feat: add emptyLangClass option (#343)

README.md

@@ -23,6 +23,7 @@ import hljs from 'highlight.js';
 // const {markedHighlight} = globalThis.markedHighlight;
 const marked = new Marked(
   markedHighlight({
+	emptyLangClass: 'hljs',
     langPrefix: 'hljs language-',
     highlight(code, lang, info) {
       const language = hljs.getLanguage(lang) ? lang : 'plaintext';
@@ -87,4 +88,5 @@ const highlight = "code";
 |--------|--------|---------|:------------|
 | async  | boolean | `false` | If the highlight function returns a promise set this to `true`. Don't forget to `await` the call to `marked.parse` |
 | langPrefix | string | `'language-'` | A prefix to add to the class of the `code` tag. |
+| emptyLangClass | string | `''` | The class to add to the `code` tag if the language is empty. |
 | highlight | function | `(code: string, lang: string) => {}` | Required. The function to transform the code to html. |

spec/index.test.js

@@ -239,6 +239,34 @@ no language provided
     expect(await marked(markdownWithoutLang)).toMatchInlineSnapshot(`
 "<pre><code>
 </code></pre>"
+`);
+  });
+
+  test('nullish infostring is cast to emptyLangClass option', () => {
+    marked.use(markedHighlight({
+      emptyLangClass: 'empty',
+      highlight(code, lang, info) {
+        expect(info).toBe('');
+        return info;
+      },
+    }));
+    expect(marked(markdownWithoutLang)).toMatchInlineSnapshot(`
+"<pre><code class="empty">
+</code></pre>"
+`);
+  });
+
+  test('no class when emptyLangClass is empty string', () => {
+    marked.use(markedHighlight({
+      emptyLangClass: '',
+      highlight(code, lang, info) {
+        expect(info).toBe('');
+        return info;
+      },
+    }));
+    expect(marked(markdownWithoutLang)).toMatchInlineSnapshot(`
+"<pre><code>
+</code></pre>"
 `);
   });
 });

src/index.d.ts

@@ -41,6 +41,11 @@ declare module 'marked-highlight' {
      * appended to this to form the class attribute added to the <code> element.
      */
     langPrefix?: string;
+    /**
+     * The class attribute added to the <code> element if the language tag is
+     * empty.
+     */
+    emptyLangClass?: string;
   }
 
   /**
@@ -61,6 +66,11 @@ declare module 'marked-highlight' {
      * appended to this to form the class attribute added to the <code> element.
      */
     langPrefix?: string;
+    /**
+     * The class attribute added to the <code> element if the language tag is
+     * empty.
+     */
+    emptyLangClass?: string;
   }
 
   /**

src/index.js

@@ -13,6 +13,10 @@ export function markedHighlight(options) {
     options.langPrefix = 'language-';
   }
 
+  if (typeof options.emptyLangClass !== 'string') {
+    options.emptyLangClass = '';
+  }
+
   return {
     async: !!options.async,
     walkTokens(token) {
@@ -42,8 +46,9 @@ export function markedHighlight(options) {
           code = code.text;
         }
         const lang = getLang(infoString);
-        const classAttr = lang
-          ? ` class="${options.langPrefix}${escape(lang)}"`
+        const classValue = lang ? options.langPrefix + escape(lang) : options.emptyLangClass;
+        const classAttr = classValue
+          ? ` class="${classValue}"`
           : '';
         code = code.replace(/\n$/, '');
         return `<pre><code${classAttr}>${escaped ? code : escape(code, true)}\n</code></pre>`;