fix: Http2Adapter does not fail with StateError when connection is closed

[vanelizarov]

Periodically I receive unhandled StateError: Bad state: Cannot add event after closing in Crashlytics:

Stack Trace

StateError: Bad state: Cannot add event after closing
  *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** (***)
  pid: 19891, tid: 483148275864, name 1.ui (unparsed)
  android arch: arm64 comp: yes sim: no (os:)
  build_id: '4f1bdaeddbb49260128a5ff3c1e2e0c4' (unparsed)
  isolate_dso_base: 6ca549c000, vm_dso_base: 6ca549c000 (unparsed)
  isolate_instructions: 6ca5622940, vm_instructions: 6ca560c000 (unparsed)
#0      _StreamController.add (third_party/dart/sdk/lib/async/stream_controller.dart:617:24)
#1      _StreamSinkWrapper.add (third_party/dart/sdk/lib/async/stream_controller.dart:898:13)
#2      Http2Adapter._fetch.<anonymous closure> (/Users/vanelizarov/.pub-cache/git/dio-5259d4ae4fb665b8212c343c015e53fcbfe7d0b7/plugins/http2_adapter/lib/src/http2_adapter.dart:144:33)
#3      _RootZone.runUnaryGuarded (third_party/dart/sdk/lib/async/zone.dart:1778:10)
#4      _BufferingStreamSubscription._sendData (third_party/dart/sdk/lib/async/stream_impl.dart:381:11)
#5      _BufferingStreamSubscription._add (third_party/dart/sdk/lib/async/stream_impl.dart:312:7)
#6      _SinkTransformerStreamSubscription._add (third_party/dart/sdk/lib/async/stream_transformers.dart:67:11)
#7      _EventSinkWrapper.add (third_party/dart/sdk/lib/async/stream_transformers.dart:13:11)
#8      _transform.<anonymous closure> (/Users/vanelizarov/.pub-cache/hosted/pub.dev/dio-5.9.0/lib/src/progress_stream/io_progress_stream.dart:33:16)
#9      _HandlerEventSink.add (third_party/dart/sdk/lib/async/stream_transformers.dart:230:17)
#10     _SinkTransformerStreamSubscription._handleData (third_party/dart/sdk/lib/async/stream_transformers.dart:115:24)
#11     _SinkTransformerStreamSubscription._handleData (third_party/dart/sdk/lib/async/stream_transformers.dart:113:3)
#12     _RootZone.runUnaryGuarded (third_party/dart/sdk/lib/async/zone.dart:1778:10)
#13     _BufferingStreamSubscription._sendData (third_party/dart/sdk/lib/async/stream_impl.dart:381:11)
#14     _BufferingStreamSubscription._add (third_party/dart/sdk/lib/async/stream_impl.dart:312:7)
#15     _MultiStreamController.addSync (third_party/dart/sdk/lib/async/stream_impl.dart:1195:36)
#16     new Stream.fromIterable.<anonymous closure>.next (third_party/dart/sdk/lib/async/stream.dart:385:26)
#17     _microtaskLoop (third_party/dart/sdk/lib/async/schedule_microtask.dart:40:35)
#18     _startMicrotaskLoop (third_party/dart/sdk/lib/async/schedule_microtask.dart:49:5)
#19     _startMicrotaskLoop (third_party/dart/sdk/lib/async/schedule_microtask.dart:44:1)

This problem was mentioned earlier by me in this PR.

After investigation, it appears that the error was caused by a race condition, for example, when the server closed the connection before receiving the request body.

This PR introduces a more reliable way to handle such situations. It also includes a test that can be run with the old implementation to reproduce the described issue.

New Pull Request Checklist

• I have read the Documentation
• I have searched for a similar pull request in the project and found none
• I have updated this branch with the latest main branch to avoid conflicts (via merge from master or rebase)
• I have added the required tests to prove the fix/feature I'm adding
• I have updated the documentation (if necessary)
• I have run the tests without failures
• I have updated the CHANGELOG.md in the corresponding package

[Copilot]

Pull request overview

This PR fixes a race condition in the Http2Adapter that caused unhandled StateError: Bad state: Cannot add event after closing exceptions when the server closes the connection before the client finishes sending the request body.

Key Changes:

• Replaced the simple stream listener with a more robust approach using StreamSubscription, Completer, and explicit error handling to gracefully handle StateError
• Added try-catch block around the final stream.outgoingMessages.close() call to prevent StateError propagation
• Improved cancellation handling by properly cancelling subscriptions before closing streams

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 4 comments.

File	Description
plugins/http2_adapter/lib/src/http2_adapter.dart	Refactored request stream handling to catch StateError during data transmission and gracefully complete the request without propagating the error
plugins/http2_adapter/test/http2_test.dart	Added test case that simulates server closing connection early to verify the StateError fix
plugins/http2_adapter/CHANGELOG.md	Documented the bug fix in the unreleased section
.gitignore	Added .history directory to ignore list

---

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[vanelizarov]

@AlexV525 should I take into account comments from AI or will you do the review manually?

[AlexV525]

@AlexV525 should I take into account comments from AI or will you do the review manually?

@vanelizarov AI might give helpful suggestions. If you have opposite opinions, you can leave comments saying that you disagree with the suggestion. A manual review will be sent eventually, before the PR is merged.

Additionally, the suggestions in the above review seem reasonable.

[github-actions]

Code Coverage Report: Only Changed Files listed

Package	Base Coverage	New Coverage	Difference
plugins/http2_adapter/lib/src/connection_manager_imp.dart	🟢 78.83%	🟢 83.94%	🟢 5.11%
plugins/http2_adapter/lib/src/http2_adapter.dart	🟠 74.13%	🟢 78.48%	🟢 4.35%
Overall Coverage	🟢 87.95%	🟢 88.58%	🟢 0.63%

Minimum allowed coverage is 0%, this run produced 88.58%

[AlexV525]

I'm still not confident about shipping this implementation, given that we didn't find the root cause here. Could you share a reproducible case in production?

[AlexV525]

This seems redundant.

[AlexV525]

It would be better if you could submit a separate PR for this with more context.