Fix reading the display on a SKY

[joostlek]

Proposed Changes

(Describe the changes and rationale behind them)

A regression in #1162, released in v1.4.0. Reading the display on a SKY raises:

mashumaro.exceptions.MissingField: Field "when_dark" of type
DisplayScreensaverWhenDark is missing in DisplayScreensaverModes instance

That propagates out of device() and display(), so a SKY cannot be set up at all on v1.4.0.

The cause is that I modelled screensaver.modes from a TIME, which reports time_based and when_dark, and made both fields required. A SKY reports time_based and screen_off:

"screensaver": {
    "enabled": true,
    "modes": {
        "screen_off": { "enabled": false },
        "time_based": { "enabled": false }
    },
    "widget": ""
}

Which modes a device reports depends on the hardware, so every mode is now optional rather than the model asserting any particular set. screen_off is modelled, and added to ScreensaverMode so it can be selected on a SKY.

Why it was missed

Every device fixture in the repo is a TIME — device.json and device2.json are an LM 37X8, device3.json is an sa8 — so there was no SKY payload to contradict the assumption. This adds device_sky.json, taken from a real SKY, to the parametrized test_get_device, plus a test covering the mode difference explicitly. The snapshot changes are purely additive: the existing TIME snapshots gain 'screen_off': None, with no values altered.

Compatibility

time_based and when_dark are now | None and so need a None check. This is visible to type checkers, and updating this repo's own tests surfaced 12 such errors, which is a fair preview of what a consumer will see.

It is not a behavioural break, though: previously a missing mode raised MissingField rather than yielding None, so any code path that worked before still works. Only code that already had to handle the exception now gets a None instead.

Verified both ways: a live LaMetric TIME (sa8, OS 3.2.7) still reads correctly with when_dark populated and screen_off as None, and the SKY payload now parses with the reverse.

Related Issues

(Github link to related issues or pull requests)

Regression from #1162.

🤖 Generated with Claude Code