Allow SchemaType and Variant to work together

Added support for the :class:`.Variant` and the :class:`.SchemaType`
objects to be compatible with each other.  That is, a variant
can be created against a type like :class:`.Enum`, and the instructions
to create constraints and/or database-specific type objects will
propagate correctly as per the variant's dialect mapping.

Also added testing for some potential double-event scenarios
on TypeDecorator but it seems usually this doesn't occur.

Change-Id: I4a7e7c26b4133cd14e870f5bc34a1b2f0f19a14a
Fixes: #2892

1 files changed, 40 insertions, 5 deletions

diff --git a/test/sql/test_metadata.py b/test/sql/test_metadata.py
index bd67b6f69..6d0df3b5f 100644
--- a/test/sql/test_metadata.py
+++ b/test/sql/test_metadata.py
@@ -1607,7 +1607,7 @@ class SchemaTypeTest(fixtures.TestBase):
             impl = target_typ
 
         typ = MyType()
-        self._test_before_parent_attach(typ, target_typ)
+        self._test_before_parent_attach(typ, target_typ, double=True)
 
     def test_before_parent_attach_typedec_of_schematype(self):
         class MyType(TypeDecorator, sqltypes.SchemaType):
@@ -1623,17 +1623,52 @@ class SchemaTypeTest(fixtures.TestBase):
         typ = MyType()
         self._test_before_parent_attach(typ)
 
-    def _test_before_parent_attach(self, typ, evt_target=None):
+    def _test_before_parent_attach(self, typ, evt_target=None, double=False):
         canary = mock.Mock()
 
         if evt_target is None:
             evt_target = typ
 
-        event.listen(evt_target, "before_parent_attach", canary.go)
+        orig_set_parent = evt_target._set_parent
+        orig_set_parent_w_dispatch = evt_target._set_parent_with_dispatch
 
-        c = Column('q', typ)
+        def _set_parent(parent):
+            orig_set_parent(parent)
+            canary._set_parent(parent)
 
-        eq_(canary.mock_calls, [mock.call.go(evt_target, c)])
+        def _set_parent_w_dispatch(parent):
+            orig_set_parent_w_dispatch(parent)
+            canary._set_parent_with_dispatch(parent)
+
+        with mock.patch.object(evt_target, '_set_parent', _set_parent):
+            with mock.patch.object(
+                    evt_target, '_set_parent_with_dispatch',
+                    _set_parent_w_dispatch):
+                event.listen(evt_target, "before_parent_attach", canary.go)
+
+                c = Column('q', typ)
+
+        if double:
+            # no clean way yet to fix this, inner schema type is called
+            # twice, but this is a very unusual use case.
+            eq_(
+                canary.mock_calls,
+                [
+                    mock.call._set_parent(c),
+                    mock.call.go(evt_target, c),
+                    mock.call._set_parent(c),
+                    mock.call._set_parent_with_dispatch(c)
+                ]
+            )
+        else:
+            eq_(
+                canary.mock_calls,
+                [
+                    mock.call.go(evt_target, c),
+                    mock.call._set_parent(c),
+                    mock.call._set_parent_with_dispatch(c)
+                ]
+            )
 
     def test_independent_schema(self):
         m = MetaData()