.

wcfs/internal/xbtree.py

@@ -249,7 +249,8 @@ def StructureOf(znode, onlyKeys=False):
 # Restructure reorganizes ZODB BTree instance (not Tree) according to specified
 # topology structure.
 #
-# The new structure should be given with key-only buckets.
+# The new structure should be usually given with key-only buckets.
+# If new structure comes with values, values associated with keys must not be changed.
 #
 # NOTE ZODB BTree package does not tolerate structures with empty BTree nodes
 # except for the sole single case of empty tree.
@@ -498,7 +499,7 @@ def Restructure(ztree, newStructure):
                     assert len(node.keyv) == len(node.valuev)
                     for (k,v) in zip(node.keyv, node.valuev):
                         if kv[k] is not v:
-                            raise ValueError("target bucket changes [%d] %r -> %r", k, kv[k], v)
+                            raise ValueError("target bucket changes [%d] %r -> %r" % (k, kv[k], v))
 
                 zstate = ()
                 for k in node.keyv:

wcfs/internal/xbtree_test.py

@@ -687,7 +687,9 @@ def test_restructure():
     assert b0[0] is X[0]
     assert b2[2] is X[2]
 
-    # XXX raises if k->v different
+    # [2] changes value from X[2] to X[3]
+    with raises(ValueError, match=r"target bucket changes \[2\]"):
+        R(z, T([1], Bv([0],X[0]), Bv([2],X[3])))
 
 
     # ---- tricky cases