developers.home-assistant/docs/creating_platform_code_review.md

title	sidebar_label
Checklist for creating a platform	Platform checklist

A checklist of things to do when you're adding a new platform.

:::info Not all existing platforms follow the requirements in this checklist. This cannot be used as a reason to not follow them! :::

0. Common

1. Follow our Style guidelines
2. Use existing constants from const.py
   • Only add new constants to const.py if they are widely used. Otherwise keep them on platform level
   • Use CONF_MONITORED_CONDITIONS instead of CONF_MONITORED_VARIABLES

1. External requirements

1. Requirements have been added to manifest.json. The REQUIREMENTS constant is deprecated.
2. Requirement version should be pinned: "requirements": ['phue==0.8.1']
3. We no longer want requirements hosted on GitHub. Please upload to PyPi.
4. Each requirement meets the library requirements.

2. Configuration

1. If the platform can be set up directly, add a voluptuous schema for configuration validation
2. Voluptuous schema extends schema from component
   (e.g., hue.light.PLATFORM_SCHEMA extends light.PLATFORM_SCHEMA)
3. Default parameters specified in voluptuous schema, not in setup_platform(...)
4. Your PLATFORM_SCHEMA should use as many generic config keys as possible from homeassistant.const
5. Never depend on users adding things to customize to configure behavior inside your platform.

import voluptuous as vol

from homeassistant.const import CONF_FILENAME, CONF_HOST
from homeassistant.components.light import PLATFORM_SCHEMA
import homeassistant.helpers.config_validation as cv

CONF_ALLOW_UNREACHABLE = "allow_unreachable"
DEFAULT_UNREACHABLE = False

PLATFORM_SCHEMA = PLATFORM_SCHEMA.extend(
    {
        vol.Required(CONF_HOST): cv.string,
        vol.Optional(CONF_ALLOW_UNREACHABLE, default=DEFAULT_UNREACHABLE): cv.boolean,
        vol.Optional(CONF_FILENAME): cv.string,
    }
)

3. Setup platform

1. Verify that the passed in configuration (user/pass/host etc.) works.
2. Group your calls to `add_entities if possible.
3. If the platform adds extra actions, the format should be <domain of your integration>.<service action name>. So if your integration's domain is "awesome_sauce" and you are making a light platform, you would register service actions under the awesome_sauce domain. Make sure that your service actions verify permissions.

4. Entity

1. Extend the entity from the integration you're building a platform for.

   from homeassistant.components.light import Light
   
   
   class HueLight(Light):
       """Hue light component."""
   

2. Avoid passing in hass as a parameter to the entity. hass will be set on the entity when the entity is added to Home Assistant. This means you can access hass as self.hass inside the entity.

3. Do not call update() in constructor, use add_entities(devices, update_before_add=True) instead.

4. Do not do any I/O inside properties. Cache values inside update() instead.

5. When dealing with time, state and/or attributes should not contain relative time since something happened. Instead, it should store UTC timestamps.

6. Leverage the entity lifecycle callbacks to attach event listeners or clean up connections.

5. Communication with devices/services

1. All API specific code has to be part of a third party library hosted on PyPi. Home Assistant should only interact with objects and not make direct calls to the API.

   # bad
   status = requests.get(url("/status"))
   # good
   from phue import Bridge
   
   bridge = Bridge(...)
   status = bridge.status()
   

   Tutorial on publishing your own PyPI package

   Other noteworthy resources for publishing python packages:
   Cookiecutter Project
   flit
   Poetry