Fixed a gotcha where inadvertently calling list() on a

      :class:`.ColumnElement` would go into an endless loop, if
      :meth:`.ColumnOperators.__getitem__` were implemented.
      A new NotImplementedError is emitted via ``__iter__()``.

1 files changed, 12 insertions, 0 deletions

diff --git a/test/sql/test_operators.py b/test/sql/test_operators.py
index eb2885658..9da9d94c3 100644
--- a/test/sql/test_operators.py
+++ b/test/sql/test_operators.py
@@ -325,6 +325,18 @@ class ExtensionOperatorTest(fixtures.TestBase, testing.AssertsCompiledSQL):
             "x -> :x_1"
         )
 
+    def test_no_endless_list_call(self):
+        class MyType(UserDefinedType):
+            class comparator_factory(UserDefinedType.Comparator):
+                def __getitem__(self, index):
+                    return self.op("->")(index)
+
+        assert_raises_message(
+            NotImplementedError,
+            "Class <class 'sqlalchemy.schema.Column'> is not iterable",
+            list, Column('x', MyType())
+        )
+
     def test_lshift(self):
         class MyType(UserDefinedType):
             class comparator_factory(UserDefinedType.Comparator):