Presence of transition parameter influences brightness in ON command

[Otah]

Bug Report

What happened

When a light is on and has e.g. brightness: 50, sending a command {"state": "ON", "transition": 1} sets the brightness to maximum (255). Whereas if you send just {"state": "ON"}, nothing happens (= the light stays on with brightness at level 50).

It behaves the same way no matter what the actual value of transition is. Just its presence changes the behavior. The same situation is also if the default transition is set in the device-specific options.

What did you expect to happen

I expect if sending an ON command to a light which is already on, nothing will happen. I definitely not expect that it should change the brightness and especially I don't expect that presence of transition parameter should change how it behaves.

How to reproduce it (minimal and precise)

Given a Philips White Ambiance bulb (I only have Philips Hue bulbs, no other manufacturer to test) without default transition parameter in device-specific options, publishing one by one to its /set topic:

{"state": "ON", "brightness": 50} // turns on the light and sets the brightness to 50
{"state": "ON"}                   // correctly does nothing, as the light is already on
{"state": "ON", "transition": 1}  // incorrectly increases the brightness to max

Debug Info

zigbee2mqtt version: commit 26ad2a (version 1.6.0), was also present on 927c4db
CC253X firmware version: I think this is a software issue, but I can provide if necessary

From the log, I'd guess it's connected to the fact that the transition parameter changes the Zigbee command from:
Zigbee publish to device 'ambianceBulb3', genOnOff - on - {} - {"manufSpec":0,"disDefaultRsp":0} - 11
to:
Zigbee publish to device 'ambianceBulb3', genLevelCtrl - moveToLevelWithOnOff - {"level":255,"transtime":10} - {"manufSpec":0,"disDefaultRsp":0} - 11

The topic sounds similar to the #1260 but not the issue itself.

[Koenkk]

Should be fixed in latest zigbee2mqtt dev.

[pepp86]

Experiencing the same issue when switching lamps off with transition, brightness is set to 0 which makes some trouble in my installation.

[Koenkk]

@pepp86 I guess it depends on the bulb, why dont you leave out the transition?

[pepp86]

@Koenkk Having this issue on all devices supporting transition.

I want to use transition, so I can't leave it out!?

[Koenkk]

@copystring @pepp86 your issue should be fixed in latest dev, please check and confirm.

[copystring]

Seems to work. It remembers the brightness.

[Koenkk]

Thanks, assuming this can be closed now.