use field annotations for values_list types (typeddjango#2248) (#20)

Co-authored-by: Anthony Sottile <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

mypy_django_plugin/django/context.py

@@ -91,6 +91,35 @@ class LookupsAreUnsupported(Exception):
     pass
 
 
+def _get_field_type_from_model_type_info(info: Optional[TypeInfo], field_name: str) -> Optional[Instance]:
+    if info is None:
+        return None
+    field_node = info.get(field_name)
+    if field_node is None or not isinstance(field_node.type, Instance):
+        return None
+    # Field declares a set and a get type arg. Fallback to `None` when we can't find any args
+    elif len(field_node.type.args) != 2:
+        return None
+    else:
+        return field_node.type
+
+
+def _get_field_set_type_from_model_type_info(info: Optional[TypeInfo], field_name: str) -> Optional[MypyType]:
+    field_type = _get_field_type_from_model_type_info(info, field_name)
+    if field_type is not None:
+        return field_type.args[0]
+    else:
+        return None
+
+
+def _get_field_get_type_from_model_type_info(info: Optional[TypeInfo], field_name: str) -> Optional[MypyType]:
+    field_type = _get_field_type_from_model_type_info(info, field_name)
+    if field_type is not None:
+        return field_type.args[1]
+    else:
+        return None
+
+
 class DjangoContext:
     def __init__(self, django_settings_module: str) -> None:
         self.django_settings_module = django_settings_module
@@ -152,13 +181,13 @@ def get_field_lookup_exact_type(
     ) -> MypyType:
         if isinstance(field, (RelatedField, ForeignObjectRel)):
             related_model_cls = self.get_field_related_model_cls(field)
-            primary_key_field = self.get_primary_key_field(related_model_cls)
-            primary_key_type = self.get_field_get_type(api, primary_key_field, method="init")
-
             rel_model_info = helpers.lookup_class_typeinfo(api, related_model_cls)
             if rel_model_info is None:
                 return AnyType(TypeOfAny.explicit)
 
+            primary_key_field = self.get_primary_key_field(related_model_cls)
+            primary_key_type = self.get_field_get_type(api, rel_model_info, primary_key_field, method="init")
+
             model_and_primary_key_type = UnionType.make_union([Instance(rel_model_info, []), primary_key_type])
             return helpers.make_optional(model_and_primary_key_type)
 
@@ -200,19 +229,6 @@ def get_expected_types(self, api: TypeChecker, model_cls: Type[Model], *, method
             field_set_type = self.get_field_set_type(api, primary_key_field, method=method)
             expected_types["pk"] = field_set_type
 
-        def get_field_set_type_from_model_type_info(info: Optional[TypeInfo], field_name: str) -> Optional[MypyType]:
-            if info is None:
-                return None
-            field_node = info.get(field_name)
-            if field_node is None or not isinstance(field_node.type, Instance):
-                return None
-            elif not field_node.type.args:
-                # Field declares a set and a get type arg. Fallback to `None` when we can't find any args
-                return None
-
-            set_type = field_node.type.args[0]
-            return set_type
-
         model_info = helpers.lookup_class_typeinfo(api, model_cls)
         for field in model_cls._meta.get_fields():
             if isinstance(field, Field):
@@ -223,7 +239,7 @@ def get_field_set_type_from_model_type_info(info: Optional[TypeInfo], field_name
                 # Try to retrieve set type from a model's TypeInfo object and fallback to retrieving it manually
                 # from django-stubs own declaration. This is to align with the setter types declared for
                 # assignment.
-                field_set_type = get_field_set_type_from_model_type_info(
+                field_set_type = _get_field_set_type_from_model_type_info(
                     model_info, field_name
                 ) or self.get_field_set_type(api, field, method=method)
                 expected_types[field_name] = field_set_type
@@ -340,20 +356,31 @@ def get_field_set_type(
         return field_set_type
 
