ensure SelectState.all_selected_columns not memoized as a generator

This regression was found from #6261 before release of 1.4.12

Fixes: #6261
Fixes: #6394
Change-Id: I4c2c5da02dbcf5c2cea26c81d3521de892ef428e

1 files changed, 11 insertions, 0 deletions

diff --git a/test/sql/test_selectable.py b/test/sql/test_selectable.py
index 2403db7c9..b54ef02fd 100644
--- a/test/sql/test_selectable.py
+++ b/test/sql/test_selectable.py
@@ -590,6 +590,17 @@ class SelectableTest(
             "table1.col3, table1.colx FROM table1) AS anon_1",
         )
 
+    def test_scalar_subquery_from_subq_same_source(self):
+        s1 = select(table1.c.col1)
+
+        for i in range(2):
+            stmt = s1.subquery().select().scalar_subquery()
+            self.assert_compile(
+                stmt,
+                "(SELECT anon_1.col1 FROM "
+                "(SELECT table1.col1 AS col1 FROM table1) AS anon_1)",
+            )
+
     def test_type_coerce_preserve_subq(self):
         class MyType(TypeDecorator):
             impl = Integer