Config Flow Validation Error with Optional EntitySelector

Development
1

Hi everyone,

I’m encountering a validation issue in the config flow for a custom integration when using an optional EntitySelector for a temperature sensor. When the user leaves this optional field empty and submits the form, a validation error occurs, preventing the configuration from proceeding.

Here’s the relevant part of my voluptuous schema definition within the ConfigFlow’s async_step_user:

# (Inside async_step_user or a helper function like get_user_schema)
import voluptuous as vol
from homeassistant.helpers import selector
from homeassistant.components.sensor import SensorDeviceClass
from .const import CONF_TEMP_SENSOR # CONF_TEMP_SENSOR = "temp_sensor"

# ... other fields ...

vol.Optional(
    CONF_TEMP_SENSOR, default=user_input.get(CONF_TEMP_SENSOR) # Trying to preserve input on redisplay
): selector.EntitySelector(
    selector.EntitySelectorConfig(
        domain="sensor", device_class=SensorDeviceClass.TEMPERATURE
    )
),

# ... other fields ...

I also have logic after successful validation to remove the CONF_TEMP_SENSOR key from the data if it’s None or an empty string before creating the config entry:

# (Inside async_step_user, after validation passes)
temp_sensor_value = user_input.get(CONF_TEMP_SENSOR)
if not temp_sensor_value: # Checks for None or empty string
    user_input.pop(CONF_TEMP_SENSOR, None) # Remove key if it exists

return self.async_create_entry(title=info["title"], data=user_input)

Problem: The validation fails before my cleanup logic runs. My hypothesis is that when the optional EntitySelector is left empty, the frontend might submit it as CONF_TEMP_SENSOR: "". The vol.Optional allows the key, but the EntitySelector validator then rejects the empty string "" as an invalid entity ID. The default=user_input.get(...) might complicate this further, especially on form redisplay after other errors.

Question:

  1. Is my hypothesis likely correct? Is the standard behavior for an empty optional EntitySelector to submit ""?
    1. What is the recommended way to define an optional EntitySelector in a config flow schema to avoid this validation error when the user intentionally leaves it blank? Should I simply remove the default=... part like this?
  3. ```python

  4. vol.Optional(CONF_TEMP_SENSOR): selector.EntitySelector(...)

  5. ```
    1. Is there a different default value (like None) or schema structure I should be using?
      Any insights or pointers to best practices would be greatly appreciated! Thanks!