Отладчик: обрыв соединения, работающие потоки и watch-выражения

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Несколько проблем отладчика, которые всплыли при отладке скриптов с фоновыми заданиями и при обрывах связи:

• клиент, который подключился и закрылся до рукопожатия (проверка порта, IDE убили при подключении), ронял отлаживаемый процесс необработанным IOException в потоке приема подключений — для -debug -noWait сервиса это падение сервиса. Теперь ошибка на одном клиенте закрывает только его, а у рукопожатия таймаут;
• если IDE пропала без Disconnect, JsonDtoChannel.Read отдавал EOF как некритичную ошибку, и цикл сообщений крутил чтение на 100% CPU, сессия оставалась активной (новые клиенты отвергались), остановленные потоки висели. Теперь обрыв — критичная ошибка канала, сессия закрывается и отпускает потоки; в launch-режиме скрипт, не дождавшийся Execute, выполняется без отладчика, а не ждет вечно;
• Continue в VSCode отпускает все потоки, в том числе тот, о чьей остановке IDE еще не знает, и потом IDE читает стек и вычисляет выражения на работающем потоке (Stack empty, неверные результаты). Стек, переменные и шаги теперь только для остановленного потока, иначе ошибка;
• watch-выражение, вызывающее метод скрипта, выполнялось в потоке сообщений отладчика: взяв блокировку, которую держит остановленный поток, или попав на точку останова, оно вешало отладчик. Теперь выражение выполняется в самом остановленном потоке, точки останова внутри него пропускаются;
• JsonDtoChannel.Write пишут и поток сообщений, и потоки скриптов — теперь сообщение целиком под блокировкой; отключение отладчика в момент остановки потока больше не бросает ObjectDisposedException/ArgumentOutOfRangeException в скрипт.

Тесты DebuggerConnectionTests и DebuggerEvaluationTests в DebugProtocol.Test.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Debugger sessions now shut down cleanly when a client disconnects, including before execution begins.
  • Watch expressions and other debugger operations now run on the appropriate stopped thread; requests for running threads are rejected.
  • Thread stop and resume events are handled more reliably, including when a stop event and continue command occur together.
  • Concurrent debugger messages no longer get mixed together.
  • Connection failures and closed channels are handled without interrupting the server.
  • Debugger connections that do not complete the initial handshake time out, preventing indefinite waits.

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Run ID: 5fd43a8f-ef8a-459d-81d3-dd4623a08b99

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Reviewing files that changed from the base of the PR and between 9854fda and 2640c70.

📒 Files selected for processing (2)

• src/OneScript.DebugProtocol/TcpServer/DefaultMessageServer.cs
• src/Tests/OneScript.DebugProtocol.Test/DebuggerConnectionTests.cs

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📝 Walkthrough

Walkthrough

Debugger connection handling now includes handshake timeouts, serialized message writes, and session cleanup on channel closure. Debugger operations use stopped-thread tokens to run queued evaluation work on the machine thread. New tests cover connection lifecycle, token behavior, concurrent writes, and evaluation.

Changes

Debugger runtime

Layer / File(s)	Summary
Transport and connection setup src/OneScript.DebugProtocol/TcpServer/DefaultMessageServer.cs, src/OneScript.DebugProtocol/TcpServer/JsonDtoChannel.cs, src/OneScript.DebugServices/DefaultDebugger.cs, src/OneScript.DebugServices/Internal/TcpEventCallbackChannel.cs, src/OneScript.DebugServices/TcpDebugServer.cs, src/Tests/OneScript.DebugProtocol.Test/DebuggerConnectionTests.cs, src/Tests/OneScript.DebugProtocol.Test/Tools/TestDebuggerClient.cs	The message server reports critical channel errors before stopping and avoids interrupting its own message thread. The channel serializes writes and reports closed-channel reads. The debugger applies a handshake timeout, and the TCP server handles listener shutdown and client setup exceptions. Tests cover connection handling and concurrent writes, and add client close and read helpers.
Session and thread lifecycle src/OneScript.DebugServices/Internal/DebugSession.cs, src/OneScript.DebugServices/MachineWaitToken.cs, src/OneScript.DebugServices/ThreadManager.cs, src/Tests/OneScript.DebugProtocol.Test/DebuggerConnectionTests.cs	Sessions dispose once on channel closure and release startup waiters. MachineWaitToken queues work while stopped and wakes waiters on release. ThreadManager skips stop events for unregistered threads. Tests cover disconnects and token behavior.
Debugger operations on stopped threads src/OneScript.DebugServices/Internal/DebuggerServiceImpl.cs, src/Tests/OneScript.DebugProtocol.Test/DebuggerEvaluationTests.cs	Stack-frame, evaluation, and stepping operations require stopped-thread tokens. Evaluation runs on the stopped machine thread. Tests cover evaluation on a stopped thread.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant DebuggerRPCClient
  participant DebuggerServiceImpl
  participant MachineWaitToken
  participant MachineThread
  DebuggerRPCClient->>DebuggerServiceImpl: Send evaluation request
  DebuggerServiceImpl->>MachineWaitToken: RunOnStoppedThread
  MachineWaitToken->>MachineThread: Run queued evaluation
  MachineThread-->>MachineWaitToken: Return evaluation result
  MachineWaitToken-->>DebuggerServiceImpl: Return result
  DebuggerServiceImpl-->>DebuggerRPCClient: Return RPC result

