Using TextChoices with Blank Fields in Django

When using Django's models.TextChoices with a field that has blank=True, you're encountering an issue because enumeration types in Django have specific requirements for handling empty values.

The Issue

The problem with your approach is that enumeration types like TextChoices require all values to match the concrete data type. Since TextChoices expects string values, using None as a value will cause an error.

Correct Solution

Instead of adding a None value member to your enumeration, you should use the __empty__ attribute on the class:

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from django.db import models
from django.utils.translation import gettext_lazy as _

class SomeType(models.TextChoices):
    FIRST_TYPE = 'first_type', 'first type'
    SECOND_TYPE = 'second_type', 'second type'
    
    # This defines the blank label
    __empty__ = '---------'

Then in your model:

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class YourModel(models.Model):
    type = models.CharField(
        max_length=20,
        choices=SomeType.choices,
        blank=True
    )

Additional Information

1. Django will automatically handle the blank option in forms when blank=True is set on the field.

2. The __empty__ attribute is specifically designed for enumeration types to override the default blank label.

3. For non-enumeration choices (like regular tuples), you would add a tuple with None or an empty string, but for enumeration types, this approach doesn't work because of type constraints.

4. Remember that a new migration is created each time the order of choices changes, so try to keep your choices relatively static.