     def get_field_get_type(
-        self, api: TypeChecker, field: Union["Field[Any, Any]", ForeignObjectRel], *, method: str
+        self,
+        api: TypeChecker,
+        model_info: Optional[TypeInfo],
+        field: Union["Field[Any, Any]", ForeignObjectRel],
+        *,
+        method: str,
     ) -> MypyType:
         """Get a type of __get__ for this specific Django field."""
+        if isinstance(field, Field):
+            get_type = _get_field_get_type_from_model_type_info(model_info, field.attname)
+            if get_type is not None:
+                return get_type
+
         field_info = helpers.lookup_class_typeinfo(api, field.__class__)
         if field_info is None:
             return AnyType(TypeOfAny.unannotated)
 
         is_nullable = self.get_field_nullability(field, method)
         if isinstance(field, RelatedField):
             related_model_cls = self.get_field_related_model_cls(field)
+            rel_model_info = helpers.lookup_class_typeinfo(api, related_model_cls)
 
             if method in ("values", "values_list"):
                 primary_key_field = self.get_primary_key_field(related_model_cls)
-                return self.get_field_get_type(api, primary_key_field, method=method)
+                return self.get_field_get_type(api, rel_model_info, primary_key_field, method=method)
 
             model_info = helpers.lookup_class_typeinfo(api, related_model_cls)
             if model_info is None:

mypy_django_plugin/transformers/querysets.py

@@ -66,10 +66,12 @@ def get_field_type_from_lookup(
     elif (isinstance(lookup_field, RelatedField) and lookup_field.column == lookup) or isinstance(
         lookup_field, ForeignObjectRel
     ):
-        related_model_cls = django_context.get_field_related_model_cls(lookup_field)
-        lookup_field = django_context.get_primary_key_field(related_model_cls)
+        model_cls = django_context.get_field_related_model_cls(lookup_field)
+        lookup_field = django_context.get_primary_key_field(model_cls)
 
-    field_get_type = django_context.get_field_get_type(helpers.get_typechecker_api(ctx), lookup_field, method=method)
+    api = helpers.get_typechecker_api(ctx)
+    model_info = helpers.lookup_class_typeinfo(api, model_cls)
+    field_get_type = django_context.get_field_get_type(api, model_info, lookup_field, method=method)
     return field_get_type
 
 
@@ -87,6 +89,7 @@ def get_values_list_row_type(
         return AnyType(TypeOfAny.from_error)
 
     typechecker_api = helpers.get_typechecker_api(ctx)
+    model_info = helpers.lookup_class_typeinfo(typechecker_api, model_cls)
     if len(field_lookups) == 0:
         if flat:
             primary_key_field = django_context.get_primary_key_field(model_cls)
@@ -98,7 +101,9 @@ def get_values_list_row_type(
         elif named:
             column_types: OrderedDict[str, MypyType] = OrderedDict()
             for field in django_context.get_model_fields(model_cls):
-                column_type = django_context.get_field_get_type(typechecker_api, field, method="values_list")
+                column_type = django_context.get_field_get_type(
+                    typechecker_api, model_info, field, method="values_list"
+                )
                 column_types[field.attname] = column_type
             if is_annotated:
                 # Return a NamedTuple with a fallback so that it's possible to access any field

tests/typecheck/managers/querysets/test_values_list.yml

@@ -47,6 +47,26 @@
                     name = models.CharField(max_length=100)
                     age = models.IntegerField()
 
+-   case: values_list_types_are_field_types
+    main: |
+        from myapp.models import Concrete
+        ret = list(Concrete.objects.values_list('id', 'data'))
+        reveal_type(ret)  # N: Revealed type is "builtins.list[Tuple[builtins.int, builtins.dict[builtins.str, builtins.str]]]"
+    installed_apps:
+        - myapp
+    files:
+        -   path: myapp/__init__.py
+        -   path: myapp/models.py
+            content: |
+                from __future__ import annotations
+                from django.db import models
+
+                class JSONField(models.TextField): pass  # incomplete
+
+                class Concrete(models.Model):
+                    id = models.IntegerField()
+                    data: models.Field[dict[str, str], dict[str, str]] = JSONField()
+
 -   case: values_list_supports_queryset_methods
     main: |
         from myapp.models import MyUser