MQTT light using "template" schema generates warnings when status payloads arrive with only { "state": "off" }

[sumnerboy12]

The problem

I have some DIY LED strip controller firmware which is publishing MQTT self-discovery payloads to configure light entities in Home Assistant, using the template schema.

When the LED strip is turned on the firmware will publish a status payload which looks like {"state": "on", "brightness": 123, "color_temp": 345}. However when the strip is turned off, the status payload published is simply {"state": "off"}.

Looking in https://github.com/home-assistant/core/blob/dev/homeassistant/components/mqtt/light/schema_template.py it looks like there is no handling for the case where a status update is received, but non-mandatory values are missing in the payload.

I think when the light is turned off it should accept a payload with no brightness or color_temp, without generating warnings in the log, given they are redundant for this state.

What version of Home Assistant Core has the issue?

core-2025.3.4

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

MQTT

Link to integration documentation on our website

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

Diagnostics information

No response

Example YAML snippet

Anything in the logs that might be useful for us?

Logger: homeassistant.components.mqtt.light.schema_template
Source: components/mqtt/light/schema_template.py:245
integration: MQTT (documentation, issues)
First occurred: March 22, 2025 at 10:55:38 PM (52 occurrences)
Last logged: 8:51:58 AM

Invalid color temperature value received

Additional information

No response

[home-assistant]

Hey there @emontnemery, @jbouwh, @bdraco, mind taking a look at this issue as it has been labeled with an integration (mqtt) you are listed as a code owner for? Thanks!

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[jbouwh]

I saw your linked PR. For this case you might want to consider using the json schema. But I agree on the warnings that they should be improved.

[sumnerboy12]

I saw your linked PR. For this case you might want to consider using the json schema. But I agree on the warnings that they should be improved.

Yep - I did try the json schema, but my firmware has some additional complexity in the state payloads, whereby a single device can control multiple LED strips and they share the same MQTT topics. Hence the state payload includes a { "strip": 1 } property to indicate which light is being updated.

As a result the value templates I use look like;

state_template: '{% if value_json.strip == 1 %}{{ value_json.state }}{% endif %}'

And therefore the json schema is not suitable.

Thanks for your comments on my PR, I will add the tests as get that updated ASAP.

[sumnerboy12]

Fixed via #141177