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, 7 insertions, 3 deletions

diff --git a/lib/sqlalchemy/util/langhelpers.py b/lib/sqlalchemy/util/langhelpers.py
index 973de426c..68c0f885b 100644
--- a/lib/sqlalchemy/util/langhelpers.py
+++ b/lib/sqlalchemy/util/langhelpers.py
@@ -529,20 +529,24 @@ class portable_instancemethod(object):
 
     """
 
-    __slots__ = 'target', 'name', '__weakref__'
+    __slots__ = 'target', 'name', 'kwargs', '__weakref__'
 
     def __getstate__(self):
-        return {'target': self.target, 'name': self.name}
+        return {'target': self.target, 'name': self.name,
+                'kwargs': self.kwargs}
 
     def __setstate__(self, state):
         self.target = state['target']
         self.name = state['name']
+        self.kwargs = state.get('kwargs', ())
 
-    def __init__(self, meth):
+    def __init__(self, meth, kwargs=()):
         self.target = meth.__self__
         self.name = meth.__name__
+        self.kwargs = kwargs
 
     def __call__(self, *arg, **kw):
+        kw.update(self.kwargs)
         return getattr(self.target, self.name)(*arg, **kw)