homeassistant-integration

name	homeassistant-integration
description	Home Assistant custom integration development patterns, best practices, and conventions. Use when creating or modifying entities, config flows, coordinators, or any Home Assistant integration code.

Home Assistant Custom Integration Development

This skill provides knowledge for developing Home Assistant custom integrations following best practices.

Project Structure

custom_components/homevolt_local/
├── __init__.py          # Entry point with async_setup_entry
├── manifest.json        # Integration metadata and dependencies
├── const.py             # Domain and constants
├── config_flow.py       # UI configuration flow
├── coordinator.py       # Data update coordinator
├── models.py            # Data models
├── sensor.py            # Sensor platform
├── strings.json         # User-facing text and translations
├── services.yaml        # Service definitions (if applicable)
└── translations/        # Language translations

tests/                   # Integration tests (at repo root)
├── conftest.py          # Shared pytest fixtures
└── test_*.py            # Test files

Core Patterns

Entity Development

class MySensor(CoordinatorEntity, SensorEntity):
    """Sensor entity using coordinator pattern."""

    _attr_has_entity_name = True  # Required for proper naming

    def __init__(self, coordinator: MyCoordinator) -> None:
        """Initialize the sensor."""
        super().__init__(coordinator)
        self._attr_unique_id = f"{coordinator.config_entry.entry_id}_sensor_name"
        self._attr_translation_key = "sensor_name"  # Use translations
        self._attr_device_info = DeviceInfo(
            identifiers={(DOMAIN, coordinator.config_entry.entry_id)},
            name="Device Name",
            manufacturer="Manufacturer",
            model="Model",
        )

    @property
    def native_value(self) -> StateType:
        """Return the state of the sensor."""
        return self.coordinator.data.some_value

Coordinator Pattern

class MyCoordinator(DataUpdateCoordinator[MyData]):
    """Data update coordinator."""

    def __init__(self, hass: HomeAssistant, config_entry: ConfigEntry) -> None:
        """Initialize coordinator."""
        super().__init__(
            hass,
            _LOGGER,
            name=DOMAIN,
            update_interval=timedelta(seconds=30),
        )
        self.config_entry = config_entry

    async def _async_update_data(self) -> MyData:
        """Fetch data from API."""
        try:
            return await self._fetch_data()
        except ApiConnectionError as err:
            raise UpdateFailed(f"Connection error: {err}") from err
        except ApiAuthError as err:
            raise ConfigEntryAuthFailed(f"Auth error: {err}") from err

Config Flow

class MyConfigFlow(ConfigFlow, domain=DOMAIN):
    """Handle a config flow."""

    VERSION = 1

    async def async_step_user(
        self, user_input: dict[str, Any] | None = None
    ) -> ConfigFlowResult:
        """Handle the initial step."""
        errors: dict[str, str] = {}

        if user_input is not None:
            try:
                info = await validate_input(self.hass, user_input)
            except CannotConnect:
                errors["base"] = "cannot_connect"
            except InvalidAuth:
                errors["base"] = "invalid_auth"
            else:
                await self.async_set_unique_id(info["unique_id"])
                self._abort_if_unique_id_configured()
                return self.async_create_entry(title=info["title"], data=user_input)

        return self.async_show_form(
            step_id="user",
            data_schema=SCHEMA,
            errors=errors,
        )

Sensor Classifications

Power Sensors

_attr_device_class = SensorDeviceClass.POWER
_attr_native_unit_of_measurement = UnitOfPower.WATT
_attr_state_class = SensorStateClass.MEASUREMENT
_attr_suggested_display_precision = 0

Energy Sensors (Total Increasing)

_attr_device_class = SensorDeviceClass.ENERGY
_attr_native_unit_of_measurement = UnitOfEnergy.KILO_WATT_HOUR
_attr_state_class = SensorStateClass.TOTAL_INCREASING
_attr_suggested_display_precision = 2

Battery Percentage

_attr_device_class = SensorDeviceClass.BATTERY
_attr_native_unit_of_measurement = PERCENTAGE
_attr_state_class = SensorStateClass.MEASUREMENT

Common Anti-Patterns to Avoid

# ❌ Blocking operations in event loop
data = requests.get(url)  # Blocks event loop

# ❌ Missing error handling
data = await self.api.get_data()  # No exception handling

# ❌ Hardcoded strings
self._attr_name = "Temperature"  # Not translatable

# ❌ Missing unique_id
# Entity without unique_id cannot be managed in UI

Correct Patterns

# ✅ Async operations
data = await hass.async_add_executor_job(requests.get, url)

# ✅ Proper error handling
try:
    data = await self.api.get_data()
except ApiException as err:
    raise UpdateFailed(f"API error: {err}") from err

# ✅ Translatable entity names
_attr_translation_key = "temperature"

# ✅ Always set unique_id
self._attr_unique_id = f"{entry_id}_temperature"

Testing Patterns

@pytest.fixture
def mock_config_entry() -> MockConfigEntry:
    """Return the default mocked config entry."""
    return MockConfigEntry(
        title="Test Device",
        domain=DOMAIN,
        data={CONF_HOST: "192.168.1.100"},
        unique_id="device_unique_id",
    )

async def test_sensor_value(
    hass: HomeAssistant,
    mock_config_entry: MockConfigEntry,
) -> None:
    """Test sensor returns correct value."""
    mock_config_entry.add_to_hass(hass)
    await hass.config_entries.async_setup(mock_config_entry.entry_id)
    await hass.async_block_till_done()

    state = hass.states.get("sensor.device_power")
    assert state is not None
    assert state.state == "1500"

Error Handling

Exception	When to Use
ConfigEntryNotReady	Temporary setup failure (network issue)
ConfigEntryAuthFailed	Authentication/authorization failure
UpdateFailed	Coordinator update error

Resources

• Home Assistant Developer Docs
• Integration Quality Scale
• HACS Documentation