How to fix gn Unexpected token error

Today I encountered a strange error when I try to compile latest android-chromium.


$gn gen --args='target_os="android"' out/Default
ERROR at //.gn:30:16: Unexpected token '{'
default_args = {
               ^


$vim .gn
29 # additional logic required by Chrome to set the variables.
30 default_args = {
31   v8_extra_library_files = [

It is very strange, the .gn file looks well.
then I doubt the program comes from gn tool.
$ which gn
/home/lenger/depot_tools/gn

$vim /home/lenger/depot_tools/gn
#!/usr/bin/env bash
# Copyright 2013 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.

base_dir=$(dirname "$0")

PYTHONDONTWRITEBYTECODE=1 exec python "$base_dir/gn.py" "$@"

gn just a python wrapper. let's check where the real gn tool is.
$vim /home/lenger/depot_tools/gn.py
def main(args):
  bin_path = gclient_utils.GetBuildtoolsPlatformBinaryPath()
  if not bin_path:
    print >> sys.stderr, ('gn.py: Could not find checkout in any parent of '
                          'the current path.\nThis must be run inside a '
                          'checkout.')
    return 1
  gn_path = os.path.join(bin_path, 'gn' + gclient_utils.GetExeSuffix())
  print (gn_path)
  if not os.path.exists(gn_path):
    print >> sys.stderr, 'gn.py: Could not find gn executable at: %s' % gn_path
    return 2
  else:
    return subprocess.call([gn_path] + args[1:])

The red line was added by me to debug the real gn path.
Then let's run gn command
$gn
/home/lenger/commontrunk/chromium/src/buildtools/linux64/gn
ERROR No command specified.

Ok then I found the cause. the gn tool is in another chromium repo.
It is not in my latest android-chromium and not the latest one.

let's figure out why the build tool select like this.
$vim /home/lenger/depot_tools/gn.py
def main(args):
  bin_path = gclient_utils.GetBuildtoolsPlatformBinaryPath()  
$ vim ~/depot_tools/gclient_utils.py
def GetBuildtoolsPath():
  """Returns the full path to the buildtools directory.
  This is based on the root of the checkout containing the current directory."""

  # Overriding the build tools path by environment is highly unsupported and may
  # break without warning.  Do not rely on this for anything important.
  override = os.environ.get('CHROMIUM_BUILDTOOLS_PATH')
  if override is not None:
    return override

  primary_solution = GetPrimarySolutionPath()
  if not primary_solution:
    return None
  buildtools_path = os.path.join(primary_solution, 'buildtools')
  if not os.path.exists(buildtools_path):
    # Buildtools may be in the gclient root.
    gclient_root = FindGclientRoot(os.getcwd())
    buildtools_path = os.path.join(gclient_root, 'buildtools')
  return buildtools_path


def GetBuildtoolsPlatformBinaryPath():
  """Returns the full path to the binary directory for the current platform."""
  buildtools_path = GetBuildtoolsPath()
  if not buildtools_path:
    return None

I found it.
env CHROMIUM_BUILDTOOLS_PATH  might override the build tool path.
then I check my env:

$ env | grep BUILD
CHROMIUM_BUILDTOOLS_PATH=/home/lenger/commontrunk/chromium/src/buildtools/ 

Oh. I remember now, I had set this env a long time ago in my .bashrc.





I make this strange error by myself.
Ok. easy to fix it now. just unset that env.
$unset  CHROMIUM_BUILDTOOLS_PATH

Let's try  gn again
$gn gen --args='target_os="android"' out/Default
/home/lenger/android_chromium/src/buildtools/linux64/gn
Done. Made 13942 targets from 1133 files in 6795ms








Good. Everything goes well now.