feat(ui, core): add maybeOf methods for safe context access (#2315)

Co-authored-by: itsmeadi <[email protected]>

Author: xsahil03x

packages/stream_chat_flutter/CHANGELOG.md

@@ -1,3 +1,14 @@
+## Upcoming
+
+✅ Added
+
+- Added `StreamChat.maybeOf()` method for safe context access in async operations.
+
+🐞 Fixed
+
+- Fixed `StreamMessageInput` crashes with "Null check operator used on a null value" when async
+  operations continue after widget unmounting.
+
 ## 9.14.0
 
 🐞 Fixed

packages/stream_chat_flutter/lib/src/message_input/stream_message_input.dart

@@ -946,39 +946,36 @@ class StreamMessageInputState extends State<StreamMessageInput>
         defaultButton;
   }
 
-  Future<void> _sendPoll(Poll poll) {
-    final streamChannel = StreamChannel.of(context);
-    final channel = streamChannel.channel;
-
+  Future<void> _sendPoll(Poll poll, Channel channel) {
     return channel.sendPoll(poll);
   }
 
-  Future<void> _updatePoll(Poll poll) {
-    final streamChannel = StreamChannel.of(context);
-    final channel = streamChannel.channel;
-
+  Future<void> _updatePoll(Poll poll, Channel channel) {
     return channel.updatePoll(poll);
   }
 
-  Future<void> _deletePoll(Poll poll) {
-    final streamChannel = StreamChannel.of(context);
-    final channel = streamChannel.channel;
-
+  Future<void> _deletePoll(Poll poll, Channel channel) {
     return channel.deletePoll(poll);
   }
 
-  Future<void> _createOrUpdatePoll(Poll? old, Poll? current) async {
+  Future<void> _createOrUpdatePoll(
+    Poll? old,
+    Poll? current,
+  ) async {
+    final channel = StreamChannel.maybeOf(context)?.channel;
+    if (channel == null) return;
+
     // If both are null or the same, return
     if ((old == null && current == null) || old == current) return;
 
     // If old is null, i.e., there was no poll before, create the poll.
-    if (old == null) return _sendPoll(current!);
+    if (old == null) return _sendPoll(current!, channel);
 
     // If current is null, i.e., the poll is removed, delete the poll.
-    if (current == null) return _deletePoll(old);
+    if (current == null) return _deletePoll(old, channel);
 
     // Otherwise, update the poll.
-    return _updatePoll(current);
+    return _updatePoll(current, channel);
   }
 
   /// Handle the platform-specific logic for selecting files.
@@ -996,7 +993,10 @@ class StreamMessageInputState extends State<StreamMessageInput>
       ..removeWhere((it) {
         if (it != AttachmentPickerType.poll) return false;
         if (_effectiveController.message.parentId != null) return true;
-        final channel = StreamChannel.of(context).channel;
+
+        final channel = StreamChannel.maybeOf(context)?.channel;
+        if (channel == null) return true;
+
         if (channel.config?.polls == true && channel.canSendPoll) return false;
 
         return true;
@@ -1210,11 +1210,12 @@ class StreamMessageInputState extends State<StreamMessageInput>
 
   late final _onChangedDebounced = debounce(
     () {
-      var value = _effectiveController.text;
       if (!mounted) return;
-      value = value.trim();
 
-      final channel = StreamChannel.of(context).channel;
+      final channel = StreamChannel.maybeOf(context)?.channel;
+      if (channel == null) return;
+
+      final value = _effectiveController.text.trim();
       if (value.isNotEmpty && channel.canSendTypingEvents) {
         // Notify the server that the user started typing.
         channel.keyStroke(_effectiveController.message.parentId).onError(
@@ -1235,7 +1236,7 @@ class StreamMessageInputState extends State<StreamMessageInput>
 
       setState(() => _actionsShrunk = value.isNotEmpty && actionsLength > 1);
 
