Fix WebSocket handshake failure for chargers missing Connection: Upgrade header

[vavallee]

Problem

Some charger firmware (e.g. Autel MaxiCharger US AC LW10-N14, fw v1.38.00/v1.22.00) omits the required Connection: Upgrade header from the WebSocket opening handshake. websockets 14+ strictly validates this header and raises InvalidUpgrade, so the affected chargers can never connect to the OCPP central system.

Fix

Add a process_request hook (_fix_missing_connection_header) that injects Connection: upgrade before the library validates the handshake, only when the header is absent. Logs a warning recommending a firmware update. No effect on compliant chargers (covered by a test asserting no warning is logged when the header is present).

Notes

• Rebased onto v0.10.15; api.py is otherwise unchanged in that range so this applies cleanly.
• Module-level function + unit tests in tests/test_api_paths.py.
• Supersedes Fix WebSocket handshake failure for chargers missing Connection: Upgrade header #1933, which was auto-closed by the stale bot without a human review — not on technical grounds. Friendly ping @lbbrhzn for a look when you have a moment; happy to adjust.

Summary by CodeRabbit

• Bug Fixes
  • Improved WebSocket connection handling for chargers with firmware that omits the required upgrade header.
  • Connection attempts that previously failed during the initial handshake should now proceed more reliably.
  • Added safeguards to preserve valid connection headers when they are already present.

[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: 4827b755-9caf-4032-9554-38037ffa002f

📥 Commits

Reviewing files that changed from the base of the PR and between c61c1f4 and 9c709a6.

📒 Files selected for processing (2)

• custom_components/ocpp/api.py
• tests/test_api_paths.py

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📝 Walkthrough

Walkthrough

Adds _fix_missing_connection_header, a process_request callback that detects missing Connection headers in WebSocket upgrade requests, logs a warning, and injects Connection: upgrade before validation. This callback is wired into websockets.serve. Two new async tests cover the injection and no-op paths.

Changes

WebSocket Connection header workaround

Layer / File(s)	Summary
Header injection callback and server wiring custom_components/ocpp/api.py	Imports Request/Response from websockets.http11, defines _fix_missing_connection_header to detect absent Connection headers, log a warning, and mutate headers to set Connection: upgrade, then wires it into websockets.serve via process_request.
Tests for injection and no-op tests/test_api_paths.py	Adds _fix_missing_connection_header to test imports and introduces two async tests: one asserting warning emission and header injection when Connection is missing, one asserting no mutation and no warning when it is present.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐇 A header went missing, the handshake would fail,
So I twitched my nose and injected the trail.
"Connection: upgrade!" I whispered with care,
The websocket opened — no error to bear.
Two tests to confirm it, all passing with glee! 🌿

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: a WebSocket handshake fix for chargers missing the Connection: Upgrade header.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
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.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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