msglist: In single-conversation view, make recipient headers not tappable.

Fixes: #1171

Author: lakshya1goel

lib/widgets/message_list.dart

@@ -1108,7 +1108,13 @@ class StreamMessageRecipientHeader extends StatelessWidget {
         ]));
 
     return GestureDetector(
-      onTap: () => Navigator.push(context,
+      // When already in a topic narrow, disable tap interaction that would just
+      // push a MessageListPage for the same topic narrow.
+      // TODO(#1039) simplify by removing topic-narrow condition if we remove
+      //   recipient headers in topic narrows
+      onTap: (narrow is TopicNarrow)
+        ? null
+        : () => Navigator.push(context,
         MessageListPage.buildRoute(context: context,
           narrow: TopicNarrow.ofMessage(message))),
       onLongPress: () => showTopicActionSheet(context,
@@ -1157,7 +1163,13 @@ class DmRecipientHeader extends StatelessWidget {
     final messageListTheme = MessageListTheme.of(context);
 
     return GestureDetector(
-      onTap: () => Navigator.push(context,
+      // When already in a DM narrow, disable tap interaction that would just
+      // push a MessageListPage for the same DM narrow.
+      // TODO(#1244) simplify by removing DM-narrow condition if we remove
+      //   recipient headers in DM narrows
+      onTap: (narrow is DmNarrow)
+        ? null
+        : () => Navigator.push(context,
         MessageListPage.buildRoute(context: context,
           narrow: DmNarrow.ofMessage(message, selfUserId: store.selfUserId))),
       child: ColoredBox(

test/widgets/message_list_test.dart

@@ -923,6 +923,53 @@ void main() {
         await tester.pump();
         tester.widget(find.text('new stream name'));
       });
+
+      testWidgets('navigates to TopicNarrow on tapping topic in ChannelNarrow', (tester) async {
+        final pushedRoutes = <Route<void>>[];
+        final navObserver = TestNavigatorObserver()
+          ..onPushed = (route, prevRoute) => pushedRoutes.add(route);
+        final channel = eg.stream();
+        await setupMessageListPage(tester,
+          narrow: ChannelNarrow(channel.streamId),
+          messages: [eg.streamMessage(stream: channel, topic: 'topic name')],
+          streams: [channel],
+          navObservers: [navObserver]);
+
+        assert(pushedRoutes.length == 1);
+        pushedRoutes.clear();
+
+        connection.prepare(json: eg.newestGetMessagesResult(
+          foundOldest: true, messages: [message]).toJson());
+        await tester.tap(find.descendant(
+          of: find.byType(StreamMessageRecipientHeader),
+          matching: find.text('topic name')));
+        await tester.pumpAndSettle();
+        check(pushedRoutes).single
+          .isA<WidgetRoute>()
+          .page.isA<MessageListPage>()
+          .initNarrow.equals(TopicNarrow(channel.streamId, TopicName('topic name')));
+      });
+
+      testWidgets('does not navigate on tapping topic in TopicNarrow', (tester) async {
+        final pushedRoutes = <Route<void>>[];
+        final navObserver = TestNavigatorObserver()
+          ..onPushed = (route, prevRoute) => pushedRoutes.add(route);
+        final channel = eg.stream();
+        await setupMessageListPage(tester,
+          narrow: TopicNarrow(channel.streamId, TopicName('topic name')),
+          navObservers: [navObserver],
+          streams: [channel],
+          messages: [eg.streamMessage(stream: channel, topic: 'topic name')]);
+
+        assert(pushedRoutes.length == 1);
+        pushedRoutes.clear();
+
+        await tester.tap(find.descendant(
+          of: find.byType(StreamMessageRecipientHeader),
+          matching: find.text('topic name')));
+        await tester.pump();
+        check(pushedRoutes).isEmpty();
+      });
     });
 
     group('DmRecipientHeader', () {