-      _checkContainsUrl(value, context);
+      _checkContainsUrl(value, channel);
     },
     const Duration(milliseconds: 350),
     leading: true,
@@ -1264,7 +1265,7 @@ class StreamMessageInputState extends State<StreamMessageInput>
     caseSensitive: false,
   );
 
-  void _checkContainsUrl(String value, BuildContext context) async {
+  void _checkContainsUrl(String value, Channel channel) async {
     // Cancel the previous operation if it's still running
     _enrichUrlOperation?.cancel();
 
@@ -1281,10 +1282,8 @@ class StreamMessageInputState extends State<StreamMessageInput>
     }).toList();
 
     // Reset the og attachment if the text doesn't contain any url
-    if (matchedUrls.isEmpty ||
-        !StreamChannel.of(context).channel.canSendLinks) {
-      _effectiveController.clearOGAttachment();
-      return;
+    if (matchedUrls.isEmpty || !channel.canSendLinks) {
+      return _effectiveController.clearOGAttachment();
     }
 
     final firstMatchedUrl = matchedUrls.first.group(0)!;
@@ -1294,7 +1293,8 @@ class StreamMessageInputState extends State<StreamMessageInput>
       return;
     }
 
-    final client = StreamChat.of(context).client;
+    final client = StreamChat.maybeOf(context)?.client;
+    if (client == null) return;
 
     _enrichUrlOperation = CancelableOperation.fromFuture(
       _enrichUrl(firstMatchedUrl, client),
@@ -1319,7 +1319,6 @@ class StreamMessageInputState extends State<StreamMessageInput>
   ) async {
     var response = _ogAttachmentCache[url];
     if (response == null) {
-      final client = StreamChat.of(context).client;
       try {
         response = await client.enrichUrl(url);
         _ogAttachmentCache[url] = response;
@@ -1462,7 +1461,9 @@ class StreamMessageInputState extends State<StreamMessageInput>
     if (_effectiveController.isSlowModeActive) return;
     if (!widget.validator(_effectiveController.message)) return;
 
-    final streamChannel = StreamChannel.of(context);
+    final streamChannel = StreamChannel.maybeOf(context);
+    if (streamChannel == null) return;
+
     final channel = streamChannel.channel;
     var message = _effectiveController.value;
 
@@ -1483,7 +1484,7 @@ class StreamMessageInputState extends State<StreamMessageInput>
       return;
     }
 
-    _maybeDeleteDraftMessage(message);
+    _maybeDeleteDraftMessage(message, channel);
     widget.onQuotedMessageCleared?.call();
     _effectiveController.reset();
 
@@ -1501,7 +1502,7 @@ class StreamMessageInputState extends State<StreamMessageInput>
       await WidgetsBinding.instance.endOfFrame;
     }
 
-    await _sendOrUpdateMessage(message: message);
+    await _sendOrUpdateMessage(message: message, channel: channel);
 
     if (mounted) {
       if (widget.shouldKeepFocusAfterMessage ?? !_commandEnabled) {
@@ -1514,10 +1515,9 @@ class StreamMessageInputState extends State<StreamMessageInput>
 
   Future<void> _sendOrUpdateMessage({
     required Message message,
+    required Channel channel,
   }) async {
     try {
-      final channel = StreamChannel.of(context).channel;
-
       // Note: edited messages which are bounced back with an error needs to be
       // sent as new messages as the backend doesn't store them.
       final resp = await switch (_isEditing && !message.isBouncedWithError) {
@@ -1558,19 +1558,21 @@ class StreamMessageInputState extends State<StreamMessageInput>
   }
 
   void _maybeUpdateOrDeleteDraftMessage() {
+    final channel = StreamChannel.maybeOf(context)?.channel;
+    if (channel == null) return;
+
     final message = _effectiveController.message;
     final isMessageValid = widget.validator.call(message);
 
     // If the message is valid, we need to create or update it as a draft
     // message for the channel or thread.
-    if (isMessageValid) return _maybeUpdateDraftMessage(message);
+    if (isMessageValid) return _maybeUpdateDraftMessage(message, channel);
 
