dirnode.set_children: change return value: fire with self instead of None

src/allmydata/dirnode.py

@@ -415,7 +415,9 @@ class DirectoryNode:
                 msg = "cannot pack unknown node as child %s" % str(name)
                 raise CannotPackUnknownNodeError(msg)
             a.set_node(name, child_node, metadata)
-        return self._node.modify(a.modify)
+        d = self._node.modify(a.modify)
+        d.addCallback(lambda ign: self)
+        return d
 
     def set_node(self, name, child, metadata=None, overwrite=True):
         """I add a child at the specific name. I return a Deferred that fires

src/allmydata/interfaces.py

@@ -901,9 +901,9 @@ class IDirectoryNode(IMutableFilesystemNode):
         """Add multiple children (by writecap+readcap) to a directory node.
         Takes a dictionary, with childname as keys and (writecap, readcap)
         tuples (or (writecap, readcap, metadata) triples) as values. Returns
-        a Deferred that fires (with None) when the operation finishes. This
-        is equivalent to calling set_uri() multiple times, but is much more
-        efficient. All child names must be unicode strings.
+        a Deferred that fires (with this dirnode) when the operation
+        finishes. This is equivalent to calling set_uri() multiple times, but
+        is much more efficient. All child names must be unicode strings.
         """
 
     def set_node(name, child, metadata=None, overwrite=True):

src/allmydata/test/test_dirnode.py

@@ -455,6 +455,7 @@ class Dirnode(GridTestMixin, unittest.TestCase,
                               u"e3": (fake_file_uri, fake_file_uri,
                                       {"key": "value"}),
                               }))
+            d.addCallback(lambda n2: self.failUnlessIdentical(n2, n))
             d.addCallback(lambda res:
                           self.shouldFail(ExistingChildError, "set_children-no",
                                           "child 'e1' already exists",