add plugin support for ArrayField base_field

django-stubs-generated/contrib/postgres/fields/array.pyi

@@ -19,7 +19,7 @@ class ArrayField(CheckFieldDefaultMixin, Field, Generic[_T]):
     from_db_value: Any = ...
 
     def __init__(
-        self, base_field: _T, size: None = ..., **kwargs: Any
+        self, base_field: Field, size: None = ..., **kwargs: Any
     ) -> None: ...
     @property
     def model(self): ...

django-stubs/contrib/postgres/fields/array.pyi

@@ -1,11 +1,14 @@
-from typing import List, Any
+from typing import List, Any, TypeVar, Generic
 
 from django.contrib.postgres.fields.mixins import CheckFieldDefaultMixin
 from django.db.models import Field
 
+_T = TypeVar('_T', bound=Field)
 
-class ArrayField(CheckFieldDefaultMixin, Field):
+
+class ArrayField(CheckFieldDefaultMixin, Field, Generic[_T]):
     def __init__(self,
                  base_field: Field,
                  **kwargs): ...
-    def __get__(self, instance, owner) -> List[Any]: ...
+
+    def __get__(self, instance, owner) -> List[_T]: ...

mypy_django_plugin/plugins/postgres_fields.py

@@ -1,14 +1,24 @@
-from mypy.plugin import Plugin, ClassDefContext
+from typing import Optional, Callable
+
+from mypy.plugin import Plugin, FunctionContext
+from mypy.types import Type
 
 
-def determine_type_of_array_field(context: ClassDefContext) -> None:
-    pass
+def determine_type_of_array_field(ctx: FunctionContext) -> Type:
+    assert 'base_field' in ctx.context.arg_names
+    base_field_arg_index = ctx.context.arg_names.index('base_field')
+    base_field_arg_type = ctx.arg_types[base_field_arg_index][0]
+
+    return ctx.api.named_generic_type(ctx.context.callee.fullname,
+                                      args=[base_field_arg_type.type.names['__get__'].type.ret_type])
 
 
 class PostgresFieldsPlugin(Plugin):
-    def get_base_class_hook(self, fullname: str
-                            ):
+    def get_function_hook(self, fullname: str
+                          ) -> Optional[Callable[[FunctionContext], Type]]:
+        if fullname == 'django.contrib.postgres.fields.array.ArrayField':
             return determine_type_of_array_field
+        return None
 
 
 def plugin(version):

test/test-data/check-postgres-fields.test

@@ -7,7 +7,9 @@ from django.contrib.postgres.fields import ArrayField
 
 class User(models.Model):
     members = ArrayField(base_field=models.IntegerField())
+    members_as_text = ArrayField(base_field=models.CharField(max_length=255))
 
 user = User()
-reveal_type(user.members)  # E: Revealed type is 'typing.List[int]'
+reveal_type(user.members)  # E: Revealed type is 'builtins.list[builtins.int*]'
+reveal_type(user.members_as_text)  # E: Revealed type is 'builtins.list[builtins.str*]'
 [out]