[6.x] Use CommonMark For Mailable (#30982)

This switches Markdown Mailable parsing to CommonMark instead of Parsedown. The main reason for this is better granularity of security related features in CommonMark, which allows us to prevent unsafe links in user input (a user input with the content: "a") without needing to prevent all HTML tags in general which would break our current mailable system.

I think it would be good to do this basically security related change on 6.x because it is an LTS.

composer.json

@@ -22,7 +22,8 @@
         "doctrine/inflector": "^1.1",
         "dragonmantank/cron-expression": "^2.0",
         "egulias/email-validator": "^2.1.10",
-        "erusev/parsedown": "^1.7",
+        "league/commonmark": "^1.1",
+        "league/commonmark-ext-table": "^2.1",
         "league/flysystem": "^1.0.8",
         "monolog/monolog": "^1.12|^2.0",
         "nesbot/carbon": "^2.0",

src/Illuminate/Mail/Markdown.php

@@ -5,7 +5,9 @@
 use Illuminate\Contracts\View\Factory as ViewFactory;
 use Illuminate\Support\HtmlString;
 use Illuminate\Support\Str;
-use Parsedown;
+use League\CommonMark\CommonMarkConverter;
+use League\CommonMark\Environment;
+use League\CommonMark\Ext\Table\TableExtension;
 use TijsVerkoyen\CssToInlineStyles\CssToInlineStyles;
 
 class Markdown
@@ -98,9 +100,15 @@ public function renderText($view, array $data = [])
      */
     public static function parse($text)
     {
-        $parsedown = new Parsedown;
+        $environment = Environment::createCommonMarkEnvironment();
 
-        return new HtmlString($parsedown->text($text));
+        $environment->addExtension(new TableExtension);
+
+        $converter = new CommonMarkConverter([
+            'allow_unsafe_links' => false,
+        ], $environment);
+
+        return new HtmlString($converter->convertToHtml($text));
     }
 
     /**

src/Illuminate/Mail/composer.json

@@ -16,7 +16,8 @@
     "require": {
         "php": "^7.2",
         "ext-json": "*",
-        "erusev/parsedown": "^1.7",
+        "league/commonmark": "^1.1",
+        "league/commonmark-ext-table": "^2.1",
         "illuminate/container": "^6.0",
         "illuminate/contracts": "^6.0",
         "illuminate/support": "^6.0",

tests/Mail/MailMarkdownTest.php

@@ -66,6 +66,6 @@ public function testParseReturnsParsedMarkdown()
 
         $result = $markdown->parse('# Something')->toHtml();
 
-        $this->assertSame('<h1>Something</h1>', $result);
+        $this->assertSame("<h1>Something</h1>\n", $result);
     }
 }