API POST has new state validation (fix for state = 0)

[azogue]

Description:

When posting a new state of an entity through the API, if the state value is 0, the validation acts as if a state had not been sent, so it returns a 404 error code and does not update the entity state.

Problem is this validation:

new_state = data.get('state')
if not new_state:
    return self.json_message('No state specified', HTTP_BAD_REQUEST)

If new_state is a float or an integer, the 0 / 0.0 value returns the error! This has to be a null comparison (if new_state is None).

I was going crazy until I discovered the error... I have a custom sensor in an AppDaemon app which measures the difference of temperature between the interior and the exterior of the house, and it was failing mysteriously when ∆T=0.

Example entry to check the error:

curl -X POST -H "x-ha-access: [HA_PASSWD]" -H "Content-Type: application/json" -d '{"state": 0, "attributes": {"friendly_name": "Test Sensor "}}' http://[HA_IP]:8123/api/states/sensor.test_sensor

Checklist:

If the code does not interact with devices:

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass
• Tests have been added to verify that the new code works.

[mention-bot]

@azogue, thanks for your PR! By analyzing the history of the files in this pull request, we identified @balloob, @JshWright and @fabaff to be potential reviewers.

[balloob]

Cherry picked for 0.48.1