Allow specifying template entities based on triggers

[balloob]

Breaking change

Proposed change

Foundation for a trigger entity.

Allows you to specify any number of triggers as sources. Trigger data is forwarded to the entities to render their value off.

Use cases: webhook entities, MQTT entities etc, listen more efficiently to state changes etc

Placed under template: instead of sensor, the configuration of this integration mimics the exact same configuration (minus platform: template, plus trigger:) as is used for platforms.

template:
- trigger:
    platform: event
    event_type: test_event
  sensors:
    hello:
      friendly_name: Hello
      value_template: "{{ trigger.event.data.beer }}"

- trigger:
    platform: webhook
    webhook_id: my-super-secret-webhook-id
  sensors:
    temperature:
      friendly_name: "Webhook Temperature"
      value_template: "{{ trigger.json.temperature }}"

Screenshot.2021-03-21.at.20.59.29.mp4

Ideas for follow-up work that I won't include in this PR:

• support for trigger-based binary sensors
• Allow defining state-based template entities at top level (so no trigger)
• support trigger entities in reload service
• support trigger_variables and variables (processed post-trigger)

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example entry for configuration.yaml:

# Example configuration.yaml

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request: Document trigger entity home-assistant.io#17092

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist
• The code has been formatted using Black (black --fast homeassistant tests)
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

If the code communicates with devices, web services, or third-party tools:

• The manifest file has all fields filled out correctly.
  Updated and included derived files by running: python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt.
  Updated by running python3 -m script.gen_requirements_all.
• Untested files have been added to .coveragerc.

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To help with the load of incoming pull requests:

• I have reviewed two other open pull requests in this repository.

[pvizeli]

did we not fade out *_template ?

[amelchio]

I think this would fit better as a trigger: section of existing template entities. That would save you from having to grow things like icon_template. I think it would also make it easier to learn the feature and it could decrease the amount of documentation needed.

That is, something like this:

template:
  - trigger:
      platform: event
      event_type: test_event
    sensor:
      - name: Hello
        value_template: "{{ trigger.event.data.beer }}"

  - trigger:
      platform: webhook
      webhook_id: my-super-secret-webhook-id
    sensor:
      name: "Webhook Temperature"
      value_template: "{{ trigger.json.temperature }}"

Edit: the above goes with the new config layout, it can of course also be added to the existing for a smaller change:

sensor:
  - platform: template
    trigger:
      platform: event
      event_type: test_event
    sensors:
      beer:
        name: Hello
        value_template: "{{ trigger.event.data.beer }}"
  - platform: template
    trigger:
      platform: webhook
      webhook_id: my-super-secret-webhook-id
    sensors:
      temperature:
        name: "Webhook Temperature"
        value_template: "{{ trigger.json.temperature }}"

On a meta note, this is another example where an architectural discussion is missing. Now we already have an implementation that people are attached to and discussion is very hard.

[balloob]

@amelchio the problem is that template entities have their own way of deciding when to update: when any depend state has changed. So would we disable that then when a trigger is defined? Seems like a confusing user experience

[balloob]

Updated the PR and made it now a new top-level template integration configuration option.

[balloob]

I think a remaining open question is how much we should align top-level configuration with the platform configuration.

Current platform configuration

# Example configuration.yaml entry
sensor:
  - platform: template
    sensors:
      solar_angle:
        friendly_name: "Sun angle"
        unit_of_measurement: "degrees"
        value_template: "{{ state_attr('sun.sun', 'elevation') }}"

      sunrise:
        value_template: "{{ state_attr('sun.sun', 'next_rising') }}"

Proposed integration configuration

template:
- trigger:
    platform: event
    event_type: test_event
  sensor:
    - friendly_name: Hello
      value_template: "{{ trigger.event.data.beer }}"

- trigger:
    platform: webhook
    webhook_id: my-super-secret-webhook-id
  sensor:
    friendly_name: "Webhook Temperature"
    value_template: "{{ trigger.json.temperature }}"

Differences

All keys to define a sensor in both cases are exactly the same. The differences are:

1. Platform uses plural version sensors, integration config uses platform domain/singular sensor
2. Platform requires to define a slug for each entity and uses this for entity ID (but does not use this as unique id 🤔)

[balloob]

Alright, went ahead and aligned the integration top-level with the existing platform integration.

I am unable to add trigger support to existing platform configuration because triggers require an async validator config.py (because of device triggers). This is not supported for platforms.