support adapt_on_names for with_polymorphic

Added :paramref:`_orm.with_polymorphic.adapt_on_names` to the
:func:`_orm.with_polymorphic` function, which allows a polymorphic load
(typically with concrete mapping) to be stated against an alternative
selectable that will adapt to the original mapped selectable on column
names alone.

Fixes: #7805
Change-Id: I933e180a489fec8a6f4916d1622d444dd4434f30

2 files changed, 16 insertions, 1 deletions

diff --git a/lib/sqlalchemy/orm/_orm_constructors.py b/lib/sqlalchemy/orm/_orm_constructors.py
index 8e05c6ef2..8d5fb91d0 100644
--- a/lib/sqlalchemy/orm/_orm_constructors.py
+++ b/lib/sqlalchemy/orm/_orm_constructors.py
@@ -2110,6 +2110,7 @@ def with_polymorphic(
     flat=False,
     polymorphic_on=None,
     aliased=False,
+    adapt_on_names=False,
     innerjoin=False,
     _use_mapper_path=False,
 ):
@@ -2173,6 +2174,15 @@ def with_polymorphic(
 
     :param innerjoin: if True, an INNER JOIN will be used.  This should
        only be specified if querying for one specific subtype only
+
+    :param adapt_on_names: Passes through the
+      :paramref:`_orm.aliased.adapt_on_names`
+      parameter to the aliased object.  This may be useful in situations where
+      the given selectable is not directly related to the existing mapped
+      selectable.
+
+      .. versionadded:: 1.4.33
+
     """
     return AliasedInsp._with_polymorphic_factory(
         base,
@@ -2180,6 +2190,7 @@ def with_polymorphic(
         selectable=selectable,
         flat=flat,
         polymorphic_on=polymorphic_on,
+        adapt_on_names=adapt_on_names,
         aliased=aliased,
         innerjoin=innerjoin,
         _use_mapper_path=_use_mapper_path,
diff --git a/lib/sqlalchemy/orm/util.py b/lib/sqlalchemy/orm/util.py
index e00e05954..d4faf10e3 100644
--- a/lib/sqlalchemy/orm/util.py
+++ b/lib/sqlalchemy/orm/util.py
@@ -757,7 +757,9 @@ class AliasedInsp(
             # are not even the thing we are mapping, such as embedded
             # selectables in subqueries or CTEs.  See issue #6060
             adapt_from_selectables=[
-                m.selectable for m in self.with_polymorphic_mappers
+                m.selectable
+                for m in self.with_polymorphic_mappers
+                if not adapt_on_names
             ],
         )
 
@@ -810,6 +812,7 @@ class AliasedInsp(
         polymorphic_on=None,
         aliased=False,
         innerjoin=False,
+        adapt_on_names=False,
         _use_mapper_path=False,
     ):
 
@@ -830,6 +833,7 @@ class AliasedInsp(
             base,
             selectable,
             with_polymorphic_mappers=mappers,
+            adapt_on_names=adapt_on_names,
             with_polymorphic_discriminator=polymorphic_on,
             use_mapper_path=_use_mapper_path,
             represents_outer_join=not innerjoin,