- Added new argument ``include_backrefs=True`` to the

:func:`.validates` function; when set to False, a validation event
will not be triggered if the event was initated as a backref to
an attribute operation from the other side. [ticket:1535]
- break out validation tests into an updated module test_validators

1 files changed, 25 insertions, 6 deletions

diff --git a/lib/sqlalchemy/orm/util.py b/lib/sqlalchemy/orm/util.py
index 1b8f53c9d..b86672175 100644
--- a/lib/sqlalchemy/orm/util.py
+++ b/lib/sqlalchemy/orm/util.py
@@ -70,24 +70,43 @@ class CascadeOptions(frozenset):
         )
 
 
-def _validator_events(desc, key, validator, include_removes):
+def _validator_events(desc, key, validator, include_removes, include_backrefs):
     """Runs a validation method on an attribute value to be set or appended."""
 
+    if not include_backrefs:
+        def detect_is_backref(state, initiator):
+            impl = state.manager[key].impl
+            return initiator.impl is not impl
+
     if include_removes:
         def append(state, value, initiator):
-            return validator(state.obj(), key, value, False)
+            if include_backrefs or not detect_is_backref(state, initiator):
+                return validator(state.obj(), key, value, False)
+            else:
+                return value
 
         def set_(state, value, oldvalue, initiator):
-            return validator(state.obj(), key, value, False)
+            if include_backrefs or not detect_is_backref(state, initiator):
+                return validator(state.obj(), key, value, False)
+            else:
+                return value
 
         def remove(state, value, initiator):
-            validator(state.obj(), key, value, True)
+            if include_backrefs or not detect_is_backref(state, initiator):
+                validator(state.obj(), key, value, True)
+
     else:
         def append(state, value, initiator):
-            return validator(state.obj(), key, value)
+            if include_backrefs or not detect_is_backref(state, initiator):
+                return validator(state.obj(), key, value)
+            else:
+                return value
 
         def set_(state, value, oldvalue, initiator):
-            return validator(state.obj(), key, value)
+            if include_backrefs or not detect_is_backref(state, initiator):
+                return validator(state.obj(), key, value)
+            else:
+                return value
 
     event.listen(desc, 'append', append, raw=True, retval=True)
     event.listen(desc, 'set', set_, raw=True, retval=True)