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Preserve row type when .annotate() is called on a generic QuerySet #3379

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sobolevn merged 1 commit into from
May 12, 2026
+41 −20
Merged

Preserve row type when .annotate() is called on a generic QuerySet #3379

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48 changes: 28 additions & 20 deletions mypy_django_plugin/transformers/querysets.py
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Original file line number Diff line number Diff line change
Expand Up @@ -408,6 +408,31 @@ def _extract_model_type_var_upper_bound(ctx: MethodContext) -> Instance | None:
return None


def _resolve_annotate_row_type(
api: TypeChecker,
default_return_type: Instance,
annotated_model: ProperType,
expression_types: dict[str, MypyType],
) -> MypyType:
if len(default_return_type.args) <= 1:
return annotated_model
original_row_type = get_proper_type(default_return_type.args[1])
if isinstance(original_row_type, TypedDictType):
return api.named_generic_type(
"builtins.dict",
[api.named_generic_type("builtins.str", []), AnyType(TypeOfAny.from_omitted_generics)],
)
if isinstance(original_row_type, TupleType):
if original_row_type.partial_fallback.type.has_base("typing.NamedTuple"):
# Rebuild the NamedTuple with existing fields + annotation fields.
annotation_fields = {name: AnyType(TypeOfAny.from_omitted_generics) for name in expression_types}
return helpers.extend_oneoff_named_tuple(api, "Row", original_row_type, annotation_fields)
return api.named_generic_type("builtins.tuple", [AnyType(TypeOfAny.from_omitted_generics)])
if isinstance(original_row_type, Instance) and helpers.is_model_type(original_row_type.type):
return annotated_model
return original_row_type


def extract_proper_type_queryset_annotate(ctx: MethodContext, django_context: DjangoContext) -> MypyType:
django_model = helpers.get_model_info_from_qs_ctx(ctx, django_context)
if django_model is None:
Expand All @@ -424,7 +449,8 @@ def extract_proper_type_queryset_annotate(ctx: MethodContext, django_context: Dj
if expression_types:
fields_dict = helpers.make_typeddict(api, expression_types)
upper_annotated = get_annotated_type(api, upper_bound, fields_dict=fields_dict)
return default_return_type.copy_modified(args=[upper_annotated, upper_annotated])
row_type = _resolve_annotate_row_type(api, default_return_type, upper_annotated, expression_types)
return default_return_type.copy_modified(args=[upper_annotated, row_type])
return AnyType(TypeOfAny.from_omitted_generics)

default_return_type = get_proper_type(ctx.default_return_type)
Expand Down Expand Up @@ -452,25 +478,7 @@ def extract_proper_type_queryset_annotate(ctx: MethodContext, django_context: Dj
fields_dict = helpers.make_typeddict(api, all_fields)
annotated_type = get_annotated_type(api, django_model.typ, fields_dict=fields_dict)

row_type: MypyType
if len(default_return_type.args) > 1:
original_row_type = get_proper_type(default_return_type.args[1])
row_type = original_row_type
if isinstance(original_row_type, TypedDictType):
row_type = api.named_generic_type(
"builtins.dict", [api.named_generic_type("builtins.str", []), AnyType(TypeOfAny.from_omitted_generics)]
)
elif isinstance(original_row_type, TupleType):
if original_row_type.partial_fallback.type.has_base("typing.NamedTuple"):
# Rebuild the NamedTuple with existing fields + annotation fields.
annotation_fields = {name: AnyType(TypeOfAny.from_omitted_generics) for name in expression_types}
row_type = helpers.extend_oneoff_named_tuple(api, "Row", original_row_type, annotation_fields)
else:
row_type = api.named_generic_type("builtins.tuple", [AnyType(TypeOfAny.from_omitted_generics)])
elif isinstance(original_row_type, Instance) and helpers.is_model_type(original_row_type.type):
row_type = annotated_type
else:
row_type = annotated_type
row_type = _resolve_annotate_row_type(api, default_return_type, annotated_type, expression_types)
return default_return_type.copy_modified(args=[annotated_type, row_type])


Expand Down
13 changes: 13 additions & 0 deletions tests/typecheck/managers/querysets/test_annotate.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -1012,3 +1012,16 @@

class FooModel(models.Model):
objects = FooManager()

- case: values_then_annotate_on_generic_queryset_typevar
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@delfick delfick May 13, 2026 •
edited
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Seems here is another case that shows a problem

- case: values_are_carried_through
  main: |
    from typing import Any
    from typing_extensions import reveal_type, TypeVar
    from django.db import models
    import myapp.models

    with_annotate = myapp.models.Thing.objects.all().annotate(foo=models.Max("id"))

    reveal_type(with_annotate) # N: Revealed type is "django.db.models.query.QuerySet[myapp.models.Thing@AnnotatedWith[TypedDict({'foo': Any})], myapp.models.Thing@AnnotatedWith[TypedDict({'foo': Any})]]"

    with_values = with_annotate.values("id").distinct()

    reveal_type(with_values) # N: Revealed type is "django.db.models.query.QuerySet[myapp.models.Thing@AnnotatedWith[TypedDict({'foo': Any})], TypedDict({'id': int})]"
  installed_apps:
    - myapp
  files:
    - path: myapp/__init__.py
    - path: myapp/models.py
      content: |
        from django.db import models
        from typing import Self

        class Thing(models.Model):
            pass

If I change with_values = with_annotate.values("id").distinct() to not have the distinct() then it passes.

edit: and seems similar for doing a slice qs[:max_sample_results]

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@delfick delfick May 13, 2026

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also I've noticed that the .annotate will erase the custom queryset type if there is one.

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@delfick delfick May 13, 2026

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I've run out of time to investigate, but seems for that new test case above, the fix will be something to do with

django-stubs/mypy_django_plugin/transformers/querysets.py

Line 508 in 18413d5

return default_return_type.copy_modified(args=[annotated_type, annotated_type])

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@federicobond federicobond May 13, 2026

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Yes, both cases should be fixed by #3383

main: |
from typing import Any
from typing_extensions import reveal_type, TypeVar
from django.db import models

_Model = TypeVar("_Model", bound=models.Model)

def latest_max(qs: models.QuerySet[_Model]) -> dict[str, Any] | None:
annotated = qs.values("id").annotate(foo=models.Max("id"))
reveal_type(annotated) # N: Revealed type is "django.db.models.query.QuerySet[django.db.models.base.Model, dict[str, Any]]"
return annotated.first()
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