Fix to prefer no-highlight class over language-* class

Related-to: rehypejs/rehype#154.

lib/index.js

@@ -155,26 +155,31 @@ export default function rehypeHighlight(options) {
  *   is used.
  */
 function language(node) {
-  const className = node.properties.className
+  const list = node.properties.className
   let index = -1
 
-  if (!Array.isArray(className)) {
+  if (!Array.isArray(list)) {
     return
   }
 
-  while (++index < className.length) {
-    const value = String(className[index])
+  /** @type {string | undefined} */
+  let name
+
+  while (++index < list.length) {
+    const value = String(list[index])
 
     if (value === 'no-highlight' || value === 'nohighlight') {
       return false
     }
 
-    if (value.slice(0, 5) === 'lang-') {
-      return value.slice(5)
+    if (!name && value.slice(0, 5) === 'lang-') {
+      name = value.slice(5)
     }
 
-    if (value.slice(0, 9) === 'language-') {
-      return value.slice(9)
+    if (!name && value.slice(0, 9) === 'language-') {
+      name = value.slice(9)
     }
   }
+
+  return name
 }

test.js

@@ -267,6 +267,23 @@ test('rehypeHighlight', async function (t) {
     )
   })
 
+  await t.test(
+    'should prefer `no-highlight` over a `language-*` class',
+    async function () {
+      const file = await rehype()
+        .data('settings', {fragment: true})
+        .use(rehypeHighlight)
+        .process(
+          '<h1>Hello World!</h1>\n<pre><code class="lang-js no-highlight">alert(1)</code></pre>'
+        )
+
+      assert.equal(
+        String(file),
+        '<h1>Hello World!</h1>\n<pre><code class="lang-js no-highlight">alert(1)</code></pre>'
+      )
+    }
+  )
+
   await t.test('should not highlight (`nohighlight`)', async function () {
     const file = await rehype()
       .data('settings', {fragment: true})