Update to PostCSS 4.1

[davidtheclark]

It's nifty new messages API is well-suited to linting. If I understand correctly (still have to look into it more), we'd be able to accumulate all the errors and show them all at once to the user, instead of throwing one error at a time.

[MoOx]

That's exactly what I requested to @ai for stylelint and he loved the idea ;)

[davidtheclark]

After the discussion following this comment, I'm thinking that maybe what this linter could do for now (at least until something like stylelint is ready with a standard "linter" interface) is this:

• The plugin itself registers linting errors as PostCSS "warnings". Runners that follow the runner guidelines will print these in their own way.
• The npm package will also include a simple CLI that takes a glob of files, runs the linter on each, prints warnings, and throws an error if there are any warnings. A simple "reporter", I guess.

If we do those things I'm thinking we'd probably be well prepared to integrate with whatever comes later, while being able to use the thing now.

Would that fit your workflow @necolas? Do you have any disagreements?

[ai]

BTW, you can add some PostCSS plugin, that will throw a error if Result contains warnings from linter.

[davidtheclark]

Interesting idea @ai.

[necolas]

Sounds good to me

[MoOx]

I also plan to add the ability to lint files directly when @imported (would save some fs call). Using this API would help to defer all messages at the same moment (ref https://github.com/cssnext/cssnext/issues/64)