Fix dual emit declaration files

[andrewbranch]

tsup just published egoist/tsup#934, which fixes a module format agreement issue that you inherited from its output. Details in the tsup PR, but:

Before

🎭 Import resolved to a CommonJS type declaration file, but an ESM JavaScript file.
https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/FalseCJS.md

🐛 Import resolved to types through a conditional package.json export, but only after
failing to resolve through an earlier condition. This behavior is a TypeScript bug. It
may misrepresent the runtime behavior of this import and should not be relied upon.
https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/FallbackCondition.md


┌────────────────────┬───────────────────────────────────┬───────────────────────────────────┐
│                    │ "@total-typescript/shoehorn"      │ "@total-typescript/shoehorn/pack… │
├────────────────────┼───────────────────────────────────┼───────────────────────────────────┤
│ node10             │ 🟢                                │ 🟢 (JSON)                         │
├────────────────────┼───────────────────────────────────┼───────────────────────────────────┤
│ node16 (from CJS)  │ 🟢 (CJS)                          │ 🟢 (JSON)                         │
├────────────────────┼───────────────────────────────────┼───────────────────────────────────┤
│ node16 (from ESM)  │ 🎭 Masquerading as CJS            │ 🟢 (JSON)                         │
│                    │ 🐛 Used fallback condition        │                                   │
├────────────────────┼───────────────────────────────────┼───────────────────────────────────┤
│ bundler            │ 🐛 Used fallback condition        │ 🟢 (JSON)                         │
└────────────────────┴───────────────────────────────────┴───────────────────────────────────┘

After

❯ npm run attw                          

> @total-typescript/shoehorn@0.1.1 attw
> attw --pack


 No problems found 🌟


┌────────────────────┬───────────────────────────────────┬───────────────────────────────────┐
│                    │ "@total-typescript/shoehorn"      │ "@total-typescript/shoehorn/pack… │
├────────────────────┼───────────────────────────────────┼───────────────────────────────────┤
│ node10             │ 🟢                                │ 🟢 (JSON)                         │
├────────────────────┼───────────────────────────────────┼───────────────────────────────────┤
│ node16 (from CJS)  │ 🟢 (CJS)                          │ 🟢 (JSON)                         │
├────────────────────┼───────────────────────────────────┼───────────────────────────────────┤
│ node16 (from ESM)  │ 🟢 (ESM)                          │ 🟢 (JSON)                         │
├────────────────────┼───────────────────────────────────┼───────────────────────────────────┤
│ bundler            │ 🟢                                │ 🟢 (JSON)                         │
└────────────────────┴───────────────────────────────────┴───────────────────────────────────┘

I’ve also taken the liberty of including this check as part of your release process, since unlike tsc, tsup does not actually check that the output is actually valid in all these scenarios.

[andrewbranch]

We’re letting extension substitution do the work here, but if you want to be explicit about specifying types, this has the same outcome:

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

[mattpocock]

You'll need to add attw to turbo.json to get this working I think.

What outputs does attw --pack have?

[andrewbranch]

Just an exit code (and stdout whether it succeeds or fails, but only interesting in CI if you need to look at why it failed). It runs npm pack but deletes the file after checking it.

[mattpocock]

Wow, pal - thanks so much for making this change on this repo.

Small changes needed to turbo.json, outlined in comment.

[andrewbranch]

Sure thing! I discovered recently that you were a tsup user, so I figured something like this would be a good way to prove out the tsup change I made on something real, and be able to link to it as an example of how to take advantage of the new output, since a small package.json change is necessary.

[mattpocock]

Looks great, thanks pal!