sqlalchemy-oso: handle get_checked_permissions() is None

docs/content/any/project/changelogs/NEXT.md

@@ -49,6 +49,13 @@ oso.query('f(x)', { bindings });
 - Thanks to [`@Kn99HN`](https://github.com/Kn99HN) for adding the
   `acceptExpression` query flag to the Node.js lib!
 
+## `sqlalchemy-oso` `NEW_VERSION`
+
+### Other bugs & improvements
+
+- `scoped_session` now correctly handles a `get_checked_permission` callback that
+  returns `None`.
+
 ## `RELEASED_PACKAGE_1` NEW_VERSION
 
 ### LANGUAGE (e.g., 'Core' or 'Python' or 'Node.js')

languages/python/sqlalchemy-oso/requirements-dev.txt

@@ -1,5 +1,5 @@
-black==21.5b0
+black~=21.12b
 flake8==3.9.2
 mypy==0.812
 sqlalchemy-stubs==0.4
-tox==3.23.1
+tox==3.23.1

languages/python/sqlalchemy-oso/sqlalchemy_oso/session.py

@@ -176,8 +176,9 @@ def scoped_session(
     scopefunc = scopefunc or (lambda: None)
 
     def _scopefunc():
-        checked_permissions = frozenset(get_checked_permissions().items())
-        return (get_oso(), checked_permissions, get_user(), scopefunc())
+        perms = get_checked_permissions()
+        perms = frozenset() if perms is None else frozenset(perms.items())
+        return (get_oso(), perms, get_user(), scopefunc())
 
     factory = authorized_sessionmaker(
         get_oso, get_user, get_checked_permissions, **kwargs

languages/python/sqlalchemy-oso/tests/test_sqlalchemy.py

@@ -215,6 +215,17 @@ def test_authorized_session_relationship(engine, oso, fixture_data):
     assert post_7.created_by is None
 
 
+def test_scoped_session_with_no_checked_permissions(engine, oso, fixture_data):
+    # the policy denies all requests
+    oso.load_str("allow(_, _, _) if false;")
+    # but passing None skips authorization
+    session = scoped_session(lambda: oso, lambda: "user", lambda: None)
+    session.configure(bind=engine)
+    posts = session.query(Post)
+    # check that any posts are allowed
+    assert posts.count()
+
+
 def test_scoped_session_relationship(engine, oso, fixture_data):
     oso.load_str(
         """allow("user", "read", post: Post) if post.id = 1;