fix(stdio): handle ObjectDisposedException from disposed NetworkStream during domain reload

[beast-ofcourse]

Problem

After domain reload or compilation, StdioBridgeHost logs an error: Cannot access a disposed object. Object name: 'System.Net.Sockets.NetworkStream'. While the HandleClientAsync outer catch already treats ObjectDisposedException as benign, the I/O methods (ReadExactAsync, WriteFrameAsync) throw it raw, making the code depend on a single catch block for correctness.

Fixes #1232

Root Cause

During domain reload, Stop() closes all active TcpClient connections via c.Close(). Any pending async read/write on the underlying NetworkStream throws ObjectDisposedException. While this is caught and treated as benign at the HandleClientAsync outer catch, the exception type is inconsistent — ReadExactAsync and WriteFrameAsync throw ObjectDisposedException while every other connection-closed scenario throws IOException.

Solution

Two defensive changes at the I/O boundary:

1. ReadExactAsync: Added catch (ObjectDisposedException) that throws IOException("Connection closed before reading expected bytes") — matching the existing pattern when stream.ReadAsync returns 0 bytes.

2. WriteFrameAsync: Wrapped the WriteAsync calls in a try/catch that converts ObjectDisposedException to IOException("Connection closed before writing frame").

This follows the standard .NET pattern where disposed network resources throw IOException rather than ObjectDisposedException, and ensures consistent handling at every level of the stack.

Verification

• The existing top-level benign check (|| ex is IOException) now catches disposed-stream scenarios uniformly — previously it only caught ObjectDisposedException which was fragile.
• Read and write paths are both covered.
• No behavioral change during normal operation — only the exception type changes during shutdown races.

Notes

• The WriteFrameAsync try/catch adds a small indentation change for the preprocessor conditional body, but no logic changes beyond the new catch block.

Summary by CodeRabbit

• Bug Fixes
  • Improved error handling when a connection closes unexpectedly during read or write operations.
  • Read failures now report a clearer I/O error if the expected data cannot be received.
  • Write failures now report a clearer I/O error if a frame cannot be fully sent before the connection closes.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 7d9861eb-f44e-4305-8d73-fe93995609f2

📥 Commits

Reviewing files that changed from the base of the PR and between 484937c and 7d25ce1.

📒 Files selected for processing (1)

• MCPForUnity/Editor/Services/Transport/Transports/StdioBridgeHost.cs

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📝 Walkthrough

Walkthrough

ReadExactAsync and WriteFrameAsync in StdioBridgeHost.cs now catch ObjectDisposedException and rethrow it as an IOException with a descriptive message, rather than letting the disposal exception propagate directly.

Changes

Disposed Connection Error Handling

Layer / File(s)	Summary
Convert disposed-stream exceptions to IOException MCPForUnity/Editor/Services/Transport/Transports/StdioBridgeHost.cs	ReadExactAsync and WriteFrameAsync now catch ObjectDisposedException and rethrow it as an IOException describing that the connection closed before the read/write completed.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Possibly related PRs

• CoplayDev/unity-mcp#1198: Also modifies StdioBridgeHost.cs to treat ObjectDisposedException as a benign/IO condition during connection teardown.

Suggested labels: bug, transport

Suggested reviewers: none

🐰 A stream once closed, an object gone,
Now wrapped in IOException, calmly drawn,
No more disposed errors loudly cried,
Just a tidy message when connections have died.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is concise and accurately summarizes the disposed-NetworkStream fix during domain reload.
Description check	✅ Passed	The description explains the bug, root cause, fix, and verification, but omits several template sections like type, compatibility, and testing.
Linked Issues check	✅ Passed	The code normalizes disposed NetworkStream failures to IOException in both read and write paths, matching the issue's shutdown-race fix.
Out of Scope Changes check	✅ Passed	The changes stay within StdioBridgeHost and only address disposed-stream handling; no unrelated edits are indicated.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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