Fixes for uselist=True with m2o relationships

Fixed bug where a many-to-one relationship that specified ``uselist=True``
would fail to update correctly during a primary key change where a related
column needs to change.

Fixed bug where the detection for many-to-one or one-to-one use with a
"dynamic" relationship, which is an invalid configuration, would fail to
raise if the relationship were configured with ``uselist=True``.  The
current fix is that it warns, instead of raises, as this would otherwise be
backwards incompatible, however in a future release it will be a raise.

Fixes: #4772
Change-Id: Ibd5d2f7329ff245c88118e2533fc8ef42a09fef3

1 files changed, 4 insertions, 2 deletions

diff --git a/lib/sqlalchemy/testing/entities.py b/lib/sqlalchemy/testing/entities.py
index b894979d0..cbc7a2fd5 100644
--- a/lib/sqlalchemy/testing/entities.py
+++ b/lib/sqlalchemy/testing/entities.py
@@ -7,7 +7,7 @@
 
 import sqlalchemy as sa
 from .. import exc as sa_exc
-
+from ..util import compat
 
 _repr_stack = set()
 
@@ -90,7 +90,9 @@ class ComparableEntity(BasicEntity):
                 except (AttributeError, sa_exc.UnboundExecutionError):
                     return False
 
-                if hasattr(value, "__iter__"):
+                if hasattr(value, "__iter__") and not isinstance(
+                    value, compat.string_types
+                ):
                     if hasattr(value, "__getitem__") and not hasattr(
                         value, "keys"
                     ):