From: Kai Mueller <15907922+kasium@users.noreply.github.com>
Date: Tue, 21 Dec 2021 20:00:30 +0000 (-0500)
Subject: Fix missing class attributes when using __class_getitem__
X-Git-Tag: rel_2_0_0b1~586
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1c73759353cdf009c21aa1a56caed574c7d5cf50;p=thirdparty%2Fsqlalchemy%2Fsqlalchemy.git

Fix missing class attributes when using __class_getitem__

Fixed issue where the ``__class_getitem__()`` method of the generated
declarative base class by :func:`_orm.as_declarative` would lead to
inaccessible class attributes such as ``__table__``, for cases where a
``Generic[T]`` style typing declaration were used in the class hierarchy.
This is in continuation from the basic addition of ``__class_getitem__()``
in :ticket:`7368`. Pull request courtesy Kai Mueller.

Fixes: #7462
Closes: #7470
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/7470
Pull-request-sha: d5e5765e0e5542149f116ed9ccff1b3e2e32dee5

Change-Id: I6418af6d34532ff181343884bd419d9c2684e617
---

diff --git a/doc/build/changelog/unreleased_14/7462.rst b/doc/build/changelog/unreleased_14/7462.rst
new file mode 100644
index 0000000000..fa71e1448f
--- /dev/null
+++ b/doc/build/changelog/unreleased_14/7462.rst
@@ -0,0 +1,10 @@
+.. change::
+    :tags: bug, orm, mypy
+    :tickets: 7462, 7368
+
+    Fixed issue where the ``__class_getitem__()`` method of the generated
+    declarative base class by :func:`_orm.as_declarative` would lead to
+    inaccessible class attributes such as ``__table__``, for cases where a
+    ``Generic[T]`` style typing declaration were used in the class hierarchy.
+    This is in continuation from the basic addition of ``__class_getitem__()``
+    in :ticket:`7368`. Pull request courtesy Kai Mueller.
diff --git a/lib/sqlalchemy/orm/decl_api.py b/lib/sqlalchemy/orm/decl_api.py
index ed8617d52f..7b6814863a 100644
--- a/lib/sqlalchemy/orm/decl_api.py
+++ b/lib/sqlalchemy/orm/decl_api.py
@@ -787,8 +787,14 @@ class registry:
         class_dict["__abstract__"] = True
         if mapper:
             class_dict["__mapper_cls__"] = mapper
+
         if hasattr(cls, "__class_getitem__"):
-            class_dict["__class_getitem__"] = cls.__class_getitem__
+
+            def __class_getitem__(cls, key):
+                # allow generic classes in py3.9+
+                return cls
+
+            class_dict["__class_getitem__"] = __class_getitem__
 
         return metaclass(name, bases, class_dict)
 
diff --git a/test/orm/declarative/test_typing_py3k.py b/test/orm/declarative/test_typing_py3k.py
index 823fe54f10..0be91a509f 100644
--- a/test/orm/declarative/test_typing_py3k.py
+++ b/test/orm/declarative/test_typing_py3k.py
@@ -3,9 +3,13 @@ from typing import Type
 from typing import TypeVar
 
 from sqlalchemy import Column
+from sqlalchemy import inspect
 from sqlalchemy import Integer
 from sqlalchemy.orm import as_declarative
+from sqlalchemy.testing import eq_
 from sqlalchemy.testing import fixtures
+from sqlalchemy.testing import is_
+from sqlalchemy.testing.assertions import expect_raises
 
 
 class DeclarativeBaseTest(fixtures.TestBase):
@@ -17,9 +21,22 @@ class DeclarativeBaseTest(fixtures.TestBase):
             def boring(cls: Type[T]) -> Type[T]:
                 return cls
 
+            @classmethod
+            def more_boring(cls: Type[T]) -> int:
+                return 27
+
         @as_declarative()
         class Base(CommonBase[T]):
-            pass
+            foo = 1
 
         class Tab(Base["Tab"]):
+            __tablename__ = "foo"
             a = Column(Integer, primary_key=True)
+
+        eq_(Tab.foo, 1)
+        is_(Tab.__table__, inspect(Tab).local_table)
+        eq_(Tab.boring(), Tab)
+        eq_(Tab.more_boring(), 27)
+
+        with expect_raises(AttributeError):
+            Tab.non_existent