Allow update.returing() to work with from_statement()

The ORM used in :term:`2.0 style` can now return ORM objects from the rows
returned by an UPDATE..RETURNING or INSERT..RETURNING statement, by
supplying the construct to :meth:`_sql.Select.from_statement` in an ORM
context.

Change-Id: I59c9754ff1cb3184580dd5194ecd2971d4e7f8e8
References: #5940

1 files changed, 7 insertions, 1 deletions

diff --git a/lib/sqlalchemy/sql/dml.py b/lib/sqlalchemy/sql/dml.py
index 3f492a490..ea10bfc27 100644
--- a/lib/sqlalchemy/sql/dml.py
+++ b/lib/sqlalchemy/sql/dml.py
@@ -47,6 +47,10 @@ class DMLState(CompileState):
     def __init__(self, statement, compiler, **kw):
         raise NotImplementedError()
 
+    @property
+    def dml_table(self):
+        return self.statement.table
+
     def _make_extra_froms(self, statement):
         froms = []
 
@@ -407,7 +411,9 @@ class UpdateBase(
             raise exc.InvalidRequestError(
                 "return_defaults() is already configured on this statement"
             )
-        self._returning += cols
+        self._returning += tuple(
+            coercions.expect(roles.ColumnsClauseRole, c) for c in cols
+        )
 
     def _exported_columns_iterator(self):
         """Return the RETURNING columns as a sequence for this statement.