Add `ava/babel` as a shortcut for including AVA's Babel presets

[vadimdemedes]

It seems to be a good convention across the community (glamor, next.js, more) to provide a shortcut for auto-including Babel settings. If user wants to customize presets, right now he has to include these presets manually. What I'm proposing:

{
  "presets": [
    "ava/babel",
    "custom-preset"
  ]
}

It would also significantly simplify the creation of tools like ava-preact-init, ava-react-init, ava-inferno-init, etc. If we provide a simple entrypoint for these presets, we won't need to update each of these modules when we change something in our presets.

[novemberborn]

We have @ava/stage-4 and @ava/transform-test-files now. What are you proposing @ava/babel does?

[vadimdemedes]

No, not @ava/babel package, but ava/babel.js file. This file would simply serve as a preset, which would include @ava/stage-4 and @ava/transform-test-files. Think of it as a handy shortcut, nothing more.

[novemberborn]

Ah. I think we should wait and see how the new presets get used, especially as we improve our Babel support.

[vadimdemedes]

I think we should wait and see how the new presets get usedI think we should wait and see how the new presets get used

Could you explain that more? I didn't get the point.

[novemberborn]

See if and how people use @ava/stage-4 / @ava/transform-test-files, without adding a wrapper preset to AVA itself.

[novemberborn]

Turns out a preset like this is suggested in RFC 001:

testOptions: {}: specify the Babel options used to compile test and helper files. If provided this completely disables the default Babel configuration AVA uses to compile test and helper files. Like with sourceOptions, babelrc defaults to true. Set presets: ["ava"] to apply AVA's transforms.

Though I suspect we may have to parse the options looking for that preset, and then replacing it with @ava/stage-4 and @ava/transform-test-files. The latter taking the power-assert option into account.

[novemberborn]

#1608 implements ava/stage-4 as an alias for our @ava/stage-4 preset. I've decided not to expose @ava/transform-test-files as I want to (conceptually at least) separate the enhancements it contains from AVA's Babel usage.