Better error for invalid code-block language

Author: weaverryan

src/Directive/CodeBlockDirective.php

@@ -6,6 +6,7 @@
 use Doctrine\RST\Nodes\CodeNode;
 use Doctrine\RST\Nodes\Node;
 use Doctrine\RST\Parser;
+use SymfonyDocsBuilder\Renderers\CodeNodeRenderer;
 
 class CodeBlockDirective extends Directive
 {
@@ -20,6 +21,10 @@ public function process(Parser $parser, ?Node $node, string $variable, string $d
             return;
         }
 
+        if (!CodeNodeRenderer::isLanguageSupported($data)) {
+            throw new \Exception(sprintf('Unsupported code block language "%s"', $data));
+        }
+
         $node->setLanguage($data);
 
         if ('' !== $variable) {

src/Renderers/CodeNodeRenderer.php

@@ -16,6 +16,7 @@ class CodeNodeRenderer implements NodeRenderer
         'html+twig'       => 'twig',
         'jinja'           => 'twig',
         'html+php'        => 'html',
+        'xml+php'         => 'xml',
         'php-annotations' => 'php',
         'terminal'        => 'bash',
         'rst'             => 'markdown',
@@ -71,6 +72,17 @@ public function render(): string
         );
     }
 
+    public static function isLanguageSupported(string $lang): bool
+    {
+        $highlighter = new Highlighter();
+        $supportedLanguages = array_merge(
+            array_keys(self::LANGUAGES_MAPPING),
+            $highlighter->listLanguages(true)
+        );
+
+        return in_array($lang, $supportedLanguages);
+    }
+
     private function getLines(string $code): array
     {
         $lines         = preg_split('/\r\n|\r|\n/', $code);

tests/Renderers/CodeNodeRendererTest.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace SymfonyDocsBuilder\Tests\Renderers;
+
+use PHPUnit\Framework\TestCase;
+use SymfonyDocsBuilder\Renderers\CodeNodeRenderer;
+
+class CodeNodeRendererTest extends TestCase
+{
+    /**
+     * @dataProvider getSupportedLanguageTests
+     */
+    public function testIsLanguageSupported(string $lang, bool $shouldBeSupported)
+    {
+        $this->assertSame($shouldBeSupported, CodeNodeRenderer::isLanguageSupported($lang));
+    }
+
+    public function getSupportedLanguageTests()
+    {
+        yield 'normal_lang' => ['xml', true];
+        yield 'aliased_lang' => ['php-annotations', true];
+        yield 'unsupported' => ['bhb', false];
+    }
+}