Adjust dataclass rules to account for field w/ default

Fixed issue in new ORM dataclasses functionality where dataclass fields on
an abstract base or mixin that contained column or other mapping constructs
would not be mapped if they also included a "default" key within the
dataclasses.field() object.

Fixes: #6093
Change-Id: I628086ceb48ab1dd0702f239cd12be74074f58f1

1 files changed, 17 insertions, 7 deletions

diff --git a/lib/sqlalchemy/orm/decl_base.py b/lib/sqlalchemy/orm/decl_base.py
index a21af192e..0a73288fd 100644
--- a/lib/sqlalchemy/orm/decl_base.py
+++ b/lib/sqlalchemy/orm/decl_base.py
@@ -15,6 +15,7 @@ from sqlalchemy.orm import instrumentation
 from . import clsregistry
 from . import exc as orm_exc
 from . import mapper as mapperlib
+from .attributes import InstrumentedAttribute
 from .attributes import QueryableAttribute
 from .base import _is_mapped_class
 from .base import InspectionAttr
@@ -366,18 +367,24 @@ class _ClassScanMapperConfig(_MapperConfig):
                 elif ret is not absent:
                     return True
 
+                all_field = all_datacls_fields.get(key, absent)
+
                 ret = getattr(cls, key, obj)
 
                 if ret is obj:
                     return False
-                elif ret is not absent:
-                    return True
 
-                ret = all_datacls_fields.get(key, absent)
+                # for dataclasses, this could be the
+                # 'default' of the field.  so filter more specifically
+                # for an already-mapped InstrumentedAttribute
+                if ret is not absent and isinstance(
+                    ret, InstrumentedAttribute
+                ):
+                    return True
 
-                if ret is obj:
+                if all_field is obj:
                     return False
-                elif ret is not absent:
+                elif all_field is not absent:
                     return True
 
                 # can't find another attribute
@@ -401,15 +408,18 @@ class _ClassScanMapperConfig(_MapperConfig):
                     yield name, obj
 
         else:
+            field_names = set()
 
             def local_attributes_for_class():
-                for name, obj in vars(cls).items():
-                    yield name, obj
                 for field in util.local_dataclass_fields(cls):
                     if sa_dataclass_metadata_key in field.metadata:
+                        field_names.add(field.name)
                         yield field.name, field.metadata[
                             sa_dataclass_metadata_key
                         ]
+                for name, obj in vars(cls).items():
+                    if name not in field_names:
+                        yield name, obj
 
         return local_attributes_for_class