Inheritance from models fields

[AlwxSin]

I've got the following snippet

from django.db import models

class PhoneField(models.CharField):
    """Phone field based on CharField with validation."""

    def __init__(self, *args, **kwargs) -> None:
        """Init."""
        options = {
            "max_length": 30,
            "validators": (must_be_valid_number, ),
        }
        options.update(kwargs)
        super().__init__(*args, **options)

And there are two problems:

• First - models.py:3 error: Missing type parameters for generic type "CharField"

• And second

models.py:13: error: Argument 2 to "__init__" of "CharField" has incompatible type "**Dict[str, object]"; expected "Union[str, bytes, None]"
models.py:13: error: Argument 2 to "__init__" of "CharField" has incompatible type "**Dict[str, object]"; expected "Optional[str]"
models.py:13: error: Argument 2 to "__init__" of "CharField" has incompatible type "**Dict[str, object]"; expected "bool"
models.py:13: error: Argument 2 to "__init__" of "CharField" has incompatible type "**Dict[str, object]"; expected "Optional[int]"
models.py:13: error: Argument 2 to "__init__" of "CharField" has incompatible type "**Dict[str, object]"; expected "Optional[Iterable[Union[Tuple[Any, Any], Tuple[str, Iterable[Tuple[Any, Any]]]]]]"
models.py:13: error: Argument 2 to "__init__" of "CharField" has incompatible type "**Dict[str, object]"; expected "str"
models.py:13: error: Argument 2 to "__init__" of "CharField" has incompatible type "**Dict[str, object]"; expected "Iterable[Callable[..., None]]"
models.py:13: error: Argument 2 to "__init__" of "CharField" has incompatible type "**Dict[str, object]"; expected "Optional[Dict[str, Any]]"

How can I annotate generic CharField?

And how can I pass kwargs to super?

[youssefm]

Can you try completing the annotation on your init definition?

def __init__(self, *args: Any, **kwargs: Any) -> None:

and type your options variable:

options: Dict[str, Any] = {

[AlwxSin]

I did and incompatible type "**Dict[str, object]" errors are gone.

But I still get models.py:3 error: Missing type parameters for generic type "CharField" error.

[layoaster]

I also have the same error: Missing type parameters for generic type "DateTimeField" when subclassing a Django DateTime field.

class AutoDateTimeField(models.DateTimeField):
    """
    A custom model field based on :class:`django.db.models.DateTimeField` that
    updates itself to `django.utils.timezone.now()` upon updating it's model.
    """

    def pre_save(self, model_instance, add) -> datetime:
        """
        Hook to timestamp model before it's saved.
        """
        return timezone.now()

Any workaround?

[sobolevn]

All fields are generic with kind of 2: https://github.com/typeddjango/django-stubs/blob/master/django-stubs/db/models/fields/init.pyi#L45

You can try to do something like this:

from typing import TypeVar

# __set__ value type
_ST = TypeVar("_ST")
# __get__ return type
_GT = TypeVar("_GT")

class AutoDateTimeField(models.DateTimeField[_ST, _GT]):
    ...

[layoaster]

@sobolevn doesn't work, it results in:

    class AutoDateTimeField(models.DateTimeField[_ST, _GT]):
TypeError: 'type' object is not subscriptable

[sobolevn]

That because of https://github.com/django/django/pull/12405

Sadly, I don't have any ideas on how to fix it except # type: ignore

[blueyed]

That because of django/django#12405

Sadly, I don't have any ideas on how to fix it except # type: ignore

Just for reference: this can be fixed now with django_stubs_ext:

import django_stubs_ext

django_stubs_ext.monkeypatch()

[psasselum]

I encountered this error because I was typing something that was already implicitly typed correctly:

-     name: models.CharField = models.CharField(max_length=100, primary_key=True)
+     name = models.CharField(max_length=100, primary_key=True)