Generic forms.ModelChoiceField (#1889)

* Add failing test

* Add generic types to ModelMultipleChoiceField

* Add generic monkey patch entry

Author: UnknownPlatypus

django-stubs/forms/models.pyi

@@ -251,20 +251,20 @@ class ModelChoiceIterator:
     def __bool__(self) -> bool: ...
     def choice(self, obj: Model) -> tuple[ModelChoiceIteratorValue, str]: ...
 
-class ModelChoiceField(ChoiceField):
+class ModelChoiceField(ChoiceField, Generic[_M]):
     disabled: bool
     help_text: _StrOrPromise
     required: bool
     show_hidden_initial: bool
     validators: list[Any]
     iterator: type[ModelChoiceIterator]
     empty_label: _StrOrPromise | None
-    queryset: QuerySet[models.Model] | None
+    queryset: QuerySet[_M] | None
     limit_choices_to: _AllLimitChoicesTo | None
     to_field_name: str | None
     def __init__(
         self,
-        queryset: None | Manager[models.Model] | QuerySet[models.Model],
+        queryset: Manager[_M] | QuerySet[_M] | None,
         *,
         empty_label: _StrOrPromise | None = ...,
         required: bool = ...,
@@ -278,27 +278,27 @@ class ModelChoiceField(ChoiceField):
         **kwargs: Any,
     ) -> None: ...
     def get_limit_choices_to(self) -> _LimitChoicesTo: ...
-    def label_from_instance(self, obj: Model) -> str: ...
+    def label_from_instance(self, obj: _M) -> str: ...
     choices: _PropertyDescriptor[
         _FieldChoices | _ChoicesCallable | CallableChoiceIterator,
         _FieldChoices | CallableChoiceIterator | ModelChoiceIterator,
     ]
     def prepare_value(self, value: Any) -> Any: ...
-    def to_python(self, value: Any | None) -> Model | None: ...
-    def validate(self, value: Model | None) -> None: ...
+    def to_python(self, value: Any | None) -> _M | None: ...
+    def validate(self, value: _M | None) -> None: ...
     def has_changed(self, initial: Model | int | str | UUID | None, data: int | str | None) -> bool: ...
 
-class ModelMultipleChoiceField(ModelChoiceField):
+class ModelMultipleChoiceField(ModelChoiceField[_M]):
     disabled: bool
     empty_label: _StrOrPromise | None
     help_text: _StrOrPromise
     required: bool
     show_hidden_initial: bool
     widget: _ClassLevelWidgetT
     hidden_widget: type[Widget]
-    def __init__(self, queryset: None | Manager[Model] | QuerySet[Model], **kwargs: Any) -> None: ...
-    def to_python(self, value: Any) -> list[Model]: ...  # type: ignore[override]
-    def clean(self, value: Any) -> QuerySet[Model]: ...
+    def __init__(self, queryset: Manager[_M] | QuerySet[_M] | None, **kwargs: Any) -> None: ...
+    def to_python(self, value: Any) -> list[_M]: ...  # type: ignore[override]
+    def clean(self, value: Any) -> QuerySet[_M]: ...
     def prepare_value(self, value: Any) -> Any: ...
     def has_changed(self, initial: Collection[Any] | None, data: Collection[Any] | None) -> bool: ...  # type: ignore[override]
 

ext/django_stubs_ext/patch.py

@@ -16,7 +16,7 @@
 from django.db.models.manager import BaseManager
 from django.db.models.query import QuerySet
 from django.forms.formsets import BaseFormSet
-from django.forms.models import BaseModelForm, BaseModelFormSet
+from django.forms.models import BaseModelForm, BaseModelFormSet, ModelChoiceField
 from django.utils.connection import BaseConnectionHandler
 from django.views.generic.detail import SingleObjectMixin
 from django.views.generic.edit import DeletionMixin, FormMixin
@@ -63,6 +63,7 @@ def __repr__(self) -> str:
     MPGeneric(BaseFormSet),
     MPGeneric(BaseModelForm),
     MPGeneric(BaseModelFormSet),
+    MPGeneric(ModelChoiceField),
     MPGeneric(Feed),
     MPGeneric(Sitemap),
     MPGeneric(SuccessMessageMixin),

tests/typecheck/test_forms.yml

@@ -71,3 +71,44 @@
 
         class SuccessMessageFirstView(FormMixin, SuccessMessageMixin):
             pass
+
+-   case: generic_modelchoicefield_label_from_instance
+    main: |
+        from django import forms
+        from myapp.models import Article, Category
+
+        class ArticleChoiceField(forms.ModelChoiceField[Article]):
+            def label_from_instance(self, obj: Article) -> str:
+                return obj.name
+
+        class BrokenArticleChoiceField(forms.ModelChoiceField[Article]):
+            def label_from_instance(self, obj: Article) -> str:
+                return obj.title # E: "Article" has no attribute "title"  [attr-defined]
+
+        class ArticleMultipleChoiceField(forms.ModelMultipleChoiceField[Article]):
+            def label_from_instance(self, obj: Article) -> str:
+                return obj.name
+
+        class ChooseArticleForm(forms.Form):
+            articles = ArticleMultipleChoiceField(
+                queryset=Article.objects.none(),
+            )
+            best_article = ArticleChoiceField(
+                queryset=Article.objects.none(),
+            )
+            best_category = ArticleChoiceField(
+                queryset=Category.objects.none(), # E: Argument "queryset" to "ArticleChoiceField" has incompatible type "_QuerySet[Category, Category]"; expected "Union[Manager[Article], _QuerySet[Article, Article], None]"  [arg-type]
+            )
+    installed_apps:
+        - myapp
+    files:
+        -   path: myapp/__init__.py
+        -   path: myapp/models.py
+            content: |
+                from django.db import models
+
+                class Category(models.Model):
+                    title = models.CharField(max_length=128)
+
+                class Article(models.Model):
+                    name = models.CharField(max_length=128)