build/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 (it will check for the presence of a "conditions" value in the
dictionary and will abort if it is present). It also does not support nested
dictionaries.

Say your_file.gypi looked like this:
  {
     'sources': [ 'a.cc', 'b.cc' ],
     'defines': [ 'ENABLE_DOOM_MELON' ],
  }

You would call it like this:
  gypi_values = exec_script("//build/gypi_to_gn.py",
                            [ rebase_path("your_file.gypi") ],
                            "scope",
                            [ "your_file.gypi" ])

Notes:
 - The rebase_path call converts the gypi file from being relative to the
   current build file to being system absolute for calling the script, which
   will have a different current directory than this file.

 - The "scope" parameter tells GN to interpret the result as a series of GN
   variable assignments.

 - The last file argument to exec_script tells GN that the given file is a
   dependency of the build so Ninja can automatically re-run GN if the file
   changes.

Read the values into a target like this:
  component("mycomponent") {
    sources = gypi_values.sources
    defines = gypi_values.defines
  }

Sometimes your .gypi file will include paths relative to a different
directory than the current .gn file. In this case, you can rebase them to
be relative to the current directory.
  sources = rebase_path(gypi_values.sources, ".",
                        "//path/gypi/input/values/are/relative/to")
"""

import gn_helpers
from optparse import OptionParser
import sys

def LoadPythonDictionary(path):
  file_string = open(path).read()
  try:
    file_data = eval(file_string, {'__builtins__': None}, None)
  except SyntaxError, e:
    e.filename = path
    raise
  except Exception, e:
    raise Exception("Unexpected error while reading %s: %s" % (path, str(e)))

  assert isinstance(file_data, dict), "%s does not eval to a dictionary" % path
  assert 'conditions' not in file_data, \
      "The file %s has conditions in it, these aren't supported." % path

  return file_data


def main():
  parser = OptionParser()
  (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])
  print gn_helpers.ToGNString(data)

if __name__ == '__main__':
  try:
    main()
  except Exception, e:
    print str(e)
    sys.exit(1)