Tree shaking not working with RollupJS

Prerequisites

• I have searched for duplicate or closed issues
• I have validated any HTML to avoid common problems
• I have read the contributing guidelines

Describe the issue

I can't make tree shaking working using Bootstrap. If I try something like

import { Button } from 'bootstrap'

I get the whole library included in my bundle.

Reduced test cases

The Rollup.js configuration I'm using is the following:

// rollup.config.js

import { babel } from '@rollup/plugin-babel'
import scss from 'rollup-plugin-scss'
import uglify from '@lopatnov/rollup-plugin-uglify'
import nodeResolve from '@rollup/plugin-node-resolve'
import commonjs from '@rollup/plugin-commonjs'
import injectProcessEnv from 'rollup-plugin-inject-process-env'


export default [
  {
    input: 'demo.entry.js',
    output: {
      file: 'dist/js/demo.bundle.min.js',
      format: 'iife',
      compact: true
    },
    plugins: [
      babel({
        babelHelpers: 'bundled',
        exclude: 'node_modules/**',
      }),
      scss({
        output: 'dist/css/demo.min.css',
        outputStyle: 'compressed',
        sourceMap: true,
      }),
      nodeResolve(),
      commonjs(),
      injectProcessEnv({
        NODE_ENV: 'production',
      }),
      uglify()
    ],
  }
]

What operating system(s) are you seeing the problem on?

macOS

What browser(s) are you seeing the problem on?

Chrome

What version of Bootstrap are you using?

v5.1.3

Start with the reported rollup.config.js and demo.entry.js, then reproduce the Bootstrap v5.1.3 build using the listed Rollup plugins. Inspect the generated bundle to confirm whether importing Button includes the whole library. Done means the reduced example produces a bundle containing only the required Bootstrap code, with the existing build configuration or a documented limitation clarified.