feat: add first-class Rsbuild adapter

[yslpn]

Describe the feature

unplugin@3.0.0 provides first-class adapters for Vite, Webpack, Rollup, esbuild, and Rspack, but it does not currently expose a first-class Rsbuild adapter.

Specifically, there is no:

• createRsbuildPlugin(factory)
• createUnplugin(factory).rsbuild

Rsbuild is built on top of Rspack, so many unplugin-based transforms can work in an Rsbuild project through a manual Rspack configuration workaround. However, package authors cannot expose a clean my-plugin/rsbuild entrypoint with the same ergonomics as existing adapters.

Motivation

Rsbuild users currently need to wire unplugin-based Rspack plugins through tools.rspack, which is less discoverable and less consistent than the existing adapter model.

For plugin authors, this also means packages can expose:

• my-plugin/vite
• my-plugin/webpack
• my-plugin/rollup
• my-plugin/esbuild
• my-plugin/rspack

but not a native:

• my-plugin/rsbuild

A first-class Rsbuild adapter would make Rsbuild support consistent with the rest of the supported build tools.

Proposed API

import {createRsbuildPlugin} from 'unplugin'
import {unpluginFactory} from './index.js'

export default createRsbuildPlugin(unpluginFactory)

And through createUnplugin:

import {createUnplugin} from 'unplugin'

const plugin = createUnplugin(factory)

export default plugin.rsbuild

Expected Usage

// rsbuild.config.ts
import {defineConfig} from '@rsbuild/core'
import myPlugin from 'my-plugin/rsbuild'

export default defineConfig({
  plugins: [
    myPlugin({
      /* plugin options */
    }),
  ],
})

Current Workaround

Today, Rsbuild users can often route the Rspack adapter manually through tools.rspack:

// rsbuild.config.ts
import {defineConfig} from '@rsbuild/core'
import myPlugin from 'my-plugin/rspack'

export default defineConfig({
  tools: {
    rspack(config) {
      config.plugins ??= []
      config.plugins.push(myPlugin())
    },
  },
})

This works for some plugins, but it is not as ergonomic or discoverable as a native Rsbuild plugin. It also requires users to know that Rsbuild is Rspack-based and that the Rspack adapter can be manually inserted into the generated Rspack config.

Additional information

• Would you be willing to help implement this feature?