We weren't computing the virtual root correctly in a corner case.

1 files changed, 31 insertions, 32 deletions

diff --git a/repoze/bfg/traversal.py b/repoze/bfg/traversal.py
index 59ad9115d..2b9a0e611 100644
--- a/repoze/bfg/traversal.py
+++ b/repoze/bfg/traversal.py
@@ -502,69 +502,68 @@ class ModelGraphTraverser(object):
             # this request did not match a Routes route
             subpath = ()
             try:
-                path = environ['PATH_INFO']
+                path = environ['PATH_INFO'] or '/'
             except KeyError:
                 path = '/'
 
         try:
-            vroot_path_string = environ[VH_ROOT_KEY]
+            vroot_path = environ[VH_ROOT_KEY]
         except KeyError:
-            vroot_path = ()
-            vroot_idx = 0
+            vroot_tuple = ()
+            vpath = path
+            vroot_idx = -1
         else:
-            vroot_path = traversal_path(vroot_path_string)
-            vroot_idx = len(vroot_path)
-            path = vroot_path_string + path
+            vroot_tuple = traversal_path(vroot_path)
+            vpath = vroot_path + path
+            vroot_idx = len(vroot_tuple) -1
 
         ob = vroot = self.root
 
-        if (not path) or path == '/':
-            # save a call to traversal_path if we know it's going to return
-            # the empty tuple
-            path = ()
+        if vpath == '/' or (not vpath):
+            # prevent a call to traversal_path if we know it's going
+            # to return the empty tuple
+            vpath_tuple = ()
         else:
-            path = traversal_path(path)
-
-            # in case you're wondering, we do dead reckoning here instead
-            # of pushing and popping temporary lists for speed purposes
-
-            i = 1
-            j = vroot_idx
-
-            for segment in path:
+            # we do dead reckoning here via tuple slicing instead of
+            # pushing and popping temporary lists for speed purposes
+            # and this hurts readability; apologies
+            i = 0
+            vpath_tuple = traversal_path(vpath)
+            for segment in vpath_tuple:
                 if segment[:2] =='@@':
                     return dict(context=ob, view_name=segment[2:],
-                                subpath=path[i:], traversed=path[:j],
+                                subpath=vpath_tuple[i+1:],
+                                traversed=vpath_tuple[:vroot_idx+i+1],
                                 virtual_root=vroot,
-                                virtual_root_path=vroot_path,
+                                virtual_root_path=vroot_tuple,
                                 root=self.root)
                 try:
                     getitem = ob.__getitem__
                 except AttributeError:
                     return dict(context=ob, view_name=segment,
-                                subpath=path[i:], traversed=path[:j],
+                                subpath=vpath_tuple[i+1:],
+                                traversed=vpath_tuple[:vroot_idx+i+1],
                                 virtual_root=vroot,
-                                virtual_root_path=vroot_path,
+                                virtual_root_path=vroot_tuple,
                                 root=self.root)
 
                 try:
                     next = getitem(segment)
                 except KeyError:
                     return dict(context=ob, view_name=segment,
-                                subpath=path[i:], traversed=path[:j],
+                                subpath=vpath_tuple[i+1:],
+                                traversed=vpath_tuple[:vroot_idx+i+1],
                                 virtual_root=vroot,
-                                virtual_root_path=vroot_path,
+                                virtual_root_path=vroot_tuple,
                                 root=self.root)
-
-                if vroot_idx == i-1:
-                    vroot = ob
+                if i == vroot_idx: 
+                    vroot = next
                 ob = next
                 i += 1
-                j += 1
 
         return dict(context=ob, view_name=u'', subpath=subpath,
-                    traversed=path, virtual_root=vroot,
-                    virtual_root_path=vroot_path, root=self.root)
+                    traversed=vpath_tuple, virtual_root=vroot,
+                    virtual_root_path=vroot_tuple, root=self.root)
 
 class TraversalContextURL(object):
     """ The IContextURL adapter used to generate URLs for a context