Fix homeassistant.start trigger

[azogue]

Description:

Fix the async_block_till_done coroutine in order to fix the homeassistant.start trigger.

In my experience, when passing through components/automation/homeassistant.py:async_trigger(), core.py:async_start() is finished, so state is CoreState.running and condition is never met (as commented in #8185)

The while loop has no meaning there with the call to list.clear() in its body, and It looks like a last yield from asyncio.sleep(0) is needed to trigger the automations as expected.

Second attempt, I think a little more elegant than #8216 (I couldn't integrate changes in the same branch, so I'm making a new PR here), which I'm closing now.

Related issue (if applicable): fixes #8185 / #7058

Example entry for configuration.yaml (if applicable):

automation:
- alias: TEST HA start
  trigger:
    platform: homeassistant
    event: start
  action:
    - service: persistent_notification.create
      data:
        title: 'HA init'
        message: "Home Assistant start: {{ as_timestamp(now())| timestamp_local}}."
        notification_id: "init_notif"

Checklist:

If the code does not interact with devices:

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass

[mention-bot]

@azogue, thanks for your PR! By analyzing the history of the files in this pull request, we identified @balloob, @pvizeli and @fabaff to be potential reviewers.

[lwis]

I'd like to see a test for this, to prove the functionality and to protect against future breakage.

Also, this looks like it broke a bunch of tests.

[balloob]

The reason we yield inside the while loop is so that we give scheduled callbacks (which are called with loop.call_soon) time to execute as they are not added to self._pending_tasks.

[azogue]

thanks for the explanation!

[pvizeli]

Thanks for analyse. I think a better fix is to add here: https://github.com/home-assistant/home-assistant/blob/dev/homeassistant/core.py#L171 a sleep 0 with a comment.

[azogue]

Hi @pvizeli, there the sleep(0) won't work (tried). But just before self.state = CoreState.running is working ok. That was the first attempt of a fix, in #8216, but looked somehow non natural, so I started to messing around async_block_till_done (making a last and unconditional sleep(0) there also works)

Any idea on the explanatory comment?

[pvizeli]

Looks good. I was never able to reproduce it

[azogue]

@pvizeli, In my test/dev machine, with a simple yaml config with a telegram_bot, some cameras, a media_player, some scripts and automations, without this fix homeassistant.start never triggers, but with it always works as expected. The only 'non standard' configuration I can think of about this test machine is that automations are defined in configuration.yaml and in other yaml files (config with packages), but this couldn't make any difference, isn't it?

I tried to change tests/components/automation/test_homeassistant.py to reproduce this behaviour, but I failed. The test always passes, with or without this fix.

Thanks for reviewing, btw!

[pvizeli]

That is not possible to have test for that. It need a perfect timing to run into this problem.

[lwis]

Can confirm this also fixes it for me, nice work @azogue