fix: add "types" field to package.json

[dominikg]

So that older versions of typescript without support for exports map are able to resolve types correctly.

see sveltejs/svelte#8362 for an example where it failed

[dominikg]

you may be able to remove typings from package.json, but I left it untouched in case it's used by other tooling i'm not aware of.

[benmccann]

Removing typings would make sense to me

[jridgewell]

Hi all, I haven't merged this yet because I want to redo the way types are discovered according to https://twitter.com/atcb/status/1634653545407610880

[dominikg]

hmmm, index.d.cjs is a thing? a recent ts version added .d.cts, but never heard of .d.cjs before.

Is that supported by old versions of typescript too?

And is it resolved/found even if an exports map exists that does not export it?

while specifying "types" in package.json twice is a bit redundant, it allows for wide compatibility without a need to change anything else.

[benmccann]

That advice seems quite surprising to me. I've also never seen it. If I do a Google search for "index.d.cjs" there's only two results and one is that Tweet

while specifying "types" in package.json twice is a bit redundant, it allows for wide compatibility without a need to change anything else.

I don't understand why you'd specify types and typings. Aren't they the same except types works in all versions and typings just in some? Why not just use types alone?

[dominikg]

i meant "types":"..." being duplicated inside and outside of exports.

if you have a top level "types", "typings" is indeed not needed for typescript itself, so can be removed if no other tool needs it. Im not aware of one, but also not familiar with why "typings" exists in the first place so not 100% sure

[benmccann]

Ah, thanks for clarifying. types and typings are synonymous: https://www.typescriptlang.org/docs/handbook/declaration-files/publishing.html#including-declarations-in-your-npm-package

The other way to deal with this if you want to modernize the package would just be to specify "type": "module" and get rid of the UMD distribution. That would cut the package in half and simplify things quite a bit.

[jridgewell]

@andrewbranch does your advice hold for earlier TS versions as well? Or does it only work for more recent ones with support for .cjs, .cts, etc?

[andrewbranch]

1. .d.cjs was a typo 🤦 It was supposed to be .d.cts
2. Nothing I suggested will break older versions of TypeScript, but a lot of the content is specific to doing the right thing for --module nodenext.

[benmccann]

Note that .d.cts only was introduced in TypeScript 4.7 (source) and most users don't use nodenext

It seems safest to me to just replace typings with types