Infer type for `Form.fields` to a TypedDict by randspace0 · Pull Request #3534 · typeddjango/django-stubs

randspace0 · 2026-07-28T04:18:27Z

This should solve the related issue. I have implemented what I have describe in the issue description.

Related issues

Fixes #1514

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sobolevn

Thanks! Looks interesting :)

sobolevn · 2026-07-28T10:05:56Z

+            name = forms.EmailField()  # override parent field with a different type
+
+        form = MyForm()
+        reveal_type(form.fields["age"])  # N: Revealed type is "django.forms.fields.IntegerField"


please, assert the type of form.fields instead :)

sobolevn · 2026-07-28T10:06:35Z

+        # dynamic reassignment of the whole dict is still allowed
+        form.fields = {}
+
+        # a plain, undeclared Form still falls back to the default 'dict[str, Field]' typing


Can you please add a comment to the implementation: why is that? Some reasoning would be nice to have for the history

sobolevn · 2026-07-28T10:07:00Z

+        from typing_extensions import reveal_type
+
+        class MyForm(forms.Form):
+            brands = forms.ModelChoiceField(required=True, queryset=None)  # type: ignore[var-annotated]


Why do we have a type ignore here?

UnknownPlatypus

Thanks for starting work on this. This will be a very cool and much needed feature.

I left some comments for things that could be improved.
I would also like that we check in more detail how we do similar stuff for django Model._meta.get_fields() because it feels a bit similar

UnknownPlatypus · 2026-07-28T09:52:57Z



 BASEFORM_CLASS_FULLNAME: Final = "django.forms.forms.BaseForm"
+FORM_FIELD_FULLNAME: Final = "django.forms.fields.Field"


Suggested change

FORM_FIELD_FULLNAME: Final = "django.forms.fields.Field"

FORM_FIELD_CLASS_FULLNAME: Final = "django.forms.fields.Field"

To match the other names pattern

UnknownPlatypus · 2026-07-28T14:54:28Z

+
+
+def transform_form_fields_attr_type(ctx: AttributeContext) -> MypyType:
+    """Create type `form.fields` as a TypedDict of the form's declared fields, instead of `dict[str, Field]`."""


Is a typedict a good idea ? I see a few potential issues with that (might need some test case to validate)

for f in self.fields.values(): f.widget.attrs[...] = ... will raise "object" has no attribute "widget" because TypedDict is Mapping[str, object]

del self.fields["age"] or self.fields.pop("name", None) will raise TypedDict key "age" cannot be deleted

self.fields[k] = ... -> TypedDict key must be a string literal [literal-required]

I don't know if it's possible to have a loose typedict, maybe with overloads ?

Right. I'm thinking to just extend the dict type for flexibility. So we can just type the statically analyzed field and keep the dynamic field untyped.

Something like

class MyForm(BaseForm): age = forms.IntegerField() name = forms.EmailField() class FieldsDict(dict[str, Field]): # Created on the fly @overload def __getitem__(self, key: Literal["age"]) -> IntegerField: ... @overload def __getitem__(self, key: Literal["name"]) -> EmailField: ... @overload def __getitem__(self, key: str) -> Field: ... fields: FieldsDict # Created on the fly

yes maybe, probably need to start with a few test from my previous comment to see if it works

UnknownPlatypus · 2026-07-28T14:55:22Z

+    if not isinstance(object_type, Instance):
+        return ctx.default_attr_type
+
+    field_types: dict[str, MypyType] = {}


I think we will miss the fields that are implicitly declared for exemple when using a ModelForm ?

class ArticleForm(forms.ModelForm): slug = forms.SlugField(required=False) class Meta: model = Article fields = ["name", "slug"] f.fields["name"] # E: "name" is not a valid TypedDict key; expected one of ("slug")

For ModelForm we could use django's fields_for_model(model, fields, exclude) using django_context but that might be better to redo it manually here to avoid more coupling with the django runtime ?
We would like to be less coupled at some point. See #3376

UnknownPlatypus · 2026-07-28T14:56:30Z

+    seen: set[str] = set()
+    for base_info in info.mro:
+        for stmt in base_info.defn.defs.body:
+            if isinstance(stmt, AssignmentStmt) and len(stmt.lvalues) == 1 and isinstance(stmt.lvalues[0], NameExpr):


I think this will register annotation-only attrs as fields, for ex other: forms.IntegerField but they won't be actual fields.

UnknownPlatypus · 2026-07-28T14:57:22Z

+def _iter_declared_field_names(info: TypeInfo) -> Iterator[str]:
+    """Yield each class-body-assigned attribute name once, starts from the most-derived class."""
+    seen: set[str] = set()
+    for base_info in info.mro:


We need to skip class in the mro if they don't have a form base. See https://github.com/django/django/blob/8362cdc7efc9c881fdba48ce19e89b9194de7c46/django/forms/forms.py#L38

UnknownPlatypus · 2026-07-28T14:59:46Z

+        if info.has_base(fullnames.BASEFORM_CLASS_FULLNAME) and attr_name == "fields":
+            return forms.transform_form_fields_attr_type


This might become a bit expensive since we recompute on every fields access. Maybe it's fine, people don't do that too often ?

Otherwise an option would be to do like model._meta.get_fields() by registering the result at the module scope so we can do simpel lookup to get it later. see get_or_create_annotated_type

Infer type for Form.fields to a TypedDict

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Copilot AI review requested due to automatic review settings July 28, 2026 04:18

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Merge branch 'master' into fix/infer-form-fields-type

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sobolevn reviewed Jul 28, 2026

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UnknownPlatypus reviewed Jul 28, 2026

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Type Form.fields with a synthetic dict subclass

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randspace0 requested a review from UnknownPlatypus September 2, 2026 02:09



		BASEFORM_CLASS_FULLNAME: Final = "django.forms.forms.BaseForm"
		FORM_FIELD_FULLNAME: Final = "django.forms.fields.Field"

	FORM_FIELD_FULLNAME: Final = "django.forms.fields.Field"
	FORM_FIELD_CLASS_FULLNAME: Final = "django.forms.fields.Field"



		def transform_form_fields_attr_type(ctx: AttributeContext) -> MypyType:
		"""Create type `form.fields` as a TypedDict of the form's declared fields, instead of `dict[str, Field]`."""

		if info.has_base(fullnames.BASEFORM_CLASS_FULLNAME) and attr_name == "fields":
		return forms.transform_form_fields_attr_type

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randspace0 commented Jul 28, 2026

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