t12n — typevalidation

Type-driven runtime validation for TypeScript. A tiny build plugin (Vite, webpack, Rollup, esbuild, Rspack) that turns your TypeScript types into runtime validators: annotate the data that crosses a boundary, and the schemas, checks and errors write themselves.

const user: User = await fetch('/api/me').then(r => r.json())
// the plugin inserts the runtime check — a bad payload throws right here

Repository layout

This is a pnpm workspace (packages/* + site).

Develop

pnpm install
pnpm -r build                  # build all packages (t12n + site)
pnpm -r test                   # run tests
pnpm --filter t12n dev         # build the package in watch mode
pnpm --filter @t12n/site dev   # run the site locally

Publishing

• Package → npm: cd packages/t12n && npm publish (only dist ships, per the package's files field — not the whole monorepo).
• Site → Vercel: configured by the root vercel.json — build pnpm --filter @t12n/site build, output site/dist. The site build compiles the t12n package first, then runs astro build and the Pagefind search index.

License

MIT