detech empty pathname components, hopefully the same way as Nevow

src/allmydata/test/web/test_web.py

@@ -1737,7 +1737,7 @@ class Web(WebMixin, WebErrorMixin, testutil.StallMixin, testutil.ReallyEqualMixi
         return d
 
     # XXX this 'fails' (as it should), but not with '409 Conflict' ... 
-    def _test_PUT_NEWFILEURL_blocked(self):
+    def test_PUT_NEWFILEURL_blocked(self):
         d = self.PUT(self.public_url + "/foo/blockingfile/new.txt",
                      self.NEWFILE_CONTENTS)
         d.addBoth(self.shouldFail, error.Error, "PUT_NEWFILEURL_blocked",

src/allmydata/web/directory.py

@@ -112,6 +112,14 @@ class DirectoryNodeHandler(ReplaceMeMixin, Resource, object):
         # or no further children) renders "this" page
         name = name.decode('utf8')
         if not name:
+            # replicating Nevow behavior that complains about "empty
+            # path segments" .. but twisted.web sends in "name=None"
+            # for a URL like "/foo/bar/" as well as "/foo//bar"
+            # (i.e. a trailing slash means "name=None" as well)
+            if b'//' in req.path:
+                raise EmptyPathnameComponentError(
+                    u"The webapi does not allow empty pathname components, i.e. a double slash",
+                )
             return self
         d = self.node.get(name)
         d.addBoth(self._got_child, req, name)