Default lib values don't work with the programmatic TS API

[tylerlaprade]

Hey! I ran into an issue with the default compilerOptions.lib values in expressive-code-twoslash.

The defaults are set to:

lib: ["Bundler", "ES2022", "DOM", "DOM.Iterable"]

But the TypeScript programmatic API (used by @typescript/vfs under the hood) needs the file path format for lib names — e.g. "lib.es2022.d.ts", "lib.dom.d.ts", etc. The friendly names like "ES2022" and "DOM" only work in tsconfig.json because tsc normalizes them internally before calling the compiler API.

Since twoslash goes through the programmatic API directly, these values are silently ignored, which means DOM types (and ES2022 types) aren't actually loaded by default. I only noticed because code blocks using DOM APIs were getting type errors.

Also, "Bundler" isn't a valid lib name at all — it's a moduleResolution value.

The fix on my end was overriding lib in the config:

ecTwoSlash({
  twoslashOptions: {
    compilerOptions: {
      lib: ["lib.esnext.full.d.ts"],
    },
  },
})

But it'd be nice to have the defaults just work. The correct values would be something like:

lib: ["lib.es2022.d.ts", "lib.dom.d.ts", "lib.dom.iterable.d.ts"]

Thanks for the great plugin!

[Adammatthiesen]

Hey @tylerlaprade! I admit i built this back with around 6 months of TypeScript knowledge under my belt so it makes perfect sense now that i am thinking about everything i've learned since then... I'll be fixing this and a few other things here soon! Right now i am prepping to transfer this project into the @withstudiocms GitHub org! (I am a founder and core maintainer of that org)

Thanks for the tip! And hope to see more of you in the other org! (Repo transfer should be happening in the next 24-72 hours)