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

1 files changed, 8 insertions, 0 deletions

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)