Add Dual Support for ESM and CommonJS in Flossum

[pushkarscripts]

Problem Description:

Currently, the package is configured as "type": "module" in package.json, which makes it ESM-only. This causes issues when other developers or tools try to require('flossum') in a CommonJS environment, resulting in the error:

❌ The package doesn't seem to have a CommonJS entry point

Goal: Update flossum to support both CommonJS (require) and ESM (import) so it can be used in any environment.

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Proposed Directory Structure:

flossum/
├── src/
│   └── index.js         # Source code (ESM)
├── dist/
│   ├── index.mjs        # Output ESM build
│   └── index.cjs        # Output CJS build
├── package.json

package.json Changes:

{
  "type": "module",
  "main": "./dist/index.cjs",
  "module": "./dist/index.mjs",
  "exports": {
    "require": "./dist/index.cjs",
    "import": "./dist/index.mjs"
  },
  "bin": {
    "flossum": "./dist/index.mjs"
  },
  "scripts": {
    "build": "node build.mjs"
  }
}

Build Setup:

Use esbuild to generate both ESM and CJS builds:

npx esbuild src/index.js --bundle --platform=node --format=esm --outfile=dist/index.mjs
npx esbuild src/index.js --bundle --platform=node --format=cjs --outfile=dist/index.cjs

Optional: Automate with a build.mjs script or directly in package.json.

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Resulting Usage:

✅ import { fn } from 'flossum' — works in ESM
✅ const { fn } = require('flossum') — works in CommonJS
✅ CLI remains intact

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Test Checklist:

• npm pack works without warning
• require('flossum') in CJS project works
• import in ESM project works
• CLI (flossum) functions the same
• npm publish --dry-run is clean

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Note:

• No need to change "type": "module" — just generate a .cjs file as fallback.
• Avoid index.js ambiguity — always use .mjs and .cjs for clarity in dual support.
• This setup ensures compatibility with Node.js, bundlers, and all modern tooling.