src/build/run_python

#!/usr/bin/python
#
# Copyright 2015 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.

"""Simple wrapper of 'python' to run ARC Python scripts.

To run Python scripts in ARC properly, it is necessary to set up paths
of modules in advance. There are several ways for Python to set them,
but the best way is setting them up before starting the python interpreter.
Otherwise, we would hit some mysterious import errors, or need more hacky
workarounds.

This script wraps the 'python' command, and sets up PYTHONPATH just before
executing it.
"""

import os
import sys


_PYTHONPATH_LIST = [
    # Set ARC_ROOT to the PYTHONPATH.
    '',

    # For create_nmf.
    'third_party/chromium-ppapi/native_client_sdk/src/tools',

    # For PPAPI ARM floating point shim generation and PPAPI mocks.
    'third_party/chromium-ppapi/ppapi/generators',

    'third_party/pylib/beautifulsoup4',
    'third_party/pylib/sourcemap',
    'third_party/tools/depot_tools',
    'third_party/tools/ninja/misc',  # For ninja_syntax used in ninja_generator.
    'third_party/tools/python_mock',  # For testing.
]

_ARC_ROOT = os.path.normpath(os.path.join(
    os.path.dirname(os.path.realpath(__file__)), '..', '..'))


def _setup_pythonpath(env):
  """Adds (or overwrites) PYTHONPATH in |env|."""
  # Set absolute paths for PYTHONPATH.
  pythonpath_list = [os.path.normpath(os.path.join(_ARC_ROOT, path))
                     for path in _PYTHONPATH_LIST]
  original_pythonpath = env.get('PYTHONPATH')
  if original_pythonpath:
    pythonpath_list.extend(original_pythonpath.split(os.pathsep))
  env['PYTHONPATH'] = os.pathsep.join(pythonpath_list)


def main():
  # Set PYTHONPATH properly.
  env = dict(os.environ)
  _setup_pythonpath(env)

  # Run python executable directly. Note that we should not execute the python
  # script directly, even if its executable bit is set, because, on Chrome OS,
  # such a file is on the "noexec" file system.
  args = sys.argv[:]
  args[0] = sys.executable
  os.execve(args[0], args, env)


if __name__ == '__main__':
  main()