Fix tsup configuration for vanilla Webpack 4 without babel-loader

[compulim]

Changelog Entry

Fixed

• Improved importability in vanilla Webpack 4 without babel-loader, by @compulim, in PR #5322

Description

There are some limitations on vanilla Webpack 4 without babel-loader:

• Cannot load ESM and it imports CJS (a.k.a. "ESM -> CJS")
  • We need noExternal: 'globalize' only for ESM
    • globalize is CJS-only, we bundle it inside Web Chat so it don't do "ESM -> CJS"
  • We don't need bundling for CJS as it won't do "ESM -> CJS"
• Webpack 4 does not understand ES2020, need to target ES2019
  • It does not understand ?? operator
• No named imports, requires barrel file for interoperability
  • We made some mistakes in our barrel file
  • Barrel files need to point to .js, otherwise, Webpack 4 may point to .mjs which will require Babel

Also, in tsup, it disabled code splitting for CJS as esbuild does not support it. We are using experimental flag to re-enable it.

If you want code splitting for cjs output format as well, try using --splitting flag which is an experimental feature to get rid of the limitation in esbuild.

Design

Specific Changes

• Fix barrel files and force it to CJS
• Target ES2019 for CJS, Chrome 100/Safari 15 for ESM
• Bundle globalize only in ESM but not CJS
  • Only needed in ESM as globalize is CJS only and it would cross the ESM -> CJS boundary
• Force code splitting for CJS
  • We have multiple entrypoints: botframework-webchat-[api|component]/[decorator|internal]
  • React context requires same instance, i.e. code splitting is required

• I have added tests and executed them locally
• I have updated CHANGELOG.md
• I have updated documentation

Review Checklist

This section is for contributors to review your work.

• Accessibility reviewed (tab order, content readability, alt text, color contrast)
• Browser and platform compatibilities reviewed
• CSS styles reviewed (minimal rules, no z-index)
• Documents reviewed (docs, samples, live demo)
• Internationalization reviewed (strings, unit formatting)
• package.json and package-lock.json reviewed
• Security reviewed (no data URIs, check for nonce leak)
• Tests reviewed (coverage, legitimacy)

[OEvgeny]

Looks good. Who the hell is using Webpack 4 without any preloader in 2024? It kind of kills progress of the past ~4 years in web development.