Resolve dynamic manager methods through manager MRO (#1701)

This mainly affects reverse managers as we can't inherit dynamic
managers in any other way.

It also renders a manual code path for method name lookup irrelevant as
we can let mypy do that for us.

Author: flaeppe

mypy_django_plugin/transformers/managers.py

@@ -58,10 +58,11 @@ def get_method_type_from_dynamic_manager(
     Attempt to resolve a method on a manager that was built from '.from_queryset'
     """
 
-    manager_type_info = manager_instance.type
+    manager_type_info = manager_instance.type.get_containing_type_info(method_name)
 
     if (
-        "django" not in manager_type_info.metadata
+        manager_type_info is None
+        or "django" not in manager_type_info.metadata
         or "from_queryset_manager" not in manager_type_info.metadata["django"]
     ):
         # Manager isn't dynamically added
@@ -235,45 +236,9 @@ def _replace_type_var(ret_type: MypyType, to_replace: str, replace_by: MypyType)
     return ret_type
 
 
-def get_method_type_from_reverse_manager(
-    api: TypeChecker, method_name: str, manager_type_info: TypeInfo
-) -> Optional[ProperType]:
-    """
-    Attempts to resolve a reverse manager's method via the '_default_manager' manager on the related model
-    From Django docs:
-      "By default the RelatedManager used for reverse relations is a subclass of the default manager for that model."
-    Ref: https://docs.djangoproject.com/en/dev/topics/db/queries/#using-a-custom-reverse-manager
-    """
-    is_reverse_manager = (
-        "django" in manager_type_info.metadata and "related_manager_to_model" in manager_type_info.metadata["django"]
-    )
-    if not is_reverse_manager:
-        return None
-
-    related_model_fullname = manager_type_info.metadata["django"]["related_manager_to_model"]
-    assert isinstance(related_model_fullname, str)
-    model_info = helpers.lookup_fully_qualified_typeinfo(api, related_model_fullname)
-    if model_info is None:
-        return None
-
-    # We should _always_ have a '_default_manager' on a model
-    assert "_default_manager" in model_info.names
-    assert isinstance(model_info.names["_default_manager"].node, Var)
-    manager_instance = model_info.names["_default_manager"].node.type
-    return (
-        get_method_type_from_dynamic_manager(api, method_name, manager_instance)
-        # TODO: Can we assert on None and Instance?
-        if manager_instance is not None and isinstance(manager_instance, Instance)
-        else None
-    )
-
-
 def resolve_manager_method_from_instance(instance: Instance, method_name: str, ctx: AttributeContext) -> MypyType:
     api = helpers.get_typechecker_api(ctx)
-    method_type = get_method_type_from_dynamic_manager(
-        api, method_name, instance
-    ) or get_method_type_from_reverse_manager(api, method_name, instance.type)
-
+    method_type = get_method_type_from_dynamic_manager(api, method_name, instance)
     return method_type if method_type is not None else ctx.default_attr_type
 
 

tests/typecheck/fields/test_related.yml

@@ -642,8 +642,10 @@
         reveal_type(user.article_set) # N: Revealed type is "myapp.models.Article_RelatedManager"
         reveal_type(user.book_set.add)  # N: Revealed type is "def (*objs: Union[myapp.models.Book, builtins.int], *, bulk: builtins.bool =)"
         reveal_type(user.article_set.add)  # N: Revealed type is "def (*objs: Union[myapp.models.Article, builtins.int], *, bulk: builtins.bool =)"
-        reveal_type(user.book_set.filter)  # N: Revealed type is "def (*args: Any, **kwargs: Any) -> myapp.models.LibraryEntityQuerySet[myapp.models.Book]"
-        reveal_type(user.article_set.filter)  # N: Revealed type is "def (*args: Any, **kwargs: Any) -> myapp.models.LibraryEntityQuerySet[myapp.models.Article]"
+        reveal_type(user.book_set.filter)  # N: Revealed type is "def (*args: Any, **kwargs: Any) -> myapp.models.LibraryEntityQuerySet"
+        reveal_type(user.book_set.get())  # N: Revealed type is "myapp.models.Book"
+        reveal_type(user.article_set.filter)  # N: Revealed type is "def (*args: Any, **kwargs: Any) -> myapp.models.LibraryEntityQuerySet"
+        reveal_type(user.article_set.get())  # N: Revealed type is "myapp.models.Article"
         reveal_type(user.book_set.queryset_method())  # N: Revealed type is "builtins.int"
         reveal_type(user.article_set.queryset_method())  # N: Revealed type is "builtins.int"
     installed_apps:
@@ -798,11 +800,13 @@
         from myapp.models.user import User
         reveal_type(Store().purchases)  # N: Revealed type is "myapp.models.purchase.Purchase_RelatedManager"
         reveal_type(Store().purchases.queryset_method())  # N: Revealed type is "myapp.models.querysets.PurchaseQuerySet"
-        reveal_type(Store().purchases.filter())  # N: Revealed type is "myapp.models.querysets.PurchaseQuerySet[myapp.models.purchase.Purchase]"
+        reveal_type(Store().purchases.filter())  # N: Revealed type is "myapp.models.querysets.PurchaseQuerySet"
+        reveal_type(Store().purchases.get())  # N: Revealed type is "myapp.models.purchase.Purchase"
         reveal_type(Store().purchases.filter().queryset_method())  # N: Revealed type is "myapp.models.querysets.PurchaseQuerySet"
         reveal_type(User().purchases)  # N: Revealed type is "myapp.models.purchase.Purchase_RelatedManager"
         reveal_type(User().purchases.queryset_method())  # N: Revealed type is "myapp.models.querysets.PurchaseQuerySet"
-        reveal_type(User().purchases.filter())  # N: Revealed type is "myapp.models.querysets.PurchaseQuerySet[myapp.models.purchase.Purchase]"
+        reveal_type(User().purchases.filter())  # N: Revealed type is "myapp.models.querysets.PurchaseQuerySet"
+        reveal_type(User().purchases.get())  # N: Revealed type is "myapp.models.purchase.Purchase"
         reveal_type(User().purchases.filter().queryset_method())  # N: Revealed type is "myapp.models.querysets.PurchaseQuerySet"
     installed_apps:
         - myapp