Fix missing types from exports

[JAD3N]

No description provided.

[lupomontero]

Hi @JAD3N, thanks for the PR 💪

I'm not that familiar with TypeScript 🙈, and I'm a bit confused by this change 😰

Your change adds exports.*.types to package.json. Something like:

{
  "exports": {
    ".": {
      "types": "./types/index.d.ts",
      "import": "./dist/psl.mjs",
      "require": "./dist/psl.cjs"
    }
  }
}

However, in the TypeScript docs I can only find a mention to types (which is already present in psls package.json).

On the other hand, doing a bit of research, I found some info in the release notes for typescript@4.7 as well as an "official" blog post announcing that same version. In both the following kind of setup is suggested.

{
  "exports": {
    ".": {
      "import": {
        "types": "./types/index.d.ts",
        "default": "./dist/psl.mjs"
      },
      "require": {
         "types": "./types/index.d.ts",
        "default":  "./dist/psl.cjs"
      }
    }
  }
}

Can you shed some light on this? Are you familiar with the stuff mentioned above? I'd really like to understand the implications in depth before we merge the PR.

[JAD3N]

Hi @lupomontero,

I believe the exports.*.types property is a "community condition definition" which TypeScript uses for retrieving typings of specific conditional exports of imported packages/modules when type-checking.

This depends on the version of TypeScript and the configured module resolution. This link here clarifies that the newer "bundler" module resolution utilizes conditional exports, so we would want to keep the current types and add the exports.*.types as well for full compatibility.

I'm not too sure on whether it needs separate typing files for ESM & CJS, I'm using mostly ESM nowadays, so I've not encountered an issue regarding this. It may be worth adding an additional typings file for CJS as well, I think that would just change things to export via module.exports , but I'm unsure which one you would use in the root types property in the package.json.

Edit: From what I can find out here it seems that the existing and this PR's typing file appear to be compatible with both but more research might be needed to clarify.

Edit 2: Another link I've found that might be more useful: https://www.typescriptlang.org/docs/handbook/modules/appendices/esm-cjs-interop.html#allowsyntheticdefaultimports-and-esmoduleinterop

[JAD3N]

Hi @lupomontero,

I did a bit more research and there should only be issues requiring separate typings (for CJS & ESM) when utilizing default exports and named exports. Since we're only utilizing named exports there shouldn't be any problems. If we did have a default exports in the typings with named exports, then we would utilize the config option mentioned above (esModuleInterop) to resolve it.

Do you need any more details to get this merged? Let me know.