     // Otherwise, we need to delete the draft message.
-    return _maybeDeleteDraftMessage(message);
+    return _maybeDeleteDraftMessage(message, channel);
   }
 
-  void _maybeUpdateDraftMessage(Message message) {
-    final channel = StreamChannel.of(context).channel;
+  void _maybeUpdateDraftMessage(Message message, Channel channel) {
     final draft = switch (message.parentId) {
       final parentId? => channel.state?.threadDraft(parentId),
       null => channel.state?.draft,
@@ -1584,8 +1586,7 @@ class StreamMessageInputState extends State<StreamMessageInput>
     return channel.createDraft(draftMessage).ignore();
   }
 
-  void _maybeDeleteDraftMessage(Message message) {
-    final channel = StreamChannel.of(context).channel;
+  void _maybeDeleteDraftMessage(Message message, Channel channel) {
     final draft = switch (message.parentId) {
       final parentId? => channel.state?.threadDraft(parentId),
       null => channel.state?.draft,

packages/stream_chat_flutter/lib/src/stream_chat.dart

@@ -71,19 +71,67 @@ class StreamChat extends StatefulWidget {
   @override
   StreamChatState createState() => StreamChatState();
 
-  /// Use this method to get the current [StreamChatState] instance
+  /// Finds the [StreamChatState] from the closest [StreamChat] ancestor
+  /// that encloses the given [context].
+  ///
+  /// This will throw a [FlutterError] if no [StreamChat] is found in the
+  /// widget tree above the given context.
+  ///
+  /// Typical usage:
+  ///
+  /// ```dart
+  /// final chatState = StreamChat.of(context);
+  /// ```
+  ///
+  /// If you're calling this in the same `build()` method that creates the
+  /// `StreamChat`, consider using a `Builder` or refactoring into a
+  /// separate widget to obtain a context below the [StreamChat].
+  ///
+  /// If you want to return null instead of throwing, use [maybeOf].
   static StreamChatState of(BuildContext context) {
-    StreamChatState? streamChatState;
+    final result = maybeOf(context);
+    if (result != null) return result;
 
-    streamChatState = context.findAncestorStateOfType<StreamChatState>();
-
-    if (streamChatState == null) {
-      throw Exception(
-        'You must have a StreamChat widget at the top of your widget tree',
-      );
-    }
+    throw FlutterError.fromParts(<DiagnosticsNode>[
+      ErrorSummary(
+        'StreamChat.of() called with a context that does not contain a '
+        'StreamChat.',
+      ),
+      ErrorDescription(
+        'No StreamChat ancestor could be found starting from the context '
+        'that was passed to StreamChat.of(). This usually happens when the '
+        'context used comes from the widget that creates the StreamChat '
+        'itself.',
+      ),
+      ErrorHint(
+        'To fix this, ensure that you are using a context that is a descendant '
+        'of the StreamChat. You can use a Builder to get a new context that '
+        'is under the StreamChat:\n\n'
+        '  Builder(\n'
+        '    builder: (context) {\n'
+        '      final chatState = StreamChat.of(context);\n'
+        '      ...\n'
+        '    },\n'
+        '  )',
+      ),
+      ErrorHint(
+        'Alternatively, split your build method into smaller widgets so that '
+        'you get a new BuildContext that is below the StreamChat in the '
+        'widget tree.',
+      ),
+      context.describeElement('The context used was'),
+    ]);
+  }
 
-    return streamChatState;
+  /// Finds the [StreamChatState] from the closest [StreamChat] ancestor
+  /// that encloses the given context.
+  ///
+  /// Returns null if no such ancestor exists.
+  ///
+  /// See also:
+  ///  * [of], which throws if no [StreamChat] is found.
+  static StreamChatState? maybeOf(BuildContext context) {
+    return context.findAncestorStateOfType<StreamChatState>();
   }
 }