accommodate no cls info found in _scan_declarative

Fixed issue in mypy plugin where class info for a custom declarative base
would not be handled correctly on a cached mypy pass, leading to an
AssertionError being raised.

Fixes: #6476
Change-Id: If78340673e6a4d16d8f7cf787ce3bdb02c8bd47b

2 files changed, 6 insertions, 1 deletions

diff --git a/lib/sqlalchemy/ext/mypy/decl_class.py b/lib/sqlalchemy/ext/mypy/decl_class.py
index 2870eeb6f..61737fd66 100644
--- a/lib/sqlalchemy/ext/mypy/decl_class.py
+++ b/lib/sqlalchemy/ext/mypy/decl_class.py
@@ -50,7 +50,10 @@ def _scan_declarative_assignments_and_apply_types(
 
     info = util._info_for_cls(cls, api)
 
-    if cls.fullname.startswith("builtins"):
+    if info is None:
+        # this can occur during cached passes
+        return None
+    elif cls.fullname.startswith("builtins"):
         return None
     elif "_sa_decl_class_applied" in info.metadata:
         cls_metadata = util.DeclClassApplied.deserialize(
diff --git a/lib/sqlalchemy/ext/mypy/util.py b/lib/sqlalchemy/ext/mypy/util.py
index 26bb0ac67..67c3fa209 100644
--- a/lib/sqlalchemy/ext/mypy/util.py
+++ b/lib/sqlalchemy/ext/mypy/util.py
@@ -208,6 +208,8 @@ def _info_for_cls(
 ) -> TypeInfo:
     if cls.info is CLASSDEF_NO_INFO:
         sym = api.lookup_qualified(cls.name, cls)
+        if sym is None:
+            return None
         assert sym and isinstance(sym.node, TypeInfo)
         return sym.node