/dx-audit

Ship Tree-Shakeable ESM with an Accurate sideEffects Flag

A CommonJS-only bundle, or a package with sideEffects unset (bundlers then assume true), makes every consumer ship the whole library for one import. Ship ESM, set "sideEffects": false or the exact list of files that do run code on import (a polyfill, a CSS import), and put heavy optional features behind subpath exports so import "pkg/charts" costs nothing to the consumer who never uses it. Whether each entry then resolves and is typed is onboard-exports-resolve-typed.

Incorrect (CJS-only, no exports map, sideEffects unset so it defaults to true):

{
  "main": "dist/index.js"
  // no "type", no "exports", no "sideEffects": importing one helper
  // pulls the entire bundle into the consumer's build
}

Correct (ESM, tree-shaking enabled, heavy feature behind a subpath):

{
  "type": "module",
  "sideEffects": false,
  "exports": {
    ".": { "types": "./dist/index.d.ts", "default": "./dist/index.js" },
    "./charts": { "types": "./dist/charts.d.ts", "default": "./dist/charts.js" }
  }
}