Fix error with null=True and Any type param for Field types (#2492)

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

Author: sobolevn

mypy_django_plugin/transformers/fields.py

@@ -166,11 +166,11 @@ def set_descriptor_types_for_field(
     if not (isinstance(mapped_set_type, UninhabitedType) or isinstance(mapped_get_type, UninhabitedType)):
         # always replace set_type and get_type with (non-Any) mapped types
         set_type = helpers.convert_any_to_type(mapped_set_type, set_type)
-        get_type = helpers.convert_any_to_type(mapped_get_type, get_type)
+        get_type = get_proper_type(helpers.convert_any_to_type(mapped_get_type, get_type))
 
         # the get_type must be optional if the field is nullable
         if (is_get_nullable or is_nullable) and not (
-            isinstance(get_proper_type(get_type), NoneType) or helpers.is_optional(get_type)
+            isinstance(get_type, NoneType) or helpers.is_optional(get_type) or isinstance(get_type, AnyType)
         ):
             ctx.api.fail(
                 f"{default_return_type.type.name} is nullable but its generic get type parameter is not optional",

tests/typecheck/fields/test_custom_fields.yml

@@ -18,13 +18,12 @@
         reveal_type(user.my_custom_field13)  # N: Revealed type is "Union[myapp.models.CustomFieldValue, None]"
         reveal_type(user.my_custom_field14)  # N: Revealed type is "Union[builtins.bool, None]"
         reveal_type(user.my_custom_field15)  # N: Revealed type is "None"
+
+        reveal_type(user.my_custom_field_any1)  # N: Revealed type is "Any"
+        reveal_type(user.my_custom_field_any2)  # N: Revealed type is "Any"
+        reveal_type(user.my_custom_field_any3)  # N: Revealed type is "Any"
+        reveal_type(user.my_custom_field_any4)  # N: Revealed type is "Any"
     monkeypatch: true
-    out: |
-      myapp/models:31: error: GenericField is nullable but its generic get type parameter is not optional  [misc]
-      myapp/models:32: error: CustomValueField is nullable but its generic get type parameter is not optional  [misc]
-      myapp/models:33: error: SingleTypeField is nullable but its generic get type parameter is not optional  [misc]
-      myapp/models:34: error: AdditionalTypeVarField is nullable but its generic get type parameter is not optional  [misc]
-      myapp/models:35: error: Field is nullable but its generic get type parameter is not optional  [misc]
     installed_apps:
         - myapp
     files:
@@ -53,19 +52,24 @@
 
                 class CustomSmallIntegerField(fields.SmallIntegerField[_ST, _GT]): ...
 
+                class FieldImplicitAny(fields.Field): ...
+                class FieldExplicitAny(fields.Field[Any, Any]): ...
+
                 class User(models.Model):
                     id = models.AutoField(primary_key=True)
                     my_custom_field1 = GenericField[Union[CustomFieldValue, int], CustomFieldValue]()
                     my_custom_field2 = CustomValueField()
                     my_custom_field3 = SingleTypeField[bool]()
                     my_custom_field4 = AdditionalTypeVarField[Union[CustomFieldValue, int], CustomFieldValue, bool]()
+                    my_custom_field_any1 = FieldImplicitAny()
+                    my_custom_field_any2 = FieldExplicitAny()
 
                     # test null=True on fields with non-optional generic types throw error
-                    my_custom_field5 = GenericField[Union[CustomFieldValue, int], CustomFieldValue](null=True)
-                    my_custom_field6 = CustomValueField(null=True)
-                    my_custom_field7 = SingleTypeField[bool](null=True)
-                    my_custom_field8 = AdditionalTypeVarField[Union[CustomFieldValue, int], CustomFieldValue, bool](null=True)
-                    my_custom_field9 = fields.Field[Union[CustomFieldValue, int], CustomFieldValue](null=True)
+                    my_custom_field5 = GenericField[Union[CustomFieldValue, int], CustomFieldValue](null=True)  # E: GenericField is nullable but its generic get type parameter is not optional  [misc]
+                    my_custom_field6 = CustomValueField(null=True)  # E: CustomValueField is nullable but its generic get type parameter is not optional  [misc]
+                    my_custom_field7 = SingleTypeField[bool](null=True)  # E: SingleTypeField is nullable but its generic get type parameter is not optional  [misc]
+                    my_custom_field8 = AdditionalTypeVarField[Union[CustomFieldValue, int], CustomFieldValue, bool](null=True)  # E: AdditionalTypeVarField is nullable but its generic get type parameter is not optional  [misc]
+                    my_custom_field9 = fields.Field[Union[CustomFieldValue, int], CustomFieldValue](null=True)  # E: Field is nullable but its generic get type parameter is not optional  [misc]
 
                     # test overriding fields that set _pyi_private_set_type or _pyi_private_get_type
                     my_custom_field10 = fields.SmallIntegerField[bool, bool]()
@@ -76,3 +80,7 @@
                     my_custom_field13 = GenericField[Union[CustomFieldValue, int], Union[CustomFieldValue, None]](null=True)
                     my_custom_field14 = SingleTypeField[Union[bool, None]](null=True)
                     my_custom_field15 = fields.Field[None, None](null=True)
+
+                    # test null=True on Any does not raise
+                    my_custom_field_any3 = FieldImplicitAny(null=True)
+                    my_custom_field_any4 = FieldExplicitAny(null=True)