ts-packaging

TypeScript Packaging

Ship a TypeScript library with a correct exports map, on the right registry.

Agent Workflow (MANDATORY)

Before ANY implementation, use TeamCreate to spawn 3 agents:

1. fuse-ai-pilot:explore-codebase - Inspect package.json, build output, targets
2. fuse-ai-pilot:research-expert - Verify latest JSR / npm / Node exports docs via Context7/Exa
3. mcp__context7__query-docs - Check conditions ordering, attw usage

After implementation, run fuse-ai-pilot:sniper for validation.

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Overview

Registry	Format	Publishes	Best for
JSR	ESM only	TS source directly	Deno/Node/Bun libs, doc-rich APIs
npm	ESM (or dual ESM/CJS)	Built .js + .d.ts	Broadest public reach, CJS consumers

Rule of thumb: internal or Bun/Deno/ESM-only consumer → ESM-pure; broad public library still serving CommonJS → dual ESM/CJS.

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Critical Rules

1. "types" first, "default" last - Conditions match in object order
2. Match import↔ESM and require↔CJS - Never point require at ESM
3. One subpath per module - Consistent specifier; set "type": "module" explicitly
4. Validate with attw - arethetypeswrong before every publish
5. Provenance on public releases - Publish from CI with id-token: write

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Decision Guide

Publishing a TS library?
├── Consumers on Deno/Bun/Node ESM, want source + docs → JSR (ESM only)
│   └── Fix "slow types" (explicit return/prop/const types)
└── Public npm audience
    ├── ESM-only consumers → ESM-pure package.json
    └── Some consumers still on CJS → dual ESM/CJS exports

→ See references/exports-map.md for the conditions model

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Reference Guide

Concepts

Topic	Reference	Load when
Exports map & conditions	references/exports-map.md	Writing the exports field
JSR publishing	references/jsr-publishing.md	Publishing TS source to JSR
npm publishing	references/npm-publishing.md	Publishing to npm (dual/ESM)
Type validation	references/validation.md	Checking types resolve correctly

Templates

Template	Use Case
references/templates/package-json-dual.md	Dual ESM/CJS + ESM-pure package.json
references/templates/jsr-json.md	jsr.json with multi-entry exports
references/templates/publish-workflow.md	GitHub Actions release with provenance

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Quick Start

Modern exports (ESM-pure)

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

Validate before publish

npx @arethetypeswrong/cli --pack

→ See references/validation.md

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Best Practices

DO

• Set "type" explicitly, even for CJS packages
• Provide types in every conditional branch
• Publish from CI so provenance is automatic

DON'T

• Ship dual CJS when every consumer is ESM (dead weight)
• Order "default" before "types" (breaks type resolution)
• Use --allow-slow-types on JSR as a habit (degrades docs + npm compat)