Add Dependency.hierarchy() to better visualize the origin of a dependency.

gclient.py

 #!/usr/bin/python
 # Copyright (c) 2010 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Meta checkout manager supporting both Subversion and GIT.
 
 Files
   .gclient      : Current client configuration, written by 'config' command.
                   Format is a Python script defining 'solutions', a list whose
@@ skipping 142 matching lines @@
     self.deps_file = deps_file or self.DEPS_FILE
     # A cache of the files affected by the current operation, necessary for
     # hooks.
     self.file_list = []
     self.deps_parsed = False
     self.direct_reference = False
 
     # Sanity checks
     if not self.name and self.parent:
       raise gclient_utils.Error('Dependency without name')
-    if self.name in [d.name for d in self.tree(False)]:
-      raise gclient_utils.Error('Dependency %s specified more than once' %
-          self.name)
+    tree = dict((d.name, d) for d in self.tree(False))
+    if self.name in tree:
+      raise gclient_utils.Error(
+          'Dependency %s specified more than once:\n  %s\nvs\n  %s' %
+          (self.name, tree[self.name].hierarchy(), self.hierarchy()))
     if not isinstance(self.url,
         (basestring, self.FromImpl, self.FileImpl, None.__class__)):
       raise gclient_utils.Error('dependency url must be either a string, None, '
                                 'File() or From() instead of %s' %
                                 self.url.__class__.__name__)
     if '/' in self.deps_file or '\\' in self.deps_file:
       raise gclient_utils.Error('deps_file name must not be a path, just a '
                                 'filename. %s' % self.deps_file)
 
   def LateOverride(self, url):
@@ skipping 253 matching lines @@
         out.append('%s: %s' % (i, self.__dict__[i]))
 
     for d in self.dependencies:
       out.extend(['  ' + x for x in str(d).splitlines()])
       out.append('')
     return '\n'.join(out)
 
   def __repr__(self):
     return '%s: %s' % (self.name, self.url)
 
+  def hierarchy(self):
+    "Returns a human-readable hierarchical reference to a Dependency."

[bradn, 2010/07/22 21:22:25]

Uh you'll want a """ here I believe.

+    out = '%s(%s)' % (self.name, self.url)
+    i = self.parent
+    while i and i.name:
+      out = '%s(%s) -> %s' % (i.name, i.url, out)
+      i = i.parent
+    return out
+
 
 class GClient(Dependency):
   """Object that represent a gclient checkout. A tree of Dependency(), one per
   solution or DEPS entry."""
 
   DEPS_OS_CHOICES = {
     "win32": "win",
     "win": "win",
     "cygwin": "win",
     "darwin": "mac",
@@ skipping 683 matching lines @@
     return CMDhelp(parser, argv)
   except gclient_utils.Error, e:
     print >> sys.stderr, 'Error: %s' % str(e)
     return 1
 
 
 if '__main__' == __name__:
   sys.exit(Main(sys.argv[1:]))
 
 # vim: ts=2:sw=2:tw=80:et: