ensure inherited mapper attrs not interpreted as plain dataclass fields

Fixed issue in new dataclass mapping feature where a column declared on the
decalrative base / abstract base / mixin would leak into the constructor
for an inheriting subclass under some circumstances.

Fixes: #8718
Change-Id: Ic519acf239e2f80541516f10995991cbbbed00bd

2 files changed, 33 insertions, 10 deletions

diff --git a/lib/sqlalchemy/orm/decl_base.py b/lib/sqlalchemy/orm/decl_base.py
index 4e79ecc6f..4e02e589b 100644
--- a/lib/sqlalchemy/orm/decl_base.py
+++ b/lib/sqlalchemy/orm/decl_base.py
@@ -772,7 +772,6 @@ class _ClassScanMapperConfig(_MapperConfig):
                 annotation,
                 is_dataclass_field,
             ) in local_attributes_for_class():
-
                 if re.match(r"^__.+__$", name):
                     if name == "__mapper_args__":
                         check_decl = _check_declared_props_nocascade(
@@ -825,6 +824,7 @@ class _ClassScanMapperConfig(_MapperConfig):
                             "not applying to subclass %s."
                             % (base.__name__, name, base, cls)
                         )
+
                     continue
                 elif base is not cls:
                     # we're a mixin, abstract base, or something that is
@@ -990,10 +990,15 @@ class _ClassScanMapperConfig(_MapperConfig):
             _AttributeOptions._get_arguments_for_make_dataclass(
                 key,
                 anno,
+                mapped_container,
                 self.collected_attributes.get(key, _NoArg.NO_ARG),
             )
-            for key, anno in (
-                (key, mapped_anno if mapped_anno else raw_anno)
+            for key, anno, mapped_container in (
+                (
+                    key,
+                    mapped_anno if mapped_anno else raw_anno,
+                    mapped_container,
+                )
                 for key, (
                     raw_anno,
                     mapped_container,
@@ -1003,7 +1008,6 @@ class _ClassScanMapperConfig(_MapperConfig):
                 ) in self.collected_annotations.items()
             )
         ]
-
         annotations = {}
         defaults = {}
         for item in field_list:
@@ -1139,7 +1143,6 @@ class _ClassScanMapperConfig(_MapperConfig):
         # copy mixin columns to the mapped class
 
         for name, obj, annotation, is_dataclass in attributes_for_class():
-
             if (
                 not fixed_table
                 and obj is None
@@ -1154,14 +1157,16 @@ class _ClassScanMapperConfig(_MapperConfig):
 
             elif isinstance(obj, (Column, MappedColumn)):
 
-                obj = self._collect_annotation(name, annotation, True, obj)
-
                 if attribute_is_overridden(name, obj):
                     # if column has been overridden
                     # (like by the InstrumentedAttribute of the
-                    # superclass), skip
+                    # superclass), skip.  don't collect the annotation
+                    # either (issue #8718)
                     continue
-                elif name not in dict_ and not (
+
+                obj = self._collect_annotation(name, annotation, True, obj)
+
+                if name not in dict_ and not (
                     "__table__" in dict_
                     and (getattr(obj, "name", None) or name)
                     in dict_["__table__"].c
diff --git a/lib/sqlalchemy/orm/interfaces.py b/lib/sqlalchemy/orm/interfaces.py
index 9903c5f4a..1747bfd9b 100644
--- a/lib/sqlalchemy/orm/interfaces.py
+++ b/lib/sqlalchemy/orm/interfaces.py
@@ -213,7 +213,11 @@ class _AttributeOptions(NamedTuple):
 
     @classmethod
     def _get_arguments_for_make_dataclass(
-        cls, key: str, annotation: Type[Any], elem: _T
+        cls,
+        key: str,
+        annotation: Type[Any],
+        mapped_container: Optional[Any],
+        elem: _T,
     ) -> Union[
         Tuple[str, Type[Any]], Tuple[str, Type[Any], dataclasses.Field[Any]]
     ]:
@@ -229,7 +233,21 @@ class _AttributeOptions(NamedTuple):
         elif elem is not _NoArg.NO_ARG:
             # why is typing not erroring on this?
             return (key, annotation, elem)
+        elif mapped_container is not None:
+            # it's Mapped[], but there's no "element", which means declarative
+            # did not actually do anything for this field.  this shouldn't
+            # happen.
+            # previously, this would occur because _scan_attributes would
+            # skip a field that's on an already mapped superclass, but it
+            # would still include it in the annotations, leading
+            # to issue #8718
+
+            assert False, "Mapped[] received without a mapping declaration"
+
         else:
+            # plain dataclass field, not mapped.  Is only possible
+            # if __allow_unmapped__ is set up.  I can see this mode causing
+            # problems...
             return (key, annotation)