Import types from mdast or add @types/unist to devDeps

[CanRau]

I think those types should probably be imported from 'mdast'
https://github.com/syntax-tree/unist-util-is/blob/master/index.d.ts#L3
Or as mentioned in the title @types/unist needs to be added to the dependencies

I'm trying to update to Yarn2 and this popped up

../../.yarn/cache/unist-util-is-npm-4.0.1-2754fc9f60-1.zip/node_modules/unist-util-is/index.d.ts(3,28): error TS2307: Cannot find module 'unist'.

and as Yarn2 is really specific about deps my only guess right now is this issue 😁

(edited by @wooorm to refactor formatting)

[ChristianMurphy]

I think those types should probably be imported from 'mdast'

I'm confused how mdast comes into the picture here.
The warning message you shared is related to unist.

Or as mentioned in the title @types/unist needs to be added to the dependencies

This is similar to syntax-tree/unist-util-filter#4

We've avoided adding direct dependencies on @types/ packages due to the issues outlined in unifiedjs/unified#45 .
When using Typescript add the unist typings using npm install --save-dev @types/unist or yarn add --dev @types/unist.

[CanRau]

Hum I see, my package has @types/unist already in devDeps. Yarn2 really expects every package specifying deps specifically itself tho.
Yea my fault mdast doesn't make sense here, not sure about my thinking back then 😅 I mis-looked and thought it'd export the needed types too for some reason..
So not sure how to proceed with yarn2 🤔 resolutions don't seem to work here

[ChristianMurphy]

Yarn 2 checks the typings during the install phase? Is that expected?
I haven't come across documentation briefly scanning the new docs at https://next.yarnpkg.com, do you happen to know if there is documentation for the new types/validation behavior?

Also note that Yarn 2 is still a pre-release there may be some bugs/instability.

[ChristianMurphy]

/cc @Rokt33r

[CanRau]

You're right it doesn't, that happened because of a postinstall script in the workspaces root.
Disabling it let me proceed with yarn install though trying to build those packages directly or using lerna later yields the same result.
As mentioned I've already got unist in local devDeps, moving to dependencies doesn't change.

Yea I know about pre-release, yet they mention the explicit dependency resolution everywhere so I doubt that'll change 🤷‍♂️

Forgot to link to https://yarnpkg.com/advanced/migration#a-package-is-trying-to-access-another-package-
Update
Okay so the in the link mentioned packageExtensions are at least a fix

packageExtensions:
  'unist-util-is@*':
    dependencies:
      '@types/unist': '*'

That seems to work

[ChristianMurphy]

Interesting, based off how that works.
It sounds like every project using Yarn 2, would need to:
Apply this patch for every package that relies on the typings for @types/unist and @types/vfile.

Which could be a lot when we get to the high level packages like remark/rehype/retext presets, which include many plugins, which include many utils, each of which will need to be patched.

It feels like a bad developer experience because it both takes patching, and the patching would need to happen at the nested/transitive dependency level, meaning devs need to dive deep into internals to get simple presets to work.