Add support for brackets in link text to markdown codecs

packages/parchment/lib/src/codecs/markdown.dart

@@ -35,7 +35,7 @@ class _ParchmentMarkdownDecoder extends Converter<String, ParchmentDocument> {
     r'(`(?<inline_code_text>.+?)`)',
   );
 
-  static final _linkRegExp = RegExp(r'\[([^\]]+)\]\(([^)]+)\)');
+  static final _linkRegExp = RegExp(r'\[(.+?)\]\(([^)]+)\)');
   static final _ulRegExp = RegExp(r'^( *)\* +(.*)');
   static final _olRegExp = RegExp(r'^( *)\d+[.)] +(.*)');
   static final _clRegExp = RegExp(r'^( *)- +\[( |x|X)\] +(.*)');

packages/parchment/test/codecs/markdown_test.dart

@@ -242,6 +242,23 @@ void main() {
       expect(andBack, markdown);
     });
 
+    test('complex link', () {
+      final markdown =
+          'This a complex link [1[2(3) 4]5 6](https://github.com/[abc]) and [normal one](https://github.com)\n\n';
+      final document = parchmentMarkdown.decode(markdown);
+      final delta = document.toDelta();
+
+      expect(delta.elementAt(1).data, '1[2(3) 4]5 6');
+      expect(delta.elementAt(1).attributes?['b'], null);
+      expect(delta.elementAt(1).attributes?['a'], 'https://github.com/[abc]');
+
+      expect(delta.elementAt(3).data, 'normal one');
+      expect(delta.elementAt(3).attributes?['a'], 'https://github.com');
+
+      final andBack = parchmentMarkdown.encode(document);
+      expect(andBack, markdown);
+    });
+
     test('style around link', () {
       final markdown =
           'This **house** is a **[circus](https://github.com)**\n\n';