Teach dart_package to understand the packages/ subdirectory

mojo/public/tools/dart_pub_get.py

+#!/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.
+
+# This script runs "pub get" on a given directory and outputs the filenames of

[tonyg, 2015/04/08 13:52:38]

This looks like a module-level docstring, """Lorem ipsum""", rather than a
comment, # Lorem ipsum.

[blundell, 2015/04/09 11:53:41]

Done.

+# the files that are thus pulled in relative to that given directory.

[tonyg, 2015/04/08 13:52:38]

I think a link to documentation would be helpful in this comment.
https://www.dartlang.org/tools/pub/get-started.html might be the most canonical?

[blundell, 2015/04/09 11:53:41]

Done.

+#
+# The first argument should be the parent directory of the Dart SDK relative to
+# the directory in which this script is being run.
+# The second argument should be the directory on which to run "pub get" relative
+# to the directory in which this script is being run.
+
+import os
+import subprocess
+import sys
+
+def main(args):
+  dart_sdk_root = args[0]

[tonyg, 2015/04/08 13:52:38]

This is a nit, but I'd recommend using argparse instead of manually pulling the
args. Then you can replace most of the usage comment above with structured usage
which is both obvious in code and from ./dart_pub_get.py --help.

[blundell, 2015/04/09 11:53:41]

Done.

+  target_directory = args[1]
+  cmd = [
+    os.path.join(os.getcwd(), dart_sdk_root, "dart-sdk/bin/pub")

[tonyg, 2015/04/08 13:52:38]

I could be mistaken, but I don't think os.getcwd() is what you actually want
here. That means this path'd be incorrect if this script was invoked from src/.

Instead, I think you want to grab the absolute path of this file and add the
appropriate number of os.pardir's to get back to src. Something like:
os.path.join(os.path.realpath(__file__), os.pardir, os.pardir, os.pardir,
dart_sdk_root, "")

[blundell, 2015/04/09 11:53:41]

Done.

+  ]
+  cmd.extend(["get"])
+
+  os.chdir(target_directory)
+  subprocess.check_output(cmd, shell=False, stderr=subprocess.STDOUT)

[tonyg, 2015/04/08 13:52:38]

Cleaner to pass cwd=target_dir rather than than doing an os.chdir on the line
above.

[blundell, 2015/04/09 11:53:41]

Done.

+
+  for root, _, files in os.walk("packages", followlinks=True):
+    for f in files:
+      print os.path.join(root, f)
+
+if __name__ == '__main__':
+  sys.exit(main(sys.argv[1:]))