Add GestureRecognizer to children of 'a' Tag (flutter#9)

* Add GestureRecognizer to children of 'a' Tag

* Add support links with nested items

* Add test for nested elements in links

* Add onTap tests

Author: xqwzts

packages/flutter_markdown/lib/src/builder.dart

@@ -73,6 +73,8 @@ class MarkdownBuilder implements md.NodeVisitor {
   final List<String> _listIndents = <String>[];
   final List<_BlockElement> _blocks = <_BlockElement>[];
   final List<_InlineElement> _inlines = <_InlineElement>[];
+  final List<GestureRecognizer> _linkHandlers = <GestureRecognizer>[];
+
 
   /// Returns widgets that display the given Markdown nodes.
   ///
@@ -81,6 +83,7 @@ class MarkdownBuilder implements md.NodeVisitor {
     _listIndents.clear();
     _blocks.clear();
     _inlines.clear();
+    _linkHandlers.clear();
 
     _blocks.add(new _BlockElement(null));
     _inlines.add(new _InlineElement());
@@ -98,8 +101,12 @@ class MarkdownBuilder implements md.NodeVisitor {
   void visitText(md.Text text) {
     if (_blocks.last.tag == null) // Don't allow text directly under the root.
       return;
-    final TextSpan span = _blocks.last.tag == 'pre' ?
-      delegate.formatText(styleSheet, text.text) : new TextSpan(text: text.text);
+    final TextSpan span = _blocks.last.tag == 'pre'
+      ? delegate.formatText(styleSheet, text.text)
+      : new TextSpan(
+          text: text.text,
+          recognizer: _linkHandlers.isNotEmpty ? _linkHandlers.last : null,
+        );
     _inlines.last.children.add(span);
   }
 
@@ -114,6 +121,11 @@ class MarkdownBuilder implements md.NodeVisitor {
     } else {
       _inlines.add(new _InlineElement());
     }
+
+    if (tag == 'a') {
+      _linkHandlers.add(delegate.createLink(element.attributes['href']));
+    }
+
     return true;
   }
 
@@ -179,16 +191,14 @@ class MarkdownBuilder implements md.NodeVisitor {
       final _InlineElement parent = _inlines.last;
 
       if (current.children.isNotEmpty) {
-        GestureRecognizer recognizer;
-
-        if (tag == 'a')
-          recognizer = delegate.createLink(element.attributes['href']);
-
         parent.children.add(new TextSpan(
           style: styleSheet.styles[tag],
-          recognizer: recognizer,
           children: current.children,
         ));
+
+        if (tag == 'a') {
+          _linkHandlers.removeLast();
+        }
       }
     }
   }

packages/flutter_markdown/test/flutter_markdown_test.dart

@@ -85,16 +85,83 @@ void main() {
     ]);
   });
 
-  testWidgets('Links', (WidgetTester tester) async {
-    await tester
-        .pumpWidget(_boilerplate(const Markdown(data: '[Link Text](href)')));
-
-    final RichText textWidget =
-    tester.allWidgets.firstWhere((Widget widget) => widget is RichText);
-    final TextSpan span = textWidget.text;
-
-    expect(
-        span.children[0].recognizer.runtimeType, equals(TapGestureRecognizer));
+  group('Links', () {
+    testWidgets('Single link', (WidgetTester tester) async {
+      String tapResult;
+      await tester.pumpWidget(_boilerplate(new Markdown(
+        data: '[Link Text](href)',
+        onTapLink: (value) => tapResult = value,
+      )));
+
+      final RichText textWidget =
+          tester.allWidgets.firstWhere((Widget widget) => widget is RichText);
+      final TextSpan span = textWidget.text;
+
+      (span.children[0].children[0].recognizer as TapGestureRecognizer).onTap();
+
+      expect(span.children.length, 1);
+      expect(span.children[0].children.length, 1);
+      expect(span.children[0].children[0].recognizer.runtimeType,
+          equals(TapGestureRecognizer));
+      expect(tapResult, 'href');
+    });
+
+    testWidgets('Link with nested code', (WidgetTester tester) async {
+      final List<String> tapResults = <String>[];
+      await tester.pumpWidget(_boilerplate(new Markdown(
+        data: '[Link `with nested code` Text](href)',
+        onTapLink: (value) => tapResults.add(value),
+      )));
+
+      final RichText textWidget =
+          tester.allWidgets.firstWhere((Widget widget) => widget is RichText);
+      final TextSpan span = textWidget.text;
+
+      final List<Type> gestureRecognizerTypes = <Type>[];
+      span.visitTextSpan((TextSpan textSpan) {
+        TapGestureRecognizer recognizer = textSpan.recognizer;
+        gestureRecognizerTypes.add(recognizer.runtimeType);
+        recognizer.onTap();
+        return true;
+      });
+
+      expect(span.children.length, 1);
+      expect(span.children[0].children.length, 3);
+      expect(gestureRecognizerTypes, everyElement(TapGestureRecognizer));
+      expect(tapResults.length, 3);
+      expect(tapResults, everyElement('href'));
+    });
+
+    testWidgets('Multiple links', (WidgetTester tester) async {
+      final List<String> tapResults = <String>[];
+
+      await tester.pumpWidget(_boilerplate(new Markdown(
+          data: '[First Link](firstHref) and [Second Link](secondHref)',
+          onTapLink: (value) => tapResults.add(value),
+      )));
+
+      final RichText textWidget =
+          tester.allWidgets.firstWhere((Widget widget) => widget is RichText);
+      final TextSpan span = textWidget.text;
+
+      final List<Type> gestureRecognizerTypes = <Type>[];
+      span.visitTextSpan((TextSpan textSpan) {
+        TapGestureRecognizer recognizer = textSpan.recognizer;
+        gestureRecognizerTypes.add(recognizer.runtimeType);
+        recognizer?.onTap();
+        return true;
+      });
+
+
+      expect(span.children.length, 3);
+      expect(span.children[0].children.length, 1);
+      expect(span.children[1].children, null);
+      expect(span.children[2].children.length, 1);
+
+      expect(gestureRecognizerTypes,
+          orderedEquals([TapGestureRecognizer, Null, TapGestureRecognizer]));
+      expect(tapResults, orderedEquals(['firstHref', 'secondHref']));
+    });
   });
 
   testWidgets('HTML tag ignored ', (WidgetTester tester) async {