propagate proxy_key from WrapsColumnExpression

this allows cast() of a label() to propagate the
proxy key outwards in the same way that it apparently
works at the SQL level.

This is stuffing even more rules into naming so basically
seeing how far we can go without other cases starting
to fail.

Fixes: #8084
Change-Id: I20bd97dae798fee6492334c06934e807d0f269ef

2 files changed, 30 insertions, 1 deletions

diff --git a/test/sql/test_compiler.py b/test/sql/test_compiler.py
index 6ad2aa2c1..94c38548f 100644
--- a/test/sql/test_compiler.py
+++ b/test/sql/test_compiler.py
@@ -3298,7 +3298,7 @@ class SelectTest(fixtures.TestBase, AssertsCompiledSQL):
             (exprs[1], "hoho", "hoho(mytable.myid)", "hoho_1"),
             (
                 exprs[2],
-                "_no_label",
+                "name",
                 "CAST(mytable.name AS NUMERIC)",
                 "name",  # due to [ticket:4449]
             ),
@@ -3322,6 +3322,7 @@ class SelectTest(fixtures.TestBase, AssertsCompiledSQL):
                 t = table1
 
             s1 = select(col).select_from(t)
+            eq_(col._proxy_key, key if key != "_no_label" else None)
             eq_(list(s1.subquery().c.keys()), [key])
 
             if lbl:
diff --git a/test/sql/test_labels.py b/test/sql/test_labels.py
index 8c8e9dbed..d385b9e8d 100644
--- a/test/sql/test_labels.py
+++ b/test/sql/test_labels.py
@@ -26,6 +26,7 @@ from sqlalchemy.testing import AssertsCompiledSQL
 from sqlalchemy.testing import engines
 from sqlalchemy.testing import eq_
 from sqlalchemy.testing import fixtures
+from sqlalchemy.testing import is_
 from sqlalchemy.testing import mock
 from sqlalchemy.testing.schema import Column
 from sqlalchemy.testing.schema import Table
@@ -938,6 +939,33 @@ class ColExprLabelTest(fixtures.TestBase, AssertsCompiledSQL):
             "some_table.name FROM some_table",
         )
 
+    @testing.combinations("inside", "outside")
+    def test_wraps_col_expr_label_propagate(self, cast_location):
+        """test #8084"""
+
+        table1 = self.table1
+
+        if cast_location == "inside":
+            expr = cast(table1.c.name, Integer).label("foo")
+        elif cast_location == "outside":
+            expr = cast(table1.c.name.label("foo"), Integer)
+        else:
+            assert False
+
+        self.assert_compile(
+            select(expr),
+            "SELECT CAST(some_table.name AS INTEGER) AS foo FROM some_table",
+        )
+        is_(select(expr).selected_columns.foo, expr)
+
+        subq = select(expr).subquery()
+        self.assert_compile(
+            select(subq).where(subq.c.foo == 10),
+            "SELECT anon_1.foo FROM (SELECT CAST(some_table.name AS INTEGER) "
+            "AS foo FROM some_table) AS anon_1 WHERE anon_1.foo = :foo_1",
+            checkparams={"foo_1": 10},
+        )
+
     def test_type_coerce_auto_label_label_style_disambiguate(self):
         table1 = self.table1