Notify when Manager.from_queryset happens inside model class body (#824)

* Refactor to more easily support additional config options

* Notify when Manager.from_queryset happens inside model class body

- A warning will be emitted whenever `Manager.from_queryset` happens
  inside of a model class body

* Resolve generated default manager types before final iteration

A default manager on a model should always exist, eventually. Although,
we extend to look through dynamically generated managers on each
iteration instead of deferring until the final iteration.

mypy_django_plugin/transformers/managers.py

@@ -15,11 +15,12 @@ from mypy.nodes import (
     TypeInfo,
     Var,
 )
-from mypy.plugin import AttributeContext, ClassDefContext, DynamicClassDefContext
+from mypy.plugin import AttributeContext, ClassDefContext, DynamicClassDefContext, MethodContext
 from mypy.types import AnyType, CallableType, Instance, ProperType
 from mypy.types import Type as MypyType
 from mypy.types import TypeOfAny, TypeVarType, UnboundType, get_proper_type
 
+from mypy_django_plugin import errorcodes
 from mypy_django_plugin.lib import fullnames, helpers
 
 
@@ -278,3 +279,20 @@ def create_new_manager_class_from_from_queryset_method(ctx: DynamicClassDefConte
 
     # Insert the new manager (dynamic) class
     assert semanal_api.add_symbol_table_node(ctx.name, SymbolTableNode(GDEF, new_manager_info, plugin_generated=True))
+
+
+def fail_if_manager_type_created_in_model_body(ctx: MethodContext) -> MypyType:
+    """
+    Method hook that checks if method `<Manager>.from_queryset` is called inside a model class body.
+
+    Doing so won't, for instance, trigger the dynamic class hook(`create_new_manager_class_from_from_queryset_method`)
+    for managers.
+    """
+    api = helpers.get_typechecker_api(ctx)
+    outer_model_info = api.scope.active_class()
+    if not outer_model_info or not outer_model_info.has_base(fullnames.MODEL_CLASS_FULLNAME):
+        # Not inside a model class definition
+        return ctx.default_return_type
+
+    api.fail("`.from_queryset` called from inside model class body", ctx.context, code=errorcodes.MANAGER_UNTYPED)
+    return ctx.default_return_type

mypy_django_plugin/transformers/models.py

@@ -280,17 +280,17 @@ class AddDefaultManagerAttribute(ModelClassInitializer):
         try:
             default_manager_info = self.lookup_typeinfo_or_incomplete_defn_error(default_manager_fullname)
         except helpers.IncompleteDefnException as exc:
-            if not self.api.final_iteration:
-                raise exc
-            else:
-                # On final round, see if the default manager is a generated (dynamic class) manager
-                base_manager_fullname = helpers.get_class_fullname(default_manager_cls.__bases__[0])
-                generated_manager_info = self.get_generated_manager_info(
-                    default_manager_fullname, base_manager_fullname
-                )
-                if generated_manager_info is None:
-                    return
-                default_manager_info = generated_manager_info
+            # Check if default manager could be a generated manager
+            base_manager_fullname = helpers.get_class_fullname(default_manager_cls.__bases__[0])
+            generated_manager_info = self.get_generated_manager_info(default_manager_fullname, base_manager_fullname)
+            if generated_manager_info is None:
+                # Manager doesn't appear to be generated. Unless we're on the final round,
+                # see if another round could help figuring out the default manager type
+                if not self.api.final_iteration:
+                    raise exc
+                else:
+                    return None
+            default_manager_info = generated_manager_info
 
         default_manager = Instance(default_manager_info, [Instance(self.model_classdef.info, [])])
         self.add_new_node_to_model_class("_default_manager", default_manager)
@@ -326,10 +326,8 @@ class AddRelatedManagers(ModelClassInitializer):
                     related_manager_info = self.lookup_typeinfo_or_incomplete_defn_error(
                         fullnames.RELATED_MANAGER_CLASS
                     )  # noqa: E501
-                    # TODO: Use default manager instead of 'objects'
-                    # See: https://docs.djangoproject.com/en/dev/topics/db/queries/#using-a-custom-reverse-manager
-                    objects = related_model_info.get("objects")
-                    if not objects:
+                    default_manager = related_model_info.get("_default_manager")
+                    if not default_manager:
                         raise helpers.IncompleteDefnException()
                 except helpers.IncompleteDefnException as exc:
                     if not self.api.final_iteration:
@@ -339,7 +337,7 @@ class AddRelatedManagers(ModelClassInitializer):
 
                 # create new RelatedManager subclass
                 parametrized_related_manager_type = Instance(related_manager_info, [Instance(related_model_info, [])])
-                default_manager_type = objects.type
+                default_manager_type = default_manager.type
                 if default_manager_type is None:
                     default_manager_type = self.try_generate_related_manager(related_model_cls, related_model_info)
                 if (
@@ -360,7 +358,7 @@ class AddRelatedManagers(ModelClassInitializer):
     def try_generate_related_manager(
         self, related_model_cls: Type[Model], related_model_info: TypeInfo
     ) -> Optional[Instance]:
-        manager = related_model_cls._meta.managers_map["objects"]
+        manager = related_model_cls._meta.managers_map["_default_manager"]
         base_manager_fullname = helpers.get_class_fullname(manager.__class__.__bases__[0])
         manager_fullname = helpers.get_class_fullname(manager.__class__)
         generated_managers = self.get_generated_manager_mappings(base_manager_fullname)