Improve pub's pubspec error messages.

Improve pub's pubspec error messages.

This uses the source spans exposed by the yaml package to associate pubspec
errors visually with the section of the pubspec that caused them.

R=rnystrom@google.com
BUG=14999
Committed: https://code.google.com/p/dart/source/detail?r=37675

[Bob Nystrom, 2014-06-24 20:49:07]

LGTM!

https://codereview.chromium.org/351703004/diff/1/sdk/lib/_internal/pub/lib/sr...
File sdk/lib/_internal/pub/lib/src/barback/transformer_config.dart (right):

https://codereview.chromium.org/351703004/diff/1/sdk/lib/_internal/pub/lib/sr...
sdk/lib/_internal/pub/lib/src/barback/transformer_config.dart:77: }
I don't think I realized we don't allow arbitrarily nested data for transformer
configs. Is that documented anywhere? Any reason for the limitation?

[nweiz, 2014-06-24 20:50:40]

https://codereview.chromium.org/351703004/diff/1/sdk/lib/_internal/pub/lib/sr...
File sdk/lib/_internal/pub/lib/src/barback/transformer_config.dart (right):

https://codereview.chromium.org/351703004/diff/1/sdk/lib/_internal/pub/lib/sr...
sdk/lib/_internal/pub/lib/src/barback/transformer_config.dart:77: }
On 2014/06/24 20:49:07, Bob Nystrom wrote:
> I don't think I realized we don't allow arbitrarily nested data for
transformer
> configs. Is that documented anywhere? Any reason for the limitation?

This function is just for parsing $include and $exclude. General config stuff
can be arbitrarily nested.

[nweiz, 2014-06-24 21:43:42]

I realized I forgot to fix up the tests when I sent this out. PTAL :p

[Bob Nystrom, 2014-06-24 21:48:23]

One request but still LGTM!

https://codereview.chromium.org/351703004/diff/20001/sdk/lib/_internal/pub/te...
File sdk/lib/_internal/pub/test/get/git/dependency_name_match_pubspec_test.dart
(right):

https://codereview.chromium.org/351703004/diff/20001/sdk/lib/_internal/pub/te...
sdk/lib/_internal/pub/test/get/git/dependency_name_match_pubspec_test.dart:31:
'doesn\'t match expected name "weirdname".'));
Nit, but I think we usually put the exit code param after the error.

[nweiz, 2014-06-24 23:52:19]

https://codereview.chromium.org/351703004/diff/20001/sdk/lib/_internal/pub/te...
File sdk/lib/_internal/pub/test/get/git/dependency_name_match_pubspec_test.dart
(right):

https://codereview.chromium.org/351703004/diff/20001/sdk/lib/_internal/pub/te...
sdk/lib/_internal/pub/test/get/git/dependency_name_match_pubspec_test.dart:31:
'doesn\'t match expected name "weirdname".'));
On 2014/06/24 21:48:23, Bob Nystrom wrote:
> Nit, but I think we usually put the exit code param after the error.

Done.

[nweiz, 2014-06-24 23:54:09]

Committed patchset #3 manually as r37675 (presubmit successful).