1 files changed, 35 insertions, 8 deletions
diff --git a/alembic/util/langhelpers.py b/alembic/util/langhelpers.py
index 1fb0942..6c92e3c 100644
--- a/alembic/util/langhelpers.py
+++ b/alembic/util/langhelpers.py
@@ -257,30 +257,57 @@ class immutabledict(dict):
 
 
 class Dispatcher(object):
-    def __init__(self):
+    def __init__(self, uselist=False):
         self._registry = {}
+        self.uselist = uselist
 
     def dispatch_for(self, target, qualifier='default'):
         def decorate(fn):
-            assert isinstance(target, type)
-            assert target not in self._registry
-            self._registry[(target, qualifier)] = fn
+            if self.uselist:
+                assert target not in self._registry
+                self._registry.setdefault((target, qualifier), []).append(fn)
+            else:
+                assert target not in self._registry
+                self._registry[(target, qualifier)] = fn
             return fn
         return decorate
 
     def dispatch(self, obj, qualifier='default'):
-        for spcls in type(obj).__mro__:
+
+        if isinstance(obj, string_types):
+            targets = [obj]
+        elif isinstance(obj, type):
+            targets = obj.__mro__
+        else:
+            targets = type(obj).__mro__
+
+        for spcls in targets:
             if qualifier != 'default' and (spcls, qualifier) in self._registry:
-                return self._registry[(spcls, qualifier)]
+                return self._fn_or_list(self._registry[(spcls, qualifier)])
             elif (spcls, 'default') in self._registry:
-                return self._registry[(spcls, 'default')]
+                return self._fn_or_list(self._registry[(spcls, 'default')])
         else:
             raise ValueError("no dispatch function for object: %s" % obj)
 
+    def _fn_or_list(self, fn_or_list):
+        if self.uselist:
+            def go(*arg, **kw):
+                for fn in fn_or_list:
+                    fn(*arg, **kw)
+            return go
+        else:
+            return fn_or_list
+
     def branch(self):
         """Return a copy of this dispatcher that is independently
         writable."""
 
         d = Dispatcher()
-        d._registry.update(self._registry)
+        if self.uselist:
+            d._registry.update(
+                (k, [fn for fn in self._registry[k]])
+                for k in self._registry
+            )
+        else:
+            d._registry.update(self._registry)
         return d