Helper script which can source a bash script and dump environment as JSON.

build/env_dump.py

+#!/usr/bin/python
+# 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.
+
+# This script can either source a file and dump the enironment changes done by
+# it, or just simply dump the current environment as JSON into a file.
+
+import json
+import optparse
+import os
+import subprocess
+import sys
+
+
+def main():
+  parser = optparse.OptionParser()
+  parser.add_option('-f', '--output-json',
+                    help='File to dump the environment as JSON into.')
+  parser.add_option(
+      '-d', '--dump-mode', action='store_true',
+      help='Dump the environment to the file and exit immediately.')
+
+  options, args = parser.parse_args()
+  if not options.output_json:
+    parser.error('Requires --output-json option.')
+
+  if options.dump_mode:
+    if args:
+      parser.error("Cannot specify args with --dump-mode")
+    with open(options.output_json, 'w') as f:
+      json.dump(dict(os.environ), f)
+  else:
+    envsetup_cmd = ' '.join(args)

[Isaac (away), 2013/09/15 08:32:25]

' '.join(pipes.quote(a) for a in args) 

would be safer, in case args has any spaces or special characters.

[Isaac (away), 2013/09/15 08:34:02]

Or: ' '.join(map(pipes.quote, args))

[iannucci, 2013/09/15 09:16:47]

+1, I missed this.

+    full_cmd = [
+        'bash', '-c',
+        '. %s; ./%s -d -f %s' % (envsetup_cmd, __file__, options.output_json)]

[Isaac (away), 2013/09/15 08:32:25]

maybe the '.' at the beginning of line 37 should be passed as part of args,
rather than hard coded. wdyt?

[iannucci, 2013/09/15 09:16:47]

-1 on this. I would argue that the '.' (sourcing the file under bash) is part of
the implementation of this particular script.  We could also make this script
(for example):
  * Interpret the file directly.
  * Copy the file elsewhere and append our special dumper command, then invoke
the copy.

[Isaac (away), 2013/09/15 09:28:04]

:-D

+    ret = subprocess.call(full_cmd)
+    if ret:
+      sys.exit('Error running %s and dumping env', envsetup_cmd)

[Isaac (away), 2013/09/15 08:32:25]

AFAIK, sys.exit only takes one arg. Running new scripts through gpylint (or
maybe even the lenient chromium pylint) will catch this. Also might be cleaner
to use 

return '<str>' % envsetup_cmd

[iannucci, 2013/09/15 09:16:47]

Oh, yeah, sys.exit takes an error code, not a string...

[Isaac (away), 2013/09/15 09:28:04]

It actually can take a string (siva showed me this in a previous code review),
which is shorthand for print string to stderr, exit 1. But my local python fails
on 2 args.

[Siva Chandra, 2013/09/15 09:39:14]

sys.exit takes a string: http://docs.python.org/2.6/library/sys.html#sys.exit

This is clearly my bad, mixed up printf style syntax (',' for a '%') here.

Will send a CL to fix this and the above "quote" fix.

+
+
+if __name__ == '__main__':
+  sys.exit(main())