Make a common approach for "emulated" types

Internal refinements to the :class:`.Enum`, :class:`.Interval`, and
:class:`.Boolean` types, which now extend a common mixin
:class:`.Emulated` that indicates a type that provides Python-side
emulation of a DB native type, switching out to the DB native type when a
supporting backend is in use.   The Postgresql :class:`.INTERVAL` type
when used directly will now include the correct type coercion rules for
SQL expressions that also take effect for :class:`.sqltypes.Interval`
(such as adding a date to an interval yields a datetime).

Change-Id: Ifb9f9d7cbd9f5990dcb2abb583193e9e92b789ad
Fixes: #4088

1 files changed, 18 insertions, 0 deletions

diff --git a/test/sql/test_metadata.py b/test/sql/test_metadata.py
index e204375f4..35e0c9c1d 100644
--- a/test/sql/test_metadata.py
+++ b/test/sql/test_metadata.py
@@ -1797,6 +1797,24 @@ class SchemaTypeTest(fixtures.TestBase):
 
         is_true(y_copy.type._create_events)
 
+        # for Postgresql, this will emit CREATE TYPE
+        m.dispatch.before_create(t1, testing.db)
+        try:
+            eq_(t1.c.y.type.evt_targets, (t1, ))
+        finally:
+            # do the drop so that Postgresql emits DROP TYPE
+            m.dispatch.after_drop(t1, testing.db)
+
+    def test_enum_nonnative_column_copy_transfers_events(self):
+        m = MetaData()
+
+        type_ = self.WrapEnum('a', 'b', 'c', name='foo', native_enum=False)
+        y = Column('y', type_)
+        y_copy = y.copy()
+        t1 = Table('x', m, y_copy)
+
+        is_true(y_copy.type._create_events)
+
         m.dispatch.before_create(t1, testing.db)
         eq_(t1.c.y.type.evt_targets, (t1, ))