[Feature]: Add an option to automatically generate exports fields in package.json

[Karibash]

What problem does this feature solve?

Currently, rslib aims for a zero-configuration experience by treating package.json as the single source of truth (see #62).
However, since rslib does not exclude *.test.ts files by default, it’s difficult to achieve a truly configuration-free setup.

To improve this, it would be helpful to introduce an option that automatically generates the following fields in package.json based on the build entries:

• main
• module
• types
• exports

This would make the build output and package metadata consistent without requiring manual edits to package.json.

For reference, tools like tsdown already provide a similar feature that derives these fields from the build entry configuration.
Implementing something comparable in rslib would simplify the developer experience and reduce maintenance overhead.

What does the proposed API look like?

import { defineConfig } from '@rslib/core'

export default defineConfig({
  output: {
    exports: true,
  },
})

When enabled, rslib automatically generates exports, main, module, and types fields in package.json based on the build entries.

[Timeless0911]

I've been paying attention to this feature before. I think this is a good way to help library developers reduce their burden when developing simple npm packages, but the limitation is that its accuracy is difficult to guarantee thus we should review the generated fields before publishing. And when users need to modify or override some small parts of generated exports, modifying it through function way seems not direct.

I prefer to introduce this experimental feature through a plugin maybe named rsbuild-plugin-packagejson-exports, e.g. rsbuild-plugin-publint and rsbuild-plugin-arethetypeswrong
.

[Timeless0911]

I prefer to introduce this experimental feature through a plugin maybe named rsbuild-plugin-packagejson-exports, e.g. rsbuild-plugin-publint and rsbuild-plugin-arethetypeswrong.

Considering that this feature should not require additional dependencies, it seems better to have it as a built-in configuration. We will add this feature in the near future, and if you are interested, welcome to contribute a pull request.