fix(ui): let a deleted thread parent with replies take new replies

packages/stream_chat_flutter/CHANGELOG.md

@@ -15,6 +15,7 @@
 
 🐞 Fixed
 
+- Fixed `StreamThreadPage` hiding the composer for a deleted parent message that already has replies, which can still be replied to.
 - Fixed the "Only visible to you" Giphy preview showing a delivery status.
 - Fixed channel list previews showing a "You:" or sender name prefix, and the delivery status, in front of a system message.
 - Fixed a deleted message hiding its replies count, which left its thread unreachable from the channel.

packages/stream_chat_flutter/lib/src/pages/thread_page.dart

@@ -8,7 +8,7 @@ import '../../stream_chat_flutter.dart';
 /// out floating or regular according to the ambient [StreamSurfaceStyle]. Expects a
 /// [StreamChannel] ancestor.
 ///
-/// The composer is omitted when [parent] is deleted.
+/// The composer is omitted when [parent] is deleted and has no replies.
 ///
 /// ## Customizing this page
 ///
@@ -101,7 +101,8 @@ class _StreamThreadPageState extends State<StreamThreadPage> {
       onBackPressed: widget.onBackPressed,
     );
 
-    final composer = !widget.parent.isDeleted
+    final canReply = !widget.parent.isDeleted || (widget.parent.replyCount ?? 0) > 0;
+    final composer = canReply
         ? StreamMessageComposer(
             focusNode: _focusNode,
             messageComposerController: _messageComposerController,
@@ -113,7 +114,7 @@ class _StreamThreadPageState extends State<StreamThreadPage> {
       appBar: appBar,
       bottom: composer,
       // Resolved from the slots so the body inset matches what the chrome draws.
-      // The bottom value is ignored when the composer is null (deleted parent).
+      // The bottom value is ignored when the composer is null.
       appBarSurfaceStyle: StreamThreadHeader.resolveSurfaceStyle(context),
       bottomSurfaceStyle: StreamMessageComposer.resolveSurfaceStyle(context),
       body: _ThreadBody(

packages/stream_chat_flutter/test/src/channel/thread_page_test.dart

@@ -33,14 +33,22 @@ void main() {
     expect(_composerController(tester).message.parentId, 'parent-id');
   });
 
-  testWidgets('hides the composer when the parent message is deleted', (tester) async {
+  testWidgets('hides the composer when the deleted parent message has no replies', (tester) async {
     final parent = Message(id: 'parent-id', text: 'Hello world!', type: 'deleted');
 
     await _pumpThreadPage(tester, parent: parent);
 
     expect(find.byType(StreamMessageComposer), findsNothing);
   });
 
+  testWidgets('shows the composer when the deleted parent message has replies', (tester) async {
+    final parent = Message(id: 'parent-id', text: 'Hello world!', type: 'deleted', replyCount: 1);
+
+    await _pumpThreadPage(tester, parent: parent);
+
+    expect(find.byType(StreamMessageComposer), findsOneWidget);
+  });
+
   testWidgets('still shows the thread when the parent message is deleted', (tester) async {
     final parent = Message(id: 'parent-id', text: 'Hello world!', type: 'deleted');