`@typescript-eslint/parser` breaks XO #555

// @Richienb I think this is related to recent changes as it only happened when upgrading XO.

I wonder why this problem only appears on Node.js 12 and 14 but not on 16. Perhaps a different module resolution algorithm is actually able to find the typescript module or npm is installing it in a slightly different path.

I think I have figured it out. Node.js 16 passes because it has npm 7 which install peer dependencies by default. I'm hoping https://github.com/xojs/eslint-config-xo-typescript/commit/2e16d51a8cdcd1e34a827fa8e782075888590062 will fix the issue on other Node.js versions.

Did not work...

@Richienb We need to find a workaround for now. npm 6 will be with us for as long as Node.js 14, which means years.

One idea I had was to add a postinstall script to XO that installs typescript into node_modules/@typescript-eslint/parser

Related issue: https://github.com/typescript-eslint/typescript-eslint/issues/828

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I think a solution to this problem would be to ship xo with a npm-shrinkwrap.json as it would then work like a package-lock.json during installation and ensure that everything gets installed as intended: https://docs.npmjs.com/cli/v7/configuring-npm/package-lock-json#package-lockjson-vs-npm-shrinkwrapjson

I dug waaaaaaay too deep into this and can now say why this error happens:

The part of npm 6.x that's responsible for deduping the three is earliestInstallable().

In that function there are a couple of checks to see if a module can be added earlier, and one of those checks are a check for conflicting binaries.

It bails on typescript for p-cancelable and the reason is: tsd

Since tsd has already hoisted @tsd/typescript (I believe npm processes dependencies in alphabetic order) it blocks the hoisting of typescript as they both (one being the fork of the other) exposes the same binaries.

I removed tsd from p-cancelable and did a fresh install and verified that typescript then gets correctly hoisted on npm 6.x.

There is a PR to solve this in @tsd/typescript: https://github.com/SamVerschueren/tsd-typescript/pull/3 And an issue in tsd about it: https://github.com/SamVerschueren/tsd/issues/122

If that PR gets merged and released, then as soon as p-cancelable picks up that new release, then tests will start working on with npm 6 again.

Though: Especially considering that xo, due to being pretty much last in the alphabet, is doomed to pretty much always be processed last, any other module before it that contains a binary conflict with typescript will stop typescript from being hoisted while the modules that requires typescript will still get hoisted.

The solutions to that is as said in previous comment: npm-shrinkwrap.json Or add them as bundledDependencies, though the latter will actually bundle those dependencies within the xo bundle on npm, creating quite a bit larger bundle for xo

Since this isn't a browser-based tool, it could probably work to add them to bundledDependencies since size doesn't matter as much.

@voxpelli That is some incredible investigation. Thanks for looking into this. 🙌

I think we should use bundleDependencies. That way we are safe from this happening in the future. We can drop the bundleDependencies one day when we target Node.js 16.

@sindresorhus I have created a PR that should make this work 👍

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