Problem with creating migrations for subclassed field changes.

[Wolfgang Fehr]

makemigrations gives out 'No changes detected' for changes on a sub-subclass of CharField (only tested with this field).

When creating a field as seen below (DummyCharField), a new migration only gets created if kwargs['max_length'] = 255 is wrapped inside an if.

class BaseDummyCharField(models.CharField):
    def __init__(self, *args, **kwargs):
        if 'max_length' not in kwargs:
            kwargs['max_length'] = 64
        super().__init__(*args, **kwargs)


class DummyCharField(BaseDummyCharField):
    def __init__(self, *args, **kwargs):
        # Without the if 'makemigrations' does not recognize changes.
        # Previous max_length (in initial migration) is 64.
        if 'max_length' not in kwargs:
            kwargs['max_length'] = 255
        super().__init__(*args, **kwargs)


class DummyModel(models.Model):
    dummy = DummyCharField()

(Also reproducable in version 2.0.6, maybe others as well.)

[Mariusz Felisiak]

You're use case is described in ​Writing custom model fields documentation. It seems that ​deconstruct() is missing which is very important for migrations.

Closing per TicketClosingReasons/UseSupportChannels.

[Wolfgang Fehr]

I tried out deconstruct(), but still had the same problem. (also see ​Stackoverflow)
(also tried deconstruct() in the parent-field)

[Carlton Gibson]

This is still not a support channel. See TicketClosingReasons/UseSupportChannels.