Fix issue with importing packages where the package name included a dot

Fix issue with importing packages where the package name included a dot

The generated code for imports where just using the package name as
the prefix. This did not work if the package name included a dot. The
prefix is not generated by replacing dots with the dollar
character. The dollar character is valid in Dart identifiers but not
in protocol buffer package names so no name clashes should happen.

R=sigmund@google.com

Committed: https://github.com/dart-lang/protoc-plugin/commit/1f35d8b

[Siggi Cherem (dart-lang), 2014-01-08 21:35:33]

lgtm!

I assume these $ will be rarely seen by users, since this is just internal for
the generated code, right?

On the other hand, if that is a concern for some reason, another idea would be
to generate prefixes using a simple counter local to the generated file. So the
prefix name could be independent of the imported "package" name (you'd just use
p1, p2, p3.)

[Søren Gjesse, 2014-01-09 08:14:30]

On 2014/01/08 21:35:33, Siggi Cherem (dart-lang) wrote:
> lgtm!
> 
> I assume these $ will be rarely seen by users, since this is just internal for
> the generated code, right?
> 
> On the other hand, if that is a concern for some reason, another idea would be
> to generate prefixes using a simple counter local to the generated file. So
the
> prefix name could be independent of the imported "package" name (you'd just
use
> p1, p2, p3.)

The $ in the paxkage prefix is local to the .pb.dart file, and not visible
outside, so I think it is fine. It still makes the .pb.dart source more
readable. Also just generating prefix names might clash with other identifiers.

[Søren Gjesse, 2014-01-09 08:15:56]

Committed patchset #2 manually as r1f35d8b (presubmit successful).