Add support for inline from_queryset in model classes (#1045)

* Add support for inline from_queryset in model classes

This adds support for calling <Manager>.from_queryset(<QuerySet>)()
inline in models, for example like this:

    class MyModel(models.Model):
        objects = MyManager.from_queryset(MyQuerySet)()

This is done by inspecting the class body in the transform_class_hook

* Fix missing methods on copied manager

* Add test and other minor tweaks

* Always create manager at module level

When the manager is added at the class level, which happened when it was
created inline in the model body, it's not possible to retrieve the
manager again based on fullname. That lead to problems with inheritance
and the default manager.

tests/typecheck/fields/test_related.yml

@@ -678,7 +678,6 @@
                     def custom(self) -> None:
                         pass
 
-                # Note, that we cannot resolve dynamic calls for custom managers:
                 class Transaction(models.Model):
                     objects = BaseManager.from_queryset(TransactionQuerySet)
                     def test(self) -> None:
@@ -689,9 +688,8 @@
                 class TransactionLog(models.Model):
                     transaction = models.ForeignKey(Transaction, on_delete=models.CASCADE)
     out: |
-        myapp/models:9: error: `.from_queryset` called from inside model class body
-        myapp/models:11: note: Revealed type is "django.db.models.manager.RelatedManager[myapp.models.TransactionLog]"
-        myapp/models:13: note: Revealed type is "Any"
+        myapp/models:10: note: Revealed type is "django.db.models.manager.RelatedManager[myapp.models.TransactionLog]"
+        myapp/models:12: note: Revealed type is "Any"
 
 
 -   case: resolve_primary_keys_for_foreign_keys_with_abstract_self_model

tests/typecheck/managers/querysets/test_from_queryset.yml

@@ -359,12 +359,17 @@
                 class MyModel(models.Model):
                     objects = NewManager()
 
--   case: from_queryset_in_model_class_body_yields_message
+-   case: test_queryset_in_model_class_body
     main: |
         from myapp.models import MyModel
-        reveal_type(MyModel.base_manager)  # N: Revealed type is "myapp.models.BaseManagerFromMyQuerySet[myapp.models.MyModel]"
-        reveal_type(MyModel.manager)  # N: Revealed type is "myapp.models.ManagerFromMyQuerySet[myapp.models.MyModel]"
-        reveal_type(MyModel.custom_manager)  # N: Revealed type is "myapp.models.MyManagerFromMyQuerySet[myapp.models.MyModel]"
+        reveal_type(MyModel.objects)  # N: Revealed type is "myapp.models.MyManagerFromMyQuerySet[myapp.models.MyModel]"
+        reveal_type(MyModel._default_manager)  # N: Revealed type is "myapp.models.MyManagerFromMyQuerySet[myapp.models.MyModel]"
+        reveal_type(MyModel.objects.all)  # N: Revealed type is "def () -> myapp.models.MyQuerySet[myapp.models.MyModel]"
+        reveal_type(MyModel.objects.custom)  # N: Revealed type is "def () -> myapp.models.MyQuerySet"
+        reveal_type(MyModel.objects.all().filter)  # N: Revealed type is "def (*args: Any, **kwargs: Any) -> myapp.models.MyQuerySet[myapp.models.MyModel]"
+        reveal_type(MyModel.objects.custom().filter)  # N: Revealed type is "def (*args: Any, **kwargs: Any) -> myapp.models.MyQuerySet"
+        reveal_type(MyModel.objects2)  # N: Revealed type is "myapp.models.MyManagerFromMyQuerySet[myapp.models.MyModel]"
+        reveal_type(MyModel._default_manager)  # N: Revealed type is "myapp.models.MyManagerFromMyQuerySet[myapp.models.MyModel]"
     installed_apps:
         - myapp
     files:
@@ -372,29 +377,42 @@
         -   path: myapp/models.py
             content: |
                 from django.db import models
-                from django.db.models.manager import BaseManager
+
+                class MyManager(models.Manager["MyModel"]):
+                    pass
 
                 class MyQuerySet(models.QuerySet["MyModel"]):
-                    def queryset_method(self) -> int:
-                        return 1
+                    def custom(self) -> "MyQuerySet":
+                        pass
 
