ModernForms fan: light flashes old brightness value when coming on

[eliwind]

The problem

The ModernForms fan light internally has a notion of "brightness" that it retains whether on or off; if you toggle it on, it comes on to the brightness setting from the last time it was on. This is good.

However, if you turn it on while specifying a brightness (e.g. using the light.turn_on service and providing a brightness value; or sliding the brightness slider to a non-zero value while the light is off in the lovelace UI), then the light should come on at the newly selected brightness value. But in fact, it firstomes on initially at its old brightness and then quickly changes to the newly-selected brightness, appearing to flash.

It seems that the way to make this work as expected is rather than sending a single request to the light changing both brightness and "on" state in one shot, to first set the brightness to the new value, and only after that has adjusted, to send a separate request to turn the light on.

What version of Home Assistant Core has the issue?

core-2021.11.3

What was the last working version of Home Assistant Core?

No response

What type of installation are you running?

Home Assistant Container

Integration causing the issue

Modern Forms

Link to integration documentation on our website

https://www.home-assistant.io/integrations/modern_forms/

Example YAML snippet

No response

Anything in the logs that might be useful for us?

No response

Additional information

This line of code seems to be the source of the problem:

core/homeassistant/components/modern_forms/light.py

Line 129 in 6749930

await self.coordinator.modern_forms.light(**data)

While it seems like a reasonable request of the fan to both turn on and set brightness in one shot, empirically the result is that the light turns on at its previous brightness level first and then adjusts the brightness after. Doing two separate requests seems to make it work here.

[probot-home-assistant]

modern_forms documentation
modern_forms source
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[probot-home-assistant]

Hey there @wonderslug, mind taking a look at this issue as it has been labeled with an integration (modern_forms) you are listed as a code owner for? Thanks!
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[wonderslug]

Howdy, Yeah seeing this. It probably should be adjusted at the library level, not as much at the HA level. Ive setup an issue wonderslug/aiomodernforms#99 and will see if I can make the adjustments soon.