[Twisted-Python] Patch for flavors.py?

[Jasper Phillips]

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I was talking with Kevin Turner at the pub last night after the "Porpig"
meeting, and he mentioned having the same problem with circular references I
was having, so I offered to post the klu... err, patch I had for the problem.


In short, it checks for _Dereference's (corresponding to dictionaries not yet
available) that are destined to be (erroneously) copied into the __dict__ of
an object that is then returned.  When one is found, it is returned instead
without a containing object, and a method object is scheduled to be run
via postUnjelly.

Later on (in crefutil.py), after the _Derefence has been magically replaced
by it's corresponding dictionary, the dictionary is taken and stored in
the __dict__ of a newly created object.  Even later, the postUnjelly
scheduled earlier is called, which sets the __class__ of the manually
created object.


This is a pretty hideous fix!  But it is minimal, and I think unlikely to
have side effects.  Then again, I do not have a broad understanding of
twisted, and haven't tested it extensively...  Clearly what newjelly.py is
aiming for is superior, and so I haven't been inclined to invest any further
effort.

The cvs -u for the two files affected follows.  Use them as you wish, and
critique is always welcome.

- -Jasper



Index: flavors.py
===================================================================
RCS file: /cvs/Twisted/twisted/spread/flavors.py,v
retrieving revision 1.28
diff -u -r1.28 flavors.py
- --- flavors.py  17 Feb 2003 20:48:30 -0000      1.28
+++ flavors.py  8 Apr 2003 18:16:27 -0000
@@ -388,9 +388,26 @@
     def unjellyFor(self, unjellier, jellyList):
         if unjellier.invoker is None:
             return setInstanceState(self, unjellier, jellyList)
- -        self.setCopyableState(unjellier.unjelly(jellyList[1]))
- -        return self
+        state = unjellier.unjelly( jellyList[1] )
 
+        from twisted.persisted.crefutil import _Dereference
+        if isinstance( state, _Dereference ):
+            # In the caller (jelly._Unjellier.unjelly()),
+            # presence of state.postUnjelly triggers a call to self.postUnjelly
+            # This seems like a bug...
+            state.postUnjelly = 1
+            self.postUnjelly  = ClassReset( state, self.__class__ )
+            return state
+        else:
+            self.setCopyableState( state )
+            return self
+        
+class ClassReset( object ):
+    def __init__( self, obj, klass ):
+        self.obj   = obj
+        self.klass = klass
+    def __call__( self ):
+        self.obj.__class__ = self.klass
 
 
 class RemoteCache(RemoteCopy, Serializable):

Index: crefutil.py
===================================================================
RCS file: /cvs/Twisted/twisted/persisted/crefutil.py,v
retrieving revision 1.11
diff -u -r1.11 crefutil.py
- --- crefutil.py 31 Mar 2003 00:28:34 -0000      1.11
+++ crefutil.py 8 Apr 2003 19:18:06 -0000
@@ -114,6 +114,17 @@
         NotKnown.__init__(self)
         self.id = id
 
+    def resolveDependants(self, newObject):
+        self.resolved = 1
+        self.resolvedObject = newObject
+        for mut, key in self.dependants:
+            inst           = mut.value
+            inst.__dict__  = newObject
+            mut[key]       = inst
+
+            if isinstance(newObject, NotKnown):
+                newObject.addDependant(mut, key)
+
 
 from twisted.internet.defer import Deferred

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