Add FromGNArgs() to gn_helpers.

Add FromGNArgs() to gn_helpers.

This adds a method to convert a string containing a list of
gn --args -like assignments to a python dict.

(ToGNString() already supports the opposite direction).

R=brettw@chromium.org, hashimoto@chromium.org
BUG=561142
Committed: https://crrev.com/65d84dc0f629632d10687e2c85e8eea55362dc5d
Cr-Commit-Position: refs/heads/master@{#385336}

[Dirk Pranke, 2016-04-02 00:01:03]

This is needed in the cros_chrome_sdk.py conversions between
ChromeOS build args and GN args ; see 

https://chromium-review.googlesource.com/#/c/332922/

for the context.

I thought about changing FromGNString() to just handle
whitespace-separated var=val lists as well, but it seemed
like that would badly conflate the two purposes, so I added
a new routine instead.

[brettw, 2016-04-05 19:25:28]

https://codereview.chromium.org/1847333005/diff/1/build/gn_helpers.py
File build/gn_helpers.py (right):

https://codereview.chromium.org/1847333005/diff/1/build/gn_helpers.py#newcode210
build/gn_helpers.py:210: val = self._ParseAllowTrailing(lists_are_allowed=False)
It seems like you go through some effort here to disallow lists, but I would
prefer it if lists are allowed. Can list_are_allowed just be removed?

[Dirk Pranke, 2016-04-05 19:28:42]

https://codereview.chromium.org/1847333005/diff/1/build/gn_helpers.py
File build/gn_helpers.py (right):

https://codereview.chromium.org/1847333005/diff/1/build/gn_helpers.py#newcode210
build/gn_helpers.py:210: val = self._ParseAllowTrailing(lists_are_allowed=False)
On 2016/04/05 19:25:27, brettw wrote:
> It seems like you go through some effort here to disallow lists, but I would
> prefer it if lists are allowed. Can list_are_allowed just be removed?

I don't remember exactly now, but I have a vague memory that allowing lists
introduced some sort of complication. But I was probably thinking of something
else.

Regardless, I don't know of any actual GN args (in the declare_args() sense)
that are actually lists, so it seems like allowing them could just lead to bugs
showing up down the road in weird ways.

But, yes, I can certainly just allow them for now and see what happens.

[brettw, 2016-04-05 22:35:42]

> But, yes, I can certainly just allow them for now and see what happens.

Yes, I think restricting them in this one particular and very specific case
seems arbitrarily weird. If there are reasons we shouldn't support them, they
should be restricted in all cases, and I'm not aware of any problems.

[Dirk Pranke, 2016-04-05 23:31:23]

updated; please take another look?

[brettw, 2016-04-05 23:32:10]

lgtm

[Dirk Pranke, 2016-04-05 23:32:25]

The CQ bit was checked by dpranke@chromium.org

[commit-bot: I haz the power, 2016-04-05 23:32:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1847333005/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1847333005/20001

[commit-bot: I haz the power, 2016-04-05 23:35:08]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-04-05 23:35:09]

Try jobs failed on following builders:
  win_chromium_rel_ng on tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_rel_...)

[Dirk Pranke, 2016-04-05 23:37:38]

The CQ bit was checked by dpranke@chromium.org

[commit-bot: I haz the power, 2016-04-05 23:38:05]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1847333005/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1847333005/20001

[commit-bot: I haz the power, 2016-04-06 00:08:22]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-04-06 00:10:48]

Description was changed from

==========
Add FromGNArgs() to gn_helpers.

This adds a method to convert a string containing a list of
gn --args -like assignments to a python dict.

(ToGNString() already supports the opposite direction).

R=brettw@chromium.org, hashimoto@chromium.org
BUG=561142
==========

to

==========
Add FromGNArgs() to gn_helpers.

This adds a method to convert a string containing a list of
gn --args -like assignments to a python dict.

(ToGNString() already supports the opposite direction).

R=brettw@chromium.org, hashimoto@chromium.org
BUG=561142

Committed: https://crrev.com/65d84dc0f629632d10687e2c85e8eea55362dc5d
Cr-Commit-Position: refs/heads/master@{#385336}
==========

[commit-bot: I haz the power, 2016-04-06 00:10:49]

Patchset 2 (id:??) landed as
https://crrev.com/65d84dc0f629632d10687e2c85e8eea55362dc5d
Cr-Commit-Position: refs/heads/master@{#385336}