Added data-lang attribute for CommonMark code block renderer

Author: Alex Garrett-Smith

src/CommonMark/CodeBlockRenderer.php

@@ -38,7 +38,7 @@ public function render(Node $node, ChildNodeRendererInterface $childRenderer)
         if ($theme instanceof WithPre) {
             return $theme->preBefore() . $parsed . $theme->preAfter();
         } else {
-            return '<pre>' . $parsed . '</pre>';
+            return '<pre data-lang="' . $matches['language'] . '">' . $parsed . '</pre>';
         }
     }
 }

tests/CommonMark/CodeBlockRendererTest.php

@@ -32,6 +32,7 @@ class Foo {}
         ```");
 
         $this->assertStringContainsString('hl-keyword', $parsed->getContent());
+        $this->assertStringContainsString('data-lang="php"', $parsed->getContent());
     }
 
     public function test_commonmark_with_gutter(): void
@@ -52,7 +53,7 @@ class Foo {}
 TXT;
 
         $expected = <<<'TXT'
-<pre><span class="hl-gutter ">10</span> <span class="hl-keyword">class</span> <span class="hl-type">Foo</span> {}</pre>
+<pre data-lang="php"><span class="hl-gutter ">10</span> <span class="hl-keyword">class</span> <span class="hl-type">Foo</span> {}</pre>
 
 TXT;