fix: prevent adding events to closed StreamController

[rwrz]

Add isClosed checks to DataStreamController's write() and error() methods to prevent "Bad state: Cannot add event after closing" exception.

This error occurs when a participant disconnects and validateParticipantHasNoActiveDataStreams() tries to send errors to stream controllers that have already been closed.

Summary by CodeRabbit

• Bug Fixes
  • Improved stability by preventing errors when operations are attempted on closed data streams. The system now gracefully handles edge cases where write or error operations occur after stream closure, ensuring more reliable behavior without throwing exceptions.

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[coderabbitai]

📝 Walkthrough

Walkthrough

The DataStreamController's write() and error() methods now include guards that check if the underlying StreamController is closed before attempting to add chunks or errors, preventing operations on closed controllers.

Changes

Cohort / File(s)	Summary
Defensive Checks for Closed Stream Controller lib/src/types/data_stream.dart	Added isClosed guards in write() and error() methods to prevent operations when the underlying StreamController is closed, replacing unconditional add/addError calls that could throw.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Poem

🐰 A guardian checks before it leaps,
No write shall wake what deeply sleeps,
The stream controller's door now sealed tight,
With gentle guards we've set things right! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: adding guards in DataStreamController to prevent operations on closed StreamControllers.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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🧹 Recent nitpick comments

lib/src/types/data_stream.dart (1)

164-174: The fix correctly prevents the exception, but consider adding observability for dropped writes/errors.

The isClosed guards effectively prevent the "Bad state" exception. However, silently discarding chunks and errors could make debugging harder in edge cases where writes are unexpectedly dropped.

Consider one of these optional improvements:

1. Add debug-level logging when a write/error is ignored
2. Return a bool to indicate success (though this would be a breaking change)
3. Document the silent-drop behavior in doc comments

♻️ Optional: Add logging for dropped writes

+import 'package:logging/logging.dart';
+
+final _logger = Logger('DataStreamController');
+
 void write(T chunk) {
-   if (!streamController.isClosed) {
+   if (streamController.isClosed) {
+     _logger.fine('Ignoring write to closed stream: ${info.id}');
+     return;
+   }
-     streamController.add(chunk);
-   }
+   streamController.add(chunk);
 }

 void error(DataStreamError error) {
-   if (!streamController.isClosed) {
+   if (streamController.isClosed) {
+     _logger.fine('Ignoring error on closed stream: ${info.id}');
+     return;
+   }
-     streamController.addError(error);
-   }
+   streamController.addError(error);
 }

📜 Recent review details

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 57c8d42 and 2eaf998.

📒 Files selected for processing (1)

• lib/src/types/data_stream.dart

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