Fix race condition when decrypting notifications during lock disconnection

[bdraco]

Fix race condition when decrypting notifications during lock disconnection

Fixes #353

Problem

A race condition occurs when encrypted notifications arrive during device disconnection:

1. Encrypted command sent to lock
2. Device starts disconnecting (clears IV)
3. Notification arrives with encrypted response
4. _decrypt fails with RuntimeError: Cannot decrypt: IV is None

This timing-dependent issue is hard to reproduce and may vary across Bluetooth stacks.

Solution

Modified _notification_handler in switchbot/devices/lock.py to check the _expected_disconnect flag and skip processing lock notifications during expected disconnection. This prevents the race condition where notifications with encrypted data arrive after the IV has been cleared.

Changes

• Added check in _notification_handler to return early if _expected_disconnect is True
• Logs debug message when ignoring notifications during disconnect
• Prevents _decrypt from being called with None IV during disconnection

Testing

• All existing lock tests pass without modification
• Fix prevents the RuntimeError from occurring during disconnection

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Files with missing lines	Coverage Δ
switchbot/devices/device.py	60.07% <100.00%> (+0.23%)	⬆️
switchbot/devices/lock.py	100.00% <100.00%> (ø)

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[bdraco]

As this return b'', We should add a check in _parse_lock_data to prevent indexError

    def _update_lock_status(self, data: bytearray) -> None:

        lock_data = self._parse_lock_data(self._decrypt(data[4:]), self._model)

        if self._update_parsed_data(lock_data):

            # We leave notifications enabled in case

            # the lock is operated manually before we

            # disconnect.

            self._reset_disconnect_timer()

            self._fire_callbacks()



    @staticmethod

    def _parse_lock_data(data: bytes, model: SwitchbotModel) -> dict[str, Any]:

        if not data:

            return {}

        if model == SwitchbotModel.LOCK:

            return {

                "calibration": bool(data[0] & 0b10000000),

                "status": LockStatus((data[0] & 0b01110000) >> 4),

                "door_open": bool(data[0] & 0b00000100),

                "unclosed_alarm": bool(data[1] & 0b00100000),

                "unlocked_alarm": bool(data[1] & 0b00010000),

            }

You should have access to push to this PR. Feel free to adjust. I won't have time to look soon given it's a holiday in the US

[bdraco]

We could really use a good end to end test framework, but since we don't have one, this will have to do

[bdraco]

I'll do a release

[zerzhang]

I'll do a release

ok, Thanks @bdraco !