Expand sibling tests for overlaps warning

Scaled back the warning message added in :ticket:`5171` to not warn for
overlapping columns in an inheritance scenario where a particular
relationship is local to a subclass and therefore does not represent an
overlap.

Add errors documentation for the warning and also expand
``util.warn()`` to include a code parameter.

Fixes: #6171
Change-Id: Icb1f12d8d645d439ffd2bbb7371c6b00042b6ae3

2 files changed, 12 insertions, 2 deletions

diff --git a/lib/sqlalchemy/orm/relationships.py b/lib/sqlalchemy/orm/relationships.py
index c1fcc63c1..2ed9d859a 100644
--- a/lib/sqlalchemy/orm/relationships.py
+++ b/lib/sqlalchemy/orm/relationships.py
@@ -364,6 +364,10 @@ class RelationshipProperty(StrategizedProperty):
 
            .. versionadded:: 1.4
 
+           .. seealso::
+
+                :ref:`error_qzyx` - usage example
+
         :param bake_queries=True:
           Use the :class:`.BakedQuery` cache to cache the construction of SQL
           used in lazy loads.  True by default.   Set to False if the
@@ -3423,6 +3427,8 @@ class JoinCondition(object):
                         and self.prop.key not in pr._overlaps
                         and not self.prop.parent.is_sibling(pr.parent)
                         and not self.prop.mapper.is_sibling(pr.mapper)
+                        and not self.prop.parent.is_sibling(pr.mapper)
+                        and not self.prop.mapper.is_sibling(pr.parent)
                         and (
                             self.prop.key != pr.key
                             or not self.prop.parent.common_parent(pr.parent)
@@ -3453,7 +3459,8 @@ class JoinCondition(object):
                                 "'%s' (copies %s to %s)" % (pr, fr_, to_)
                                 for (pr, fr_) in other_props
                             ),
-                        )
+                        ),
+                        code="qzyx",
                     )
                 self._track_overlapping_sync_targets[to_][self.prop] = from_
 
diff --git a/lib/sqlalchemy/util/langhelpers.py b/lib/sqlalchemy/util/langhelpers.py
index 51b9071d5..b31f316fe 100644
--- a/lib/sqlalchemy/util/langhelpers.py
+++ b/lib/sqlalchemy/util/langhelpers.py
@@ -1604,13 +1604,16 @@ class _hash_limit_string(compat.text_type):
         return hash(self) == hash(other)
 
 
-def warn(msg):
+def warn(msg, code=None):
     """Issue a warning.
 
     If msg is a string, :class:`.exc.SAWarning` is used as
     the category.
 
     """
+    if code:
+        msg = "%s %s" % (msg, exc.SQLAlchemyError(msg, code=code)._code_str())
+
     warnings.warn(msg, exc.SAWarning, stacklevel=2)