fix(web-incoming): emit econnreset on client disconnect

[pi0]

Summary

• Fix race condition where client disconnect ECONNRESET errors were incorrectly routed to the error event instead of econnreset
• Replace req.socket.destroyed check with !req.socket?.writable which is set earlier during socket teardown
• Add regression test that simulates the race (socket non-writable but not yet destroyed)

Upstream ref: http-party/node-http-proxy#1542

Detail

The createErrorHandler in web-incoming.ts checks whether an ECONNRESET error is caused by a client disconnect. The original check (req.socket.destroyed) can be false during a timing race where the socket is closing but not yet fully destroyed. The upstream fix used req.aborted, but that property is deprecated since Node.js 17.

This fix uses !req.socket?.writable instead, which:

• Is false when the client has disconnected (socket closing/closed)
• Is true when the client is still connected (e.g. proxy timeout)
• Works reliably across modern Node.js versions
• Also handles the edge case where req.socket is null via optional chaining

Test plan

• New regression test reproduces the race condition and verifies econnreset event fires
• Existing proxyTimeout test still passes (timeout ECONNRESET correctly goes to error event)
• Full test suite passes (229 tests)

Summary by CodeRabbit

• Bug Fixes

  • Enhanced detection and handling of connection reset errors to improve proxy reliability and error reporting.

• Tests

  • Added test coverage for client disconnect race conditions to ensure proper event emission during connection failures.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 74e1aa67-3940-42f3-9c2f-62ab7bbb3c63

📥 Commits

Reviewing files that changed from the base of the PR and between b7075ab and b12a68f.

📒 Files selected for processing (2)

• src/middleware/web-incoming.ts
• test/http-proxy.test.ts

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📝 Walkthrough

Walkthrough

The ECONNRESET error handling in the stream proxy middleware was updated to check socket writability instead of destruction status. When connection reset occurs with a non-writable socket, the middleware emits an econnreset event. A test case validates this behavior under client disconnect race conditions.

Changes

Cohort / File(s)	Summary
Error Handling Logic src/middleware/web-incoming.ts	Modified ECONNRESET condition from checking req.socket?.destroyed to !req.socket?.writable. When true, the middleware now emits server.emit("econnreset", ...) and destroys proxyReq.
Test Coverage test/http-proxy.test.ts	Added new test case under client disconnect that simulates a race condition by intercepting proxyReq event, toggling socket state (writable to false, destroyed to false), emitting ECONNRESET error, and asserting econnreset event emission.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Poem

🐰 A socket's writable state, now we test with care,
Race conditions caught before they snare,
One line changed, but logic refined,
To handle resets with peace of mind! 🔌✨

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/client-disconnect-error

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.11%. Comparing base (b7075ab) to head (b12a68f).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #115   +/-   ##
=======================================
  Coverage   96.11%   96.11%           
=======================================
  Files           8        8           
  Lines         644      644           
  Branches      244      244           
=======================================
  Hits          619      619           
  Misses         24       24           
  Partials        1        1           

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