Monday, January 7, 2013

Dart Lands First Set of Library v2 Changes

The first big set of "Dart library v2" changes landed in the bleeding_edge branch today, which means it's time to investigate changes required to your code and pub packages. Further details about the changes, along with tips for updating, are forthcoming. For now, here's what you, our intrepid Dart developers, need to know.



The biggest changes are to async and collections

Everyone's first question: so, what's new? Until we publish a more comprehensive list of changes, here's a short, incomplete list to wet your whistle:

  • The new dart:async library now contains Future, Timer, and Streams.
  • The Future class changed quite a bit. For example, chain and transform are now simply then.
  • The new dart:collection library has more functionality beyond the basics found in dart:core.
  • The Iterator class changed, with new methods moveNext() and current. Many new operations, and some old ones, work with Iterable.
  • List gets two new named constructors: List.fixedLength(length, {fill}) and List.filled(len, fill).
  • Lots more...

The bleeding_edge docs are available for further exploration. To be clear, there are more changes than what is listed above. A more detailed post is on its way.

The M2 build is stable for 2-3 weeks

If you use the M2 build (essentially the latest Editor build, revision 0.2.9 or 0.2.10), you are insulated from these changes for now. We do not intend to push the library changes to the Editor builds for at least two weeks. This gives us enough time to update internal and external packages pushing out a new build.

Docs for M2 libraries are now available

You can now access API docs that match the shipping version of the SDK and Editor. The api.dartlang.org site now redirects to api.dartlang.org/docs/releases/latest/ which tracks the version of the SDK that ships in the editor's (mostly) weekly releases. The bleeding_edge docs are still available, if you want to see what's coming up.


Lock your pubspec.yaml file, or avoid updates, for 2-3 weeks

If you use pub to integrate third-party libraries, we advise you to do one of the following to minimize risk of a breaking change:

  • Avoid running pub update until after you get a new version of the stable Editor and SDK. This will probably be 2-3 weeks from now.
  • Manually lock the versions of your dependencies, by updating your pubspec.yaml and using specific version numbers instead of the any keyword.

The bleeding_edge branch is a moving target

The bleeding_edge branch, which is where all these library changes are getting merged, is going to take a few days to settle down. If you're experimenting with Dart's SVN repository or otherwise working with bleeding_edge, be warned. We're not quite done with the merge, and we have tests to fix.

Pub authors: Learn about the new changes

If you are the author of one or more pub packages, now is a great time to learn about these changes. Wait until our build bots turn green, and then you can download a bleeding_edge build to try it out. Meanwhile, you can view the bleeding_edge docs. Fear not, you can install the bleeding_edge version alongside your M2 build.

Thank you for your patience and feedback


We know these changes cause work for all of you, our developers. Our aim is to respond to feedback now, and make these changes as quickly as we can, so we can get to 1.0 and a more stable Dart. Thank you for your patience. We look forward to your feedback on the mailing list, and your bug reports and feature requests at dartbug.com.


(Image courtesy of http://www.flickr.com/photos/vblibrary/4419780791/)