`declaration` option is not work when `package.json` set `exports.types`

Environment

Node.js: v20.10.0
pnpm: v8.15.5
unbuild: v2.0.0

Reproduction

Describe the bug

The option declaration do not do anything because in the end it will be set according to exports in package.json.

Describe Bug

declaration: false will not work:

import { defineBuildConfig } from 'unbuild'

export default defineBuildConfig({
  declaration: false,
})

When in package.json:

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

The declaration will be set true if the values of exports contains any files named *.d.(m|c)?ts in package.json.

Also, because of the same reason, declaration: 'node16' can not work too, it is same as true instead of the description in comments.

More details refer to:

https://github.com/unjs/unbuild/blob/bfb4a348421826ad48072ca1cf70973e6caa5b1d/src/auto.ts#L34

https://github.com/unjs/unbuild/blob/bfb4a348421826ad48072ca1cf70973e6caa5b1d/src/auto.ts#L154

Discussion

The problem is whether it is a bug or a deliberate design. I think when declaration is set as false explicitly, it should be false. It is counter-intuitive that set it as false but it still work. So in my option, user-initiated actions should have the highest priority.

Additional context

To fix it, refer to:

https://github.com/unjs/unbuild/blob/bfb4a348421826ad48072ca1cf70973e6caa5b1d/src/auto.ts#L34

If declaration is not undefined, it should use what user provided.

I am glad to provide a PR for that!

Logs

No response

unjs / unbuild