Make gn.py support root directories other than 'src'.

Make gn.py support root directories other than 'src'.

In https://codereview.chromium.org/341533006/ a change
was made so that gn.py is not looking for the .gn file
to identify the root of the checkout. This breaks
GN functionality for projects that uses gclient but
have a top directory named something else than 'src'.

This change adds support for arbitrarily named primary (the first)
solutions in the .gclient file.
It also adds a check for the generated GN path so a friendly
error message can be printed if the GN executable cannot be found.


BUG=389883
TESTED=Various cases of Chromium, WebRTC and custom checkouts
with .gclient containing empty solution list, solution missing the
'name' key and so on.

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=291819

[kjellander_chromium, 2014-09-05 07:03:31]

kjellander@chromium.org changed reviewers:
+ iannucci@chromium.org, maruel@chromium.org

[kjellander_chromium, 2014-09-05 07:03:32]

maruel and/or iannucci: please review

+cc brettw: FYI

[agable, 2014-09-05 11:31:53]

agable@chromium.org changed reviewers:
+ agable@chromium.org

[agable, 2014-09-05 11:31:54]

https://codereview.chromium.org/538393002/diff/1/gclient_utils.py
File gclient_utils.py (right):

https://codereview.chromium.org/538393002/diff/1/gclient_utils.py#newcode724
gclient_utils.py:724: if (env.has_key('solutions') and
I would rewrite this clause as:
solutions = env.get('solutions', [])
if solutions:
  return solutions[0].get('name')

I think this is easier to read than a triple conjunction, and it will default to
returning None if 'solutions' or 'name' don't exist.

https://codereview.chromium.org/538393002/diff/1/gn.py
File gn.py (right):

https://codereview.chromium.org/538393002/diff/1/gn.py#newcode30
gn.py:30: print >> sys.stderr, 'gn.py: Could not find gn executable at: %s' %
gn_path
return 1 after this print, for an unsuccessful exit, and so the subprocess.call
below doesn't have to be inside an else:.

[kjellander_chromium, 2014-09-05 12:24:32]

PTAL

https://codereview.chromium.org/538393002/diff/1/gclient_utils.py
File gclient_utils.py (right):

https://codereview.chromium.org/538393002/diff/1/gclient_utils.py#newcode724
gclient_utils.py:724: if (env.has_key('solutions') and
On 2014/09/05 11:31:53, agable wrote:
> I would rewrite this clause as:
> solutions = env.get('solutions', [])
> if solutions:
>   return solutions[0].get('name')
> 
> I think this is easier to read than a triple conjunction, and it will default
to
> returning None if 'solutions' or 'name' don't exist.

You're right. Covering the case with zero solutions in the list is highly
unlikely to happen.

https://codereview.chromium.org/538393002/diff/1/gn.py
File gn.py (right):

https://codereview.chromium.org/538393002/diff/1/gn.py#newcode30
gn.py:30: print >> sys.stderr, 'gn.py: Could not find gn executable at: %s' %
gn_path
On 2014/09/05 11:31:53, agable wrote:
> return 1 after this print, for an unsuccessful exit, and so the
subprocess.call
> below doesn't have to be inside an else:.

Done.

[agable, 2014-09-05 12:35:05]

LGTM

[kjellander_chromium, 2014-09-05 12:37:58]

The CQ bit was checked by kjellander@chromium.org

[commit-bot: I haz the power, 2014-09-05 12:38:49]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/kjellander@chromium.org/538393002/20001

[commit-bot: I haz the power, 2014-09-05 12:40:29]

Committed patchset #2 (id:20001) as 291819