ata-vite

Vite plugin that compiles JSON Schema files into self-contained ata-validator modules plus TypeScript declarations. Build time instead of runtime, ~1 KB gzipped per schema, full type narrowing via isValid.

Install

npm install --save-dev ata-vite ata-validator

ata-validator is a peer dependency.

Quick start

// vite.config.ts
import { defineConfig } from 'vite'
import ata from 'ata-vite'

export default defineConfig({
  plugins: [
    ata({
      schemas: 'schemas/**/*.json',
      // outDir: 'src/generated',  // optional; defaults to next to each input
    }),
  ],
})

For every matched <name>.json the plugin writes:

• <name>.validator.mjs - self-contained validator, no runtime dependency on ata-validator
• <name>.validator.d.mts - TypeScript declaration with an isValid type predicate

Import from your app:

import { isValid, validate, type User } from './schemas/user.validator.mjs'

export function handle(input: unknown) {
  if (isValid(input)) {
    // TypeScript narrows `input` to User here
    return { ok: true, id: input.id, role: input.role }
  }
  return { ok: false, errors: validate(input).valid ? [] : validate(input).errors }
}

Options

ata({
  schemas: 'schemas/**/*.json',  // glob or array of globs, relative to Vite root
  outDir: null,                  // null = alongside each input; or a folder like 'src/generated'
  format: 'esm',                 // 'esm' | 'cjs'
  abortEarly: false,             // true = stub errors, smallest output
  types: true,                   // false to skip .d.mts / .d.cts
  nameFromFile: (file) => string // customize the TS type name derived from filename
})

abortEarly

Replaces the detailed error collector in the generated validator with a shared stub. Output drops from roughly 1.2 KB gzipped to 0.6 KB gzipped on a typical 10-field schema. Use it when the caller only needs a boolean reject/accept decision.

outDir

By default the output lands next to each input file. Pass a directory to relocate everything to <outDir>/<mirrored input path>/<base>.validator.*. Easier to .gitignore when you do not want generated files checked in.

Idempotent writes

If the generated content matches what is already on disk, the file is not rewritten. TypeScript watch and Vite HMR stay quiet during no-op rebuilds.

Programmatic API

Useful in custom build scripts outside Vite.

import { compile } from 'ata-vite'

await compile({
  schemas: 'schemas/**/*.json',
  outDir: 'src/generated',
  abortEarly: true,
  root: process.cwd(),
})

Returns { files, results } where results[i].changed indicates whether the output file was actually rewritten.

What it does under the hood

Each matched schema is compiled via new Validator(schema).toStandaloneModule(...) and toTypeScript(schema, { name }) from ata-validator. No subprocess, no CLI wrapper. The plugin hooks:

• configResolved - resolve Vite root and logger
• buildStart - compile every matched schema
• handleHotUpdate - recompile on file change in dev mode
• watchChange - same, for rollup-style watch contexts outside a dev server

License

MIT