.

wcfs/internal/xbtree.py

@@ -89,7 +89,7 @@ better:
 from __future__ import print_function, absolute_import
 
 from BTrees import check as zbcheck
-from golang import func, panic
+from golang import func, panic, defer
 from golang.gcompat import qq
 import itertools
 import re
@@ -216,12 +216,30 @@ def StructureOf(znode):
 # topology structure.
 #
 # NOTE ZODB BTree package does not tolerate structures with empty BTree nodes
-# except for the single case of empty tree.
+# except for the sole single case of empty tree.
+@func
 def Restructure(ztree, newStructure):
     _ = _zclassify(ztree)
     assert _.is_ztree
     assert isinstance(newStructure, Tree)
-    #print('\nRestructure %s ->\n%s' % (ztree, newStructure))
+
+    from_ = TopoEncode(StructureOf(ztree))
+    to_   = TopoEncode(newStructure)
+    """
+    def _():
+        exc = recover() # FIXME for panic - returns unwrapped arg, not PanicError
+        if exc is not None:
+            # FIXME %w creates only .Unwrap link, not with .__cause__ -> fix
+            raise fmt.Errorf("Restructure %s -> %s: %w", from_, to_, exc)
+    defer(_)
+    """
+    def _(): # XXX hack
+        exc = sys.exc_info()[1]
+        if exc is not None:
+            assert len(exc.args) == 1
+            exc.args = ("Restructure %s -> %s: %r" % (from_, to_, exc.args[0]),)
+    defer(_)
+
 
     ztreeType   = type(ztree)
     zbucketType = ztreeType._bucket_type
@@ -244,7 +262,7 @@ def Restructure(ztree, newStructure):
     # - find solution to linear assignment problem A <- B with the cost given by D
     #   https://en.wikipedia.org/wiki/Assignment_problem
     #
-    # D(A,B) = |A.lo, B.lo| + |A.hi - B.hi|
+    # D(A,B) = |A.lo - B.lo| + |A.hi - B.hi|
 
     # we will modify nodes from new set:
     # - node.Z              will point to associated znode
@@ -312,8 +330,7 @@ def Restructure(ztree, newStructure):
             # assert the result is 1-1 mapping
             for j in range(len(RNv)):
                 if RNv[j].node.Z is not RZv[j].node:
-                    panic("BUG: Restructure %s -> %s: assign: not 1-1 mapping:\n RZv: %s\nRNv: %s" %
-                            (TopoEncode(StructureOf(ztree)), TopoEncode(newStructure), RZv, RNv))
+                    panic("BUG: assign: not 1-1 mapping:\n RZv: %s\nRNv: %s" % (RZv, RNv))
 
         # XXX assert assignments are in key↑ order ?