From 65e16e9b3e9ceabfbf3f11fbefa498109d8b335a Mon Sep 17 00:00:00 2001
From: Mike Bayer <mike_mp@zzzcomputing.com>
Date: Fri, 25 Jun 2021 16:51:50 -0400
Subject: have automap suppress overlaps warning for mapped secondary

Fixed regression in :mod:`sqlalchemy.ext.automap` extension such that the
use case of creating an explicit mapped class to a table that is also the
:paramref:`_orm.relationship.secondary` element of a
:func:`_orm.relationship` that automap will be generating would emit the
"overlaps" warnings introduced in 1.4 and discussed at :ref:`error_qzyx`.
While generating this case from automap is still subject to the same
caveats that the "overlaps" warning refers towards, as automap is intended
for more ad-hoc use cases, the condition which produces the warning is
disabled when a many-to-many relationship with this particular pattern is
generated.

Fixes: #6679
Change-Id: Ib3a53982b076ed4999b0d3235f84008b9e2f1cce
---
 lib/sqlalchemy/ext/automap.py       | 9 +++++++++
 lib/sqlalchemy/orm/relationships.py | 8 ++++++++
 2 files changed, 17 insertions(+)

(limited to 'lib')

diff --git a/lib/sqlalchemy/ext/automap.py b/lib/sqlalchemy/ext/automap.py
index e20435911..8b75dce7b 100644
--- a/lib/sqlalchemy/ext/automap.py
+++ b/lib/sqlalchemy/ext/automap.py
@@ -1153,6 +1153,11 @@ def _m2m_relationship(
 
     create_backref = backref_name not in referred_cfg.properties
 
+    if table in table_to_map_config:
+        overlaps = "__*"
+    else:
+        overlaps = None
+
     if relationship_name not in map_config.properties:
         if create_backref:
             backref_obj = generate_relationship(
@@ -1163,9 +1168,11 @@ def _m2m_relationship(
                 referred_cls,
                 local_cls,
                 collection_class=collection_class,
+                overlaps=overlaps,
             )
         else:
             backref_obj = None
+
         rel = generate_relationship(
             automap_base,
             interfaces.MANYTOMANY,
@@ -1173,6 +1180,7 @@ def _m2m_relationship(
             relationship_name,
             local_cls,
             referred_cls,
+            overlaps=overlaps,
             secondary=table,
             primaryjoin=and_(
                 fk.column == fk.parent for fk in m2m_const[0].elements
@@ -1198,6 +1206,7 @@ def _m2m_relationship(
             backref_name,
             referred_cls,
             local_cls,
+            overlaps=overlaps,
             secondary=table,
             primaryjoin=and_(
                 fk.column == fk.parent for fk in m2m_const[1].elements
diff --git a/lib/sqlalchemy/orm/relationships.py b/lib/sqlalchemy/orm/relationships.py
index 7882eff70..2224b4902 100644
--- a/lib/sqlalchemy/orm/relationships.py
+++ b/lib/sqlalchemy/orm/relationships.py
@@ -3427,6 +3427,14 @@ class JoinCondition(object):
                         and pr not in self.prop._reverse_property
                         and pr.key not in self.prop._overlaps
                         and self.prop.key not in pr._overlaps
+                        # note: the "__*" symbol is used internally by
+                        # SQLAlchemy as a general means of supressing the
+                        # overlaps warning for some extension cases, however
+                        # this is not currently
+                        # a publicly supported symbol and may change at
+                        # any time.
+                        and "__*" not in self.prop._overlaps
+                        and "__*" 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)
-- 
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