Beginning work on GN build

tools/gypi_to_gn.py

 # Copyright 2014 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.
 
 """Converts a given gypi file to a python scope and writes the result to stdout.
 
 It is assumed that the file contains a toplevel dictionary, and this script
 will return that dictionary as a GN "scope" (see example below). This script
 does not know anything about GYP and it will not expand variables or execute
 conditions.
@@ skipping 110 matching lines @@
     result = {}
     for key, value in values.items():
       new_key = ReplaceSubstrings(key, search_for, replace_with)
       new_value = ReplaceSubstrings(value, search_for, replace_with)
       result[new_key] = new_value
     return result
 
   # Assume everything else is unchanged.
   return values
 
+def KeepOnly(values, filters):
+  """Recursively filters out strings not ending in "f" from "values"""
+
+  if isinstance(values, list):
+    return [v for v in values if v.endswith(tuple(filters))]
+
+  if isinstance(values, dict):
+    result = {}
+    for key, value in values.items():
+      new_key = KeepOnly(key, filters)
+      new_value = KeepOnly(value, filters)
+      result[new_key] = new_value
+    return result
+
+  return values
+
 def main():
   parser = OptionParser()
   parser.add_option("-r", "--replace", action="append",
     help="Replaces substrings. If passed a=b, replaces all substrs a with b.")
+  parser.add_option("-k", "--keep_only", default = [], action="append",
+    help="Keeps only files ending with the listed strings.")
   (options, args) = parser.parse_args()
 
   if len(args) != 1:
     raise Exception("Need one argument which is the .gypi file to read.")
 
   data = LoadPythonDictionary(args[0])
   if options.replace:
     # Do replacements for all specified patterns.
     for replace in options.replace:
       split = replace.split('=')
       # Allow "foo=" to replace with nothing.
       if len(split) == 1:
         split.append('')
       assert len(split) == 2, "Replacement must be of the form 'key=value'."
       data = ReplaceSubstrings(data, split[0], split[1])
 
+  if options.keep_only != []:
+    data = KeepOnly(data, options.keep_only)
+
   # Sometimes .gypi files use the GYP syntax with percents at the end of the
   # variable name (to indicate not to overwrite a previously-defined value):
   #   'foo%': 'bar',
   # Convert these to regular variables.
   for key in data:
     if len(key) > 1 and key[len(key) - 1] == '%':
       data[key[:-1]] = data[key]
       del data[key]
 
   print gn_helpers.ToGNString(data)
 
 if __name__ == '__main__':
   try:
     main()
   except Exception, e:
     print str(e)
     sys.exit(1)