@rollup/plugin-typescript doesn't provide explicit file extension when format: 'esm' is used

[amannn]

• Rollup Plugin Name: @rollup/plugin-typescript
• Rollup Plugin Version: 12.1.1
• Rollup Version: 4.24.0
• Operating System (or Browser): macOS
• Node Version: 20
• Link to reproduction: https://github.com/amannn/ts-esm-test

Expected Behavior

@rollup/plugin-typescript should honor format: 'esm' and produce declaration files with explicit file extensions:

// dist/index.d.ts
export * from './core.js';

Actual Behavior

@rollup/plugin-typescript does not provide an explicit file extension in declaration files:

// dist/index.d.ts
export * from './core';

Additional Information

Note that for the JS output, this works as expected:

// index.js
export { test } from './core.js';

Reproduction:

1. Clone https://github.com/amannn/ts-esm-test/tree/main
2. pnpm i
3. pnpm build
4. pnpm lint (fails, as expected)

[drwpow]

Shouldn’t this be format: 'es'?