Merge pull request #1074 from kyrias/only-highlight-specified-language

Only syntax highlight if language was specified

src/HtmlUtils.js

@@ -124,6 +124,7 @@ var sanitizeHtmlParams = {
         // would make sense if we did
         img: ['src'],
         ol: ['start'],
+        code: ['class'], // We don't actually allow all classes, we filter them in transformTags
     },
     // Lots of these won't come up by default because we don't allow them
     selfClosing: ['img', 'br', 'hr', 'area', 'base', 'basefont', 'input', 'link', 'meta'],
@@ -165,6 +166,19 @@ var sanitizeHtmlParams = {
             attribs.rel = 'noopener'; // https://mathiasbynens.github.io/rel-noopener/
             return { tagName: tagName, attribs : attribs };
         },
+        'code': function(tagName, attribs) {
+            if (typeof attribs.class !== 'undefined') {
+                // Filter out all classes other than ones starting with language- for syntax highlighting.
+                let classes = attribs.class.split(/\s+/).filter(function(cl) {
+                    return cl.startsWith('language-');
+                });
+                attribs.class = classes.join(' ');
+            }
+            return {
+                tagName: tagName,
+                attribs: attribs,
+            };
+        },
         '*': function(tagName, attribs) {
             // Delete any style previously assigned, style is an allowedTag for font and span
             // because attributes are stripped after transforming

src/components/structures/UserSettings.js

@@ -93,6 +93,10 @@ const SETTINGS_LABELS = [
         id: 'disableMarkdown',
         label: 'Disable markdown formatting',
     },
+    {
+        id: 'enableSyntaxHighlightLanguageDetection',
+        label: 'Enable automatic language detection for syntax highlighting',
+    },
 /*
     {
         id: 'useFixedWidthFont',

src/components/views/messages/TextualBody.js

@@ -29,6 +29,7 @@ import Modal from '../../../Modal';
 import SdkConfig from '../../../SdkConfig';
 import dis from '../../../dispatcher';
 import { _t } from '../../../languageHandler';
+import UserSettingsStore from "../../../UserSettingsStore";
 
 linkifyMatrix(linkify);
 
@@ -90,7 +91,18 @@ module.exports = React.createClass({
                 setTimeout(() => {
                     if (this._unmounted) return;
                     for (let i = 0; i < blocks.length; i++) {
-                        highlight.highlightBlock(blocks[i]);
+                        if (UserSettingsStore.getSyncedSetting("enableSyntaxHighlightLanguageDetection", false)) {
+                            highlight.highlightBlock(blocks[i])
+                        } else {
+                            // Only syntax highlight if there's a class starting with language-
+                            let classes = blocks[i].className.split(/\s+/).filter(function (cl) {
+                                return cl.startsWith('language-');
+                            });
+
+                            if (classes.length != 0) {
+                                highlight.highlightBlock(blocks[i]);
+                            }
+                        }
                     }
                 }, 10);
             }

src/i18n/strings/en_EN.json

@@ -268,6 +268,7 @@
   "Email address (optional)": "Email address (optional)",
   "Email, name or matrix ID": "Email, name or matrix ID",
   "Emoji": "Emoji",
+  "Enable automatic language detection for syntax highlighting": "Enable automatic language detection for syntax highlighting",
   "Enable encryption": "Enable encryption",
   "Enable Notifications": "Enable Notifications",
   "enabled": "enabled",