightjs_input_filter.settings')->get('enable_copy_button');
     $result = new FilterProcessResult($text);
-    if (stristr($text, '<code') === FALSE || stristr($text, 'language-') === FALSE) {
+
+    // Regex approximates the className regex in highlight.js itself,
+    // also matching the containing `<pre><code>` tags.
+    // Using a DOM parser as highlight.js does would probably be cleaner.
+    $pattern = '/<pre>\s*<code\s+class="\s*(?:[\w-]+\s+)?\b[\w-]*lang(?:uage)?-([\w-]+)\b/i';
+
+    // If no matches are found, return early.
+    if (!preg_match_all($pattern, $result, $matches)) {
       return $result;
     }
 
-    $pattern = "/language-[^\"]+/i";
-    if (preg_match_all($pattern, $result, $matches)) {
-      foreach ($matches as $match) {
-        foreach ($match as $language_id) {
-          $language = str_replace('language-', '', $language_id);
-          // Create a uniquely keyed array of languages so the
-          // BubbleableMetadata->mergeAttachments() method can properly
-          // merge the drupalSettings when adding attachments.
-          $languages[$language] = $language;
-        }
-      }
+    // If matches are found, process.
+    foreach ($matches[1] as $language) {
+      // Create a uniquely keyed array of languages so the
+      // BubbleableMetadata->mergeAttachments() method can properly
+      // merge the drupalSettings when adding attachments.
+      $languages[$language] = $language;
     }
 
     $result->addCacheableDependency($enable_copy_button);