remove should_nest behavior for contains_eager()

Fixed regression for 1.4 in :func:`_orm.contains_eager` where the "wrap in
subquery" logic of :func:`_orm.joinedload` would be inadvertently triggered
for use of the :func:`_orm.contains_eager` function with similar statements
(e.g. those that use ``distinct()``, ``limit()`` or ``offset()``). This is
not appropriate for :func:`_orm.contains_eager` which has always had the
contract that the user-defined SQL statement is unmodified with the
exception of adding the appropriate columns.

Also includes an adjustment to the assertion in Label._make_proxy()
which was there to prevent a fixed label name from being anonymized;
if the label is already anonymous, the change should proceed.
This logic was being hit before the contains_eager behavior was
adjusted. With the adjustment, this code is not used.

Fixes: #8569
Change-Id: I161e65041c0162fd2b83cbef40f57a50fcfaf0fd

1 files changed, 21 insertions, 1 deletions

diff --git a/test/sql/test_selectable.py b/test/sql/test_selectable.py
index 3ecbfca27..64ff2e421 100644
--- a/test/sql/test_selectable.py
+++ b/test/sql/test_selectable.py
@@ -404,8 +404,10 @@ class SelectableTest(
 
     @testing.combinations((True,), (False,))
     def test_broken_select_same_named_explicit_cols(self, use_anon):
-        # this is issue #6090.  the query is "wrong" and we dont know how
+        """test for #6090. the query is "wrong" and we dont know how
         # to render this right now.
+
+        """
         stmt = select(
             table1.c.col1,
             table1.c.col2,
@@ -432,6 +434,24 @@ class SelectableTest(
             ):
                 select(stmt.subquery()).compile()
 
+    def test_same_anon_named_explicit_cols(self):
+        """test for #8569.  This adjusts the change in #6090 to not apply
+        to anonymous labels.
+
+        """
+        lc = literal_column("col2").label(None)
+
+        subq1 = select(lc).subquery()
+
+        stmt2 = select(subq1, lc).subquery()
+
+        self.assert_compile(
+            select(stmt2),
+            "SELECT anon_1.col2_1, anon_1.col2_1_1 FROM "
+            "(SELECT anon_2.col2_1 AS col2_1, col2 AS col2_1 FROM "
+            "(SELECT col2 AS col2_1) AS anon_2) AS anon_1",
+        )
+
     def test_correlate_none_arg_error(self):
         stmt = select(table1)
         with expect_raises_message(