Cannot return NULL from template for color_temp or hs_color in template light

[alistairg]

The problem

HomeAssistant uses the state of hs_color and/or color_temp to correctly render full color lights, and determine which mode they're in. The 'template light' does not support returning a null value for either template, with unhandled exceptions for hs_color as it attempts to parse the return string.

Environment

• Home Assistant Core release with the issue: 0.107.7
• Last working Home Assistant Core release (if known): None
• Operating environment (Home Assistant/Supervised/Docker/venv): HASS
• Integration causing this issue: template light
• Link to integration documentation on our website:

Problem-relevant configuration.yaml

- platform: template
    lights:
      ui_alistair_s_office_overhead:
        friendly_name: Alistair's Office Overhead
        value_template: "{{ states.light.alistair_s_office_overhead.state }}"
        level_template: "{{ states.light.alistair_s_office_overhead.attributes.brightness|int if states.light.alistair_s_office_overhead.attributes.brightness else none }}"
        temperature_template: "{{ states.light.alistair_s_office_overhead.attributes.color_temp|int if states.light.alistair_s_office_overhead.attributes.color_temp else none }}"
        color_template: "{{ states.light.alistair_s_office_overhead.attributes.hs_color or none }}"

Additional information

Template should evaluate for 'None' (string constant returned by jinja's none) and pass 'None' upstream to HA.

[frenck]

This is caused by the way you access the properties.

e.g., states.light.alistair_s_office_overhead.state -> states('light.alistair_s_office_overhead')

See: https://www.home-assistant.io/docs/configuration/templating/#states

In your template you can decide if what you return (e.g., by using an if statement).

[alistairg]

No... it really isn't ;). The code expects a return value. If you look at the templates I've got, I'm checking that there is a value for the attribute and returning it cast to int or float as needed, or none. What I can't do is return 'none'.

Excerpt from 'temperature':

try:
            temperature = int(self._temperature_template.async_render())
            if self.min_mireds <= temperature <= self.max_mireds:
                self._temperature = temperature
            else:
                _LOGGER.error(
                    "Received invalid color temperature : %s. Expected: 0-%s",
                    temperature,
                    self.max_mireds,
                )
                self._temperature = None

...and (worse), color:

try:
            render = self._color_template.async_render()
            h_str, s_str = map(
                float, render.replace("(", "").replace(")", "").split(",", 1)
            )
            if (
                h_str is not None
                and s_str is not None
                and 0 <= h_str <= 360
                and 0 <= s_str <= 100
            ):
                self._color = (h_str, s_str)
            elif h_str is not None and s_str is not None:
                _LOGGER.error(
                    "Received invalid hs_color : (%s, %s). Expected: (0-360, 0-100)",
                    h_str,
                    s_str,
                )
            else:
                _LOGGER.error("Received invalid hs_color : (%s)", render)
        except TemplateError as ex:
            _LOGGER.error(ex)

Color is particularly egregious, as it'll throw an unhandled exception for anything that isn't (x,y). Lights that are not in a color mode have no state attribute (as you point out).

It should be possible to return no state attribute at runtime using the template, without an exception - and currently it isn't.

Easily fixable, bug created just so I can track it.

[frenck]

Aah right, now I get it! ✅
Will mark it.

[probot-home-assistant]

Hey there @PhracturedBlue, @tetienne, mind taking a look at this issue as its been labeled with a integration (template) you are listed as a codeowner for? Thanks!

[alistairg]

Thanks, @frenck. I'll see if I can get this fixed with a PR in the next couple of days.

[tetienne]

I agree this is a bug. And it can be indeed fixed easily.

But I'm wondering why you want to give a none value to the template.

In your exemple, you already know if your light support hs color or temperature. If it's not the case, don't add the templates would be enough.

I'm missing something?

[alistairg]

So, if you look at a colored light, when it's not in a "color" mode - it doesn't have an attributes.hs_color value. It should be possible to reflect that in the same way using templates. Some lights, when they're off, don't have a color_temp value either - even though they technically support it.

They return "None" for those values at runtime...

[alistairg]

What offends me slightly is having to check for the string value 'None' (if you return the jinja keyword none in a rendered template, you'll actually get the string "None" in Python (and not an instance of NoneType)

[tetienne]

Thx for the explanation, it make sense for me now.
That's really a use case I don't think about it when adding this feature.

[tetienne]

It will be really easy to reproduce your case with a test: https://github.com/home-assistant/core/blob/dev/tests/components/template/test_light.py#L892