Enable Dart 2.0 support

[Stargator]

Since this project provides the web_server executable, I need to update it for Dart 2.0

Dependent on the following PRs in other repos:

• Enable support for Dart 2.0 cache#2
• Enable Dart 2.0 support event-listener#1
• Enable Dart 2.0 support server-logger#1

[bwhite000]

Hi @Stargator! Thank you so much for the work and contributions that you've done! I wasn't aware that my project had any current users until recently. I'll start up working on it again with ways that I have learned to write better code since the last commit.

I'll start reviewing your pull request after work this afternoon. Please know that I greatly appreciate your efforts and that any comments that I make aren't detracting from that appreciation at all :)

[bwhite000]

I'll make a note here, too, to change supporting code so that this can be typed again in the parameter field under Dart 2.0.

[bwhite000]

@Stargator, I left some comments and praises in the GitHub review. Thanks again a million for the contributions!

[bwhite000]

I'll review the pull requests in the other dependent packages as soon as I next can 👍

[Stargator]

@bwhite000 Ready for a re-review!

[Stargator]

@bwhite000 I have added a change that is based on a PR for dart2_constant.

Those changes added io.HttpHeaders. Currently, dart2_constant doesn't support that. I'm working to fix that.

[Stargator]

Nevermind, I removed those changes. I can incorporate it once dart2_constant is updated.

[Stargator]

@bwhite000 I set it up so web_server and cache both use my fork of dart2_constant. The package has been archived by the Dart Team. I'm hoping to convince them to let me be the primary maintainer.

[Stargator]

@bwhite000 Are you able to review the changes I made to your feedback?

Note that it is dependent on the other PRs in the original post being approved and merged for those dependent packages.

[Stargator]

@bwhite000 Do note, the Dart SDK has made changes to what kind of dependencies new versions of a package can have on pub.dev. See dart-lang/sdk#36765.

From what I see, web-server and cache depend on my forked version of dart2_constant.

So either:

1. You can merge in the changes before the next release of Dart that contains the new rule.
   • Then later you bump the version and drop Dart 1 support, thus drop the need for dart2_constant.
2. I publish the forked version to pub.dev.