Update device registry of MQTT Switch

[emontnemery]

Description:

Support update of device registry so Hass doesn't need to be restarted to, for example, show updated firmware version of the device.

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.

If the code does not interact with devices:

• Tests have been added to verify that the new code works.

[OttoWinter]

This line can be removed after this

[emontnemery]

Why is it ok to remove the device_info function?

[OttoWinter]

Not all of it. But everything except for identifiers/connections can be removed as now that's handled above.

[emontnemery]

OK, I think it's fixed now.

[OttoWinter]

The lines are still there 🌚
https://github.com/home-assistant/home-assistant/pull/19540/files#diff-745593be832eda57f1414e7948e5c158R1037

[emontnemery]

Yes, but the code is now no longer duplicated in MqttEntityDeviceInfo.device_info_discovery_update(), so shouldn't be removed from MqttEntityDeviceInfo.device_info().

[OttoWinter]

Check if self._config_entry is None before. If the user tries to configure the device registry through YAML, this line will raise an AttributeError

[emontnemery]

I thought device registry only works through discovery as documented: https://www.home-assistant.io/components/switch.mqtt/#device
Can you give an example of when this errors so I can test and verify your suggestion?

[OttoWinter]

Example is in previous comment.

Previously, this would not do anything in the case of yaml config. But now this will raise an attributeerror. We can do better than that. Let's print a proper warning/error

[emontnemery]

But function device_info_discovery_update is only called if mqtt discovery message is received again after the switch had been discovered, how can this happen for a device configured trough yaml? An example of exactly what yaml triggers an error would be helpful.

[emontnemery]

I think this is fixed/clearer now that the duplicated code has been removed.

[emontnemery]

@OttoWinter Do you think this is OK to merge now after the duplicated code was removed?

[thomasloven]

I can't see anything indicating it, but I'm not really comfortable with the entity registry, so just to make sure:
This does not remove the ability to add mqtt devices via legacy yaml config, right?

[emontnemery]

@thomasloven That's absolutely not the intention. The purpose of this PR is to allow the device registry to be updated without a restart of Hass. A typical use case would firmware version to be correctly shown in Hass UI.

[thomasloven]

Thank you for the clarification.