Raising exceptions with translations

Logging exceptions with translation support

Translation support applies to HomeAssistantError and subclasses like ServiceValidationError. When a translation_domain and translation_key is set and the error message is added in strings.json, it is no longer needed to add the error message string for the local logging. Home Assistant will automatically fetch the English error message from the translation cache.

When raising HomeAssistantError or a subclass with translation support we should remove the log message from the argument list to enable it to be fetched from the translation cache.

For example:

async def async_select_index(hass: HomeAssistant, index: int) -> None:
    """Setup the config entry for my device."""
    try:
        check_index(index)
    except ValueError as exc:
        raise ServiceValidationError(
            translation_domain=DOMAIN,
            translation_key="invalid_index",
            translation_placeholders={
                "index": index,
                "expected": expected,
            },
        ) from exc

The error message is placed in strings.json:

{
    ...
    "exceptions": {
        "invalid_index": {
            "message": "An invalid index is selected, expected: {expected}, got: {index}"
        }
    }
}