Error when trying to resolve augmented modules via --dts-only and --dts-resolve

[SplinterStan]

Problem

• When trying to generate DTS files for a specific module that depends on another module having it's types declared via module augmentation (declare module ...) results in an error.
• However, TypeScript compiler is able to resolve augmented modules.

Version info

• tsup 8.3.0
• typescript 5.6.3

Repro

1. Create a new package called tsup-augmented-module via npm init and put inside index.d.ts module augmentation, e.g.:

declare module "tsup-augmented-module" {

    export type SetupOptions = {
        token: string;
        someOtherOption?: number;
    };

}

2. Specify "types": "index.d.ts" in package.json.
3. Create another consumer module via npm init and put your augmented module as dependency:

"dependencies": {
  "tsup-augmented-module": "file:../tsup-augmented-module",
}

4. Now, in your index.ts write:

import { SetupOptions } from 'tsup-augmented-module';

export function test(options: SetupOptions): string {
  return 'test accomplished!';
}

5. Now, run npx tsup --entry index.ts --dts-only --dts-resolve and see an error like:

RollupError: "SetupOptions" is not exported by 'tsup-augmented-module', imported by "./index.ts".

Expectation

As typescript complier is able to resolve augmented modules, tsup should be able to as well.

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[unional]

I'm probably facing the same issue. There is the repro: https://github.com/repobuddy/storybook-image-snapshot

branch: rollup-dts

npm i
npm build

> tsup

CLI Building entry: src/index.ts
CLI Using tsconfig: tsconfig.json
CLI tsup v8.3.0
CLI Using tsup config: /home/unional/code/repobuddy/sis/tsup.config.ts
CLI Target: chrome100,safari15,firefox91,node18
CLI Cleaning output folder
ESM Build start
Generated an empty chunk: "index".
ESM dist/index.js     68.00 B
ESM dist/index.js.map 69.00 B
ESM ⚡️ Build success in 19ms
DTS Build start
node_modules/rollup/dist/rollup.d.ts (9:0): "Decorator" is not exported by "node_modules/@types/estree/index.d.ts", imported by "node_modules/rollup/dist/rollup.d.ts".
Error: error occured in dts build
    at Worker.<anonymous> (/home/unional/code/repobuddy/sis/node_modules/tsup/dist/index.js:1543:26)
    at Worker.emit (node:events:514:28)
    at MessagePort.<anonymous> (node:internal/worker:263:53)
    at [nodejs.internal.kHybridDispatch] (node:internal/event_target:814:20)
    at exports.emitMessage (node:internal/per_context/messageport:23:28)
DTS Build error

[unional]

Maybe related to #1231