feat(import/markdown): preserve language tags when possible

src/services/import/markdown.ts

@@ -1,17 +1,41 @@
 "use strict";
 
-import { parse } from "marked";
+import { parse, Renderer, type Tokens } from "marked";
+
+const renderer = new Renderer({ async: false });
+renderer.code = ({text, lang, escaped}: Tokens.Code) => {
+    if (!text) {
+        return "";
+    }
+
+    const ckEditorLanguage = getNormalizedMimeFromMarkdownLanguage(lang);
+    return `<pre><code class="language-${ckEditorLanguage}">${text}</code></pre>`;
+};
+
 import htmlSanitizer from "../html_sanitizer.js";
 import importUtils from "./utils.js";
+import { getMimeTypeFromHighlightJs, MIME_TYPE_AUTO, normalizeMimeTypeForCKEditor } from "../../public/app/services/mime_type_definitions.js";
 
 function renderToHtml(content: string, title: string) {
     const html = parse(content, {
-        async: false
+        async: false,
+        renderer: renderer
     }) as string;
     const h1Handled = importUtils.handleH1(html, title); // h1 handling needs to come before sanitization
     return htmlSanitizer.sanitize(h1Handled);
 }
 
+function getNormalizedMimeFromMarkdownLanguage(language: string | undefined) {
+    if (language) {
+        const highlightJsName = getMimeTypeFromHighlightJs(language);
+        if (highlightJsName) {
+            return normalizeMimeTypeForCKEditor(highlightJsName.mime);
+        }
+    }
+
+    return MIME_TYPE_AUTO;
+}
+
 export default {
     renderToHtml
 };