-                class MyManager(BaseManager):
-                    ...
-
-                BaseManagerFromMyQuerySet = BaseManager.from_queryset(MyQuerySet)
-                ManagerFromMyQuerySet = models.Manager.from_queryset(MyQuerySet)
-                MyManagerFromMyQuerySet = MyManager.from_queryset(MyQuerySet)
                 class MyModel(models.Model):
-                    objects1 = BaseManager.from_queryset(MyQuerySet)()  # E: `.from_queryset` called from inside model class body
-                    objects2 = BaseManager.from_queryset(MyQuerySet)  # E: `.from_queryset` called from inside model class body
-                    objects3 = models.Manager.from_queryset(MyQuerySet)()  # E: `.from_queryset` called from inside model class body
-                    objects4 = models.Manager.from_queryset(MyQuerySet)  # E: `.from_queryset` called from inside model class body
-                    objects5 = MyManager.from_queryset(MyQuerySet)  # E: `.from_queryset` called from inside model class body
-                    objects6 = MyManager.from_queryset(MyQuerySet)()  # E: `.from_queryset` called from inside model class body
-                    # Initiating the manager type is fine
-                    base_manager = BaseManagerFromMyQuerySet()
-                    manager = ManagerFromMyQuerySet()
-                    custom_manager = MyManagerFromMyQuerySet()
+                    objects = MyManager.from_queryset(MyQuerySet)()
+                    objects2 = MyManager.from_queryset(MyQuerySet)()
+
+-   case: test_queryset_in_model_class_body_subclass
+    main: |
+        from myapp.models import MyModel
+        reveal_type(MyModel.objects)  # N: Revealed type is "myapp.models.BaseManagerFromBaseQuerySet[myapp.models.MyModel]"
+    installed_apps:
+        - myapp
+    files:
+        -   path: myapp/__init__.py
+        -   path: myapp/models.py
+            content: |
+                from django.db import models
+
+                class BaseManager(models.Manager["BaseModel"]):
+                    pass
+
+                class BaseQuerySet(models.QuerySet["BaseModel"]):
+                    def custom(self) -> "BaseQuerySet":
+                        pass
+
+                class BaseModel(models.Model):
+                    objects = BaseManager.from_queryset(BaseQuerySet)()
+
+                class MyModel(BaseModel):
+                    pass
 
 -   case: from_queryset_includes_methods_returning_queryset
     main: |

tests/typecheck/managers/test_managers.yml

@@ -332,14 +332,14 @@
 -   case: custom_manager_returns_proper_model_types
     main: |
         from myapp.models import User
-        reveal_type(User.objects)  # N: Revealed type is "myapp.models.User_MyManager2[myapp.models.User]"
+        reveal_type(User.objects)  # N: Revealed type is "myapp.models.User_MyManager[myapp.models.User]"
         reveal_type(User.objects.select_related())  # N: Revealed type is "django.db.models.query._QuerySet[myapp.models.User, myapp.models.User]"
         reveal_type(User.objects.get())  # N: Revealed type is "myapp.models.User"
         reveal_type(User.objects.get_instance())  # N: Revealed type is "builtins.int"
         reveal_type(User.objects.get_instance_untyped('hello'))  # N: Revealed type is "Any"
 
         from myapp.models import ChildUser
-        reveal_type(ChildUser.objects)  # N: Revealed type is "myapp.models.ChildUser_MyManager2[myapp.models.ChildUser]"
+        reveal_type(ChildUser.objects)  # N: Revealed type is "myapp.models.ChildUser_MyManager[myapp.models.ChildUser]"
         reveal_type(ChildUser.objects.select_related())  # N: Revealed type is "django.db.models.query._QuerySet[myapp.models.ChildUser, myapp.models.ChildUser]"
         reveal_type(ChildUser.objects.get())  # N: Revealed type is "myapp.models.ChildUser"
         reveal_type(ChildUser.objects.get_instance())  # N: Revealed type is "builtins.int"