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Merge Risk: ⚪ Minimal · up to 2640c

The connection-loss cleanup defect is corrected, and the supplied evidence identifies no remaining merge-blocking issue. The change is ready to merge subject to normal checks.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 2640c

The changes improve disconnect handling and constrain debugger operations to stopped threads without establishing broader access or additional privileges. Remaining uncertainty concerns work already accepted during shutdown and deployment-specific exposure.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — A peer admitted to the debugger can affect the debugged process and its registered script threads through evaluation and execution control. The reviewed changes do not establish cross-service or cross-tenant expansion; remote reachability and access to external assets depend on unavailable deployment controls and script capabilities.

Trust Boundaries and Controls

• observed — Protocol admission remains before session construction. After admission, evaluation obtains the session-owned target token and checks its stopped state again at enqueue time. The supplied TCP listener invokes connection admission synchronously on its listener thread.

Resilience and Maintainability Implications

• observed — Released tokens cannot be stopped again through Reset, and new work is rejected once their stopped state is cleared. Already-queued work is not cancelled: Wait drains it even after release, while the caller waits synchronously for completion. Release therefore is not a cancellation guarantee for accepted evaluation.

Hardening Proposals

• proposed — Make the terminal-state contract explicit for accepted evaluation: whether release drains or cancels pending work, how running work completes, and how interruption preserves completion-object lifetime. Validate those interleavings before treating session release as a bounded recovery guarantee.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 15.09% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 53 functions across 12 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	Заголовок точно отражает основные изменения: обработку обрыва соединения, работу с потоками и выполнение watch-выражений.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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Inline comments:
Review comments at
@src/OneScript.DebugProtocol/TcpServer/DefaultMessageServer.cs:
- Around line 62-64: Update DefaultMessageServer.Stop so it does not interrupt
the message thread when Stop is called from that same thread; retain the
existing interrupt behavior when Stop is called from another thread.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: 0387f565-025c-43f7-8e75-10453c02b8a6

📥 Commits

Reviewing files that changed from the base of the PR and between 36e2ca9 and 9854fda.

📒 Files selected for processing (12)

• src/OneScript.DebugProtocol/TcpServer/DefaultMessageServer.cs
• src/OneScript.DebugProtocol/TcpServer/JsonDtoChannel.cs
• src/OneScript.DebugServices/DefaultDebugger.cs
• src/OneScript.DebugServices/Internal/DebugSession.cs
• src/OneScript.DebugServices/Internal/DebuggerServiceImpl.cs
• src/OneScript.DebugServices/Internal/TcpEventCallbackChannel.cs
• src/OneScript.DebugServices/MachineWaitToken.cs
• src/OneScript.DebugServices/TcpDebugServer.cs
• src/OneScript.DebugServices/ThreadManager.cs
• src/Tests/OneScript.DebugProtocol.Test/DebuggerConnectionTests.cs
• src/Tests/OneScript.DebugProtocol.Test/DebuggerEvaluationTests.cs
• src/Tests/OneScript.DebugProtocol.Test/Tools/TestDebuggerClient.cs

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