[Feature]: expose stats result for `build` command by js api

[XGHeaven]

What problem does this feature solve?

Rsilb has build js api. But cannot get compiled stats object for returned instance after first compiled.
I tried onAfterBuild hook is still not works.

import { build } from '@rslib/core'

const instance = await build(/*..., config and options*/)

instance.stats // undefined
instance.onAfterBuild(options => {
  // not called when first compiled
})

What does the proposed API look like?

instance.stats // is a object
// or
instance.onAfterBuild(options => {
  // should called when first compiled
})

It's better to expose stats for buildInstance or allow developer to register hook before run rsbuildInstance.build.

[Timeless0911]

This should be an unexpected bug that the Rsilb JS API does not return the real Rsbuild's build returns.

Before releasing 1.0, I want to design JS API further to add a createRslib api to return the Rsbuild instance thus user can modify this instance as same as Rsbuild which will bring a breaking change for Rslib JS API. And stats will be exposed naturally.

[Timeless0911]

In order to minimize breaking changes before the final design is determined, this feature may not be implemented immediately.

You can use the following way to get stats as a workaround now.

import { build, rsbuild } from "@rslib/core";

const statsPlugin: rsbuild.RsbuildPlugin = {
  name: "get-stats",
  setup(api) {
    api.onAfterBuild(({ stats }) => {
      console.log(stats?.toJson({}));
    });
  },
};

await build({
  lib: [
    {
      format: "esm",
      // ...
    },
  ],
  plugins: [statsPlugin],
});