Found by a differential test of the packed candidate against the published
2.14.1 across Node 12-22, Bun, TypeScript 4.7-7.0, seven bundlers and a
real browser.
- bowser.mjs is now lowered to ES5 syntax (keeping `export`). Before the
exports map, webpack, Rollup and esbuild resolved `import 'bowser'` to
es5.js via the `browser` field; the ES2015 bowser.mjs broke esbuild
`--target=es5` and shipped classes into webpack ES5 builds. The ESM build
sets `minify: false` explicitly, because rolldown's default DCE-only pass
re-prints the chunk after renderChunk and restores shorthand properties.
- `"sideEffects": ["./bundled.js"]` lets esbuild, Vite and webpack 4 drop an
unused `import 'bowser'`; bundled.js stays listed so polyfill-only imports
are never tree-shaken away.
- `./package` export restores extensionless `require('bowser/package')`,
which resolved on 2.14.1.
- bundled.js imports `core-js/es` plus the timers, immediate and
DOM-collection web polyfills instead of `core-js/stable`, dropping URL,
URLSearchParams and queueMicrotask, which no released bundled.js ever
shipped: 176.9 kB -> 156.1 kB (56.6 -> 49.3 kB gzip).
Tests: bowser.mjs must parse as ES5 apart from its export; bundled.js must
install the @babel/polyfill surface 2.14.1 shipped (passes on 2.14.1's
bundled.js, fails on unpolyfilled es5.js); package smoke test covers
`bowser/package` and `sideEffects`.
