Is it possible to bundle type declarations from dependencies in the same way as code?

[delucis]

When importing a devDependency (or a dependency specified in the deps.alwaysBundle option), tsdown will bundle the code of that dependency into the build output.

However, if you also depend on some types provided by that dependency, e.g. import type { example } from 'some-bundled-dep', as far as I can tell, the build will always fail if trying to generate type declaration files, e.g. the build will fail with a message like

   ╭─[ src/example.d.ts:1:10 ]
   │
 1 │ import { example } from "some-bundled-dep";
   │          ───┬───  
   │             ╰─── Missing export
   │ 
   │ Note: If you meant to import a type rather than a value, make sure to add the `type` modifier (e.g. `import { type Foo } from 'some-bundled-dep'`).
───╯

(The logged error suggests the type modifier is missing, but it isn’t in this case — I assume it is being stripped at some other point in the build process.)

Would it be possible to have DTS generation behave like the code bundling does and bundle the required declarations in this case? I tried both with the oxc-transform approach using isolatedDeclarations and with typescript itself, but get the same result in both cases.

[sxzz]

It's supported by default, but cjs dts is not supported. Please provide the minimal reproduction.

[delucis]

Oh interesting! Maybe it is a CJS issue then, not sure 🤔

Here’s a minimal repro with the package I was hitting the issue with: https://stackblitz.com/edit/github-i7hgbdhy?file=src%2Findex.ts

[sxzz]

declare module '...' is not supported.