Only return a Deferred from DBObject.__new__ if afterInit actually re…

…turns a Deferredl; refs bmuller#34

This does not ensure backwards compabitility--previously since
afterInit was not called during instantiation, instantiation was never
deferred--but sure does improve it by providing it in cases where
afterInit is not deferred.

twistar/dbobject.py

@@ -61,11 +61,15 @@ class DBObject(Validator):
     def __new__(cls, *args, **kwargs):
         try:
             ret = super(DBObject, cls).__new__(cls, *args, **kwargs)
-            ret.__init__(*args, **kwargs)
         except:
             return defer.fail()
         else:
-            return defer.maybeDeferred(ret.afterInit).addCallback(lambda _: ret)
+            d = ret.afterInit()
+            if isinstance(d, defer.Deferred):
+                ret.__init__(*args, **kwargs)
+                return d.addCallback(lambda _: ret)
+            else:
+                return ret
 
 
     def __init__(self, **kwargs):
@@ -387,7 +391,7 @@ def findOrCreate(klass, **attrs):
         def _findOrCreate(trans):
             def handle(result):
                 if len(result) == 0:
-                    return klass(**attrs).addCallback(lambda inst: inst.save())
+                    return defer.maybeDeferred(klass, **attrs).addCallback(lambda inst: inst.save())
                 return result[0]
             return klass.findBy(**attrs).addCallback(handle)
         return _findOrCreate()

twistar/utils.py

@@ -45,7 +45,7 @@ def createInstances(props, klass):
     """
     if type(props) is list:
         return defer.DeferredList(
-            [klass(**prop) for prop in props], fireOnOneErrback=True, consumeErrors=True
+            [defer.maybeDeferred(klass, **prop) for prop in props], fireOnOneErrback=True, consumeErrors=True
         ).addCallback(lambda result: [x[1] for x in result])
     elif props is not None:
         return klass(**props)