pubspec: detect two identical keys

[guillermooo]

I think pubspec-related linting is going to be handled by linter. If so, it could detect cases like this:

name: dart_sample_console
version: 0.0.1
description: A minimal command-line application.
environment:
  sdk: '>=1.0.0 <2.0.0'
dependencies:
  semver: '>=1.0.0 <2.0.0'
  semver: '>=0.1.0 <1.0.0'
dev_dependencies:
  unittest: any

However, I'm not sure how linter is intended to run (on demand, constantly in the background...). In this particular case, it would be useful if the user got instant feedback, as the analysis server provides for .dart files.

[guillermooo]

Moved from: dart-lang/dart_style#191

[pq]

Regarding how the linter is meant to run, there will be a few options. One of them will be interactively via the server. That's a little ways off but not too far.

As for the request, this is awesome. Keep 'em coming! :)