actions: Omit 'Mark as unread' for messages in unsubscribed streams.

earlier, the 'Mark as unread' button was displayed for any read message even if they were unsubscribed .

This pr change adds a condition that should only show the button for direct messages or for stream messages where the subscription exists. The corresponding test is added to verify this new behavior which uses the `setupToMessageActionSheet` helper, dismissing the action sheet and also firing the `SubscriptionRemoveEvent`, and then re-opening the sheet to confirm that the button is now  not present there

Author: loveucifer

lib/widgets/action_sheet.dart

@@ -607,7 +607,7 @@ void showMessageActionSheet({required BuildContext context, required Message mes
   final isMessageRead = message.flags.contains(MessageFlag.read);
   final markAsUnreadSupported = store.zulipFeatureLevel >= 155; // TODO(server-6)
   final showMarkAsUnreadButton = markAsUnreadSupported && isMessageRead &&
-  (message is! StreamMessage || store.subscriptions[message.streamId] != null);
+    (message is! StreamMessage || store.subscriptions[message.streamId] != null);
 
   final isSenderMuted = store.isUserMuted(message.senderId);
 

test/widgets/action_sheet_test.dart

@@ -1341,6 +1341,38 @@ void main() {
         check(find.byIcon(Icons.mark_chat_unread_outlined).evaluate()).single;
       });
 
+      testWidgets('not visible if message is in unsubscribed stream', (tester) async {
+        // Setup with a read message, so the button is potentially visible.
+        final readMessage = eg.streamMessage(flags: [MessageFlag.read]);
+
+        // this will use the common helper function .
+        // This will subscribe to the stream and open the action sheet .
+        await setupToMessageActionSheet(tester,
+          message: readMessage, narrow: TopicNarrow.ofMessage(readMessage));
+
+        // Initially, the button should be visible because the helper subscribes to the stream.
+        check(find.byIcon(Icons.mark_chat_unread_outlined).evaluate()).single;
+
+        // Close the action sheet
+        await tester.tapAt(const Offset(0, 0)); // Tap outside to dismiss it
+        await tester.pumpAndSettle();
+
+        // Now, we will fire an event to unsubscribe from the stream.
+        await store.handleEvent(SubscriptionRemoveEvent(
+          id: 999, // dummy event ID
+          streamIds: [readMessage.streamId]));
+
+        // this will Process the state change
+        await tester.pump();
+
+        // Open the action sheet again after unsubscribing from the stream
+        await tester.longPress(find.byType(MessageContent), warnIfMissed: false);
+        await tester.pump(const Duration(milliseconds: 250));
+
+        // After the rebuild, the button should be gone.
+        check(find.byIcon(Icons.mark_chat_unread_outlined).evaluate()).isEmpty();
+      });
+
       group('onPressed', () {
         testWidgets('smoke test', (tester) async {
           final message = eg.streamMessage(flags: [MessageFlag.read]);
@@ -1547,7 +1579,6 @@ void main() {
           of: find.byWidget(snackbar.content),
           matching: find.text(zulipLocalizations.successMessageTextCopied)));
       });
-
       testWidgets('request has an error', (tester) async {
         final message = eg.streamMessage();
         await setupToMessageActionSheet(tester, message: message, narrow: TopicNarrow.ofMessage(message));