Propagate timeout through SOCKS5 handshake

[mbeijen]

Summary

During SOCKS5 connection setup, all reads and writes to the proxy socket were called without a timeout. A non-responsive SOCKS5 proxy (one that accepts the TCP connection but never sends a handshake reply) would block the calling thread/task indefinitely, regardless of any timeout configured on the request.

This PR threads the connect timeout (already used for the initial TCP connect) through _init_socks5_connection() to every stream.read() / stream.write() call during auth method negotiation, optional username/password auth, and the SOCKS5 CONNECT request.

Ports encode/httpcore#1055 (drshvik), via codeberg.org/httpxyz/httpcorexyz@0387930.

Notes

• Only _async/socks_proxy.py was edited by hand; _sync/socks_proxy.py was regenerated by scripts/unasync.py.
• Neither the upstream PR nor the fork commit added a dedicated unit test (the upstream PR ships reproduction scripts instead — a real-hang test needs an integration-style fixture). The existing MockBackend-based SOCKS5 tests already exercise the new code path with timeout=None. 100% coverage is preserved.

---

Note: this change was prepared with AI assistance (Claude Code).

[codspeed-hq]

Merging this PR will not alter performance

✅ 15 untouched benchmarks
⏩ 7 skipped benchmarks¹

---

_{Comparing mbeijen:fix/socks5-handshake-timeout (f5a995d) with main (04f3804)}

Footnotes

1. 7 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[cubic-dev-ai]

No issues found across 2 files

_{Re-trigger cubic}

[Kludex]

This doesn't seem correct, is it? We are using the connect timeout for everything.

I think before addressing this we need to make httpcore2 a bit more type safe in the Extensions type - maybe starting by splitting it in RequestExtensions and ResponseExtensions.

[mbeijen]

I think before addressing this we need to make httpcore2 a bit more type safe in the Extensions type - maybe starting by splitting it in RequestExtensions and ResponseExtensions.

That's reasonable! Do you pick that up or would you like me to create a PR?

[Kludex]

You can do it. You'll probably need extra_items and total=False, so we probably need to include typing extensions.

Change httpcore2 only if possible.