@ata-project/unplugin

Compiles JSON Schema files into self-contained ata-validator modules at build time, with TypeScript declarations, in Vite, Webpack, Rollup, Rolldown, esbuild and Rspack. One plugin, built on unplugin.

The generated module imports nothing. A typical schema compiles to about 1 KB gzipped, exports validate, isValid and the inferred type, and runs anywhere plain JavaScript runs.

Schemas can be authored as .json, .js or .ts.

npm install --save-dev @ata-project/unplugin ata-validator

ata-validator is a peer dependency and is only used at build time.

Vite:

// vite.config.ts
import ata from '@ata-project/unplugin/vite'

export default {
  plugins: [ata({ schemas: 'src/**/*.schema.json' })],
}

Webpack:

// webpack.config.js
const ata = require('@ata-project/unplugin/webpack')

module.exports = {
  plugins: [ata({ schemas: 'src/**/*.schema.json' })],
}

Rollup:

// rollup.config.js
import ata from '@ata-project/unplugin/rollup'

export default {
  // Rollup has no project root; tell the plugin where the globs start.
  plugins: [ata({ schemas: 'src/**/*.schema.json', root: process.cwd() })],
}

esbuild:

import { build } from 'esbuild'
import ata from '@ata-project/unplugin/esbuild'

await build({
  entryPoints: ['src/main.ts'],
  bundle: true,
  plugins: [ata({ schemas: 'src/**/*.schema.json' })],
})

Rspack:

// rspack.config.js
const ata = require('@ata-project/unplugin/rspack')

module.exports = {
  plugins: [ata({ schemas: 'src/**/*.schema.json' })],
}

Rolldown:

// rolldown.config.js
import ata from '@ata-project/unplugin/rolldown'

export default {
  plugins: [ata({ schemas: 'src/**/*.schema.json', root: process.cwd() })],
}

Next.js uses Webpack, so the Webpack entry goes into next.config.js:

const ata = require('@ata-project/unplugin/webpack')

module.exports = {
  webpack(config) {
    config.plugins.push(ata({ schemas: 'schemas/**/*.schema.json' }))
    return config
  },
}

Turbopack has no plugin interface this could attach to. Run the compile as a step before the build instead: ata build 'schemas/**/*.schema.json' from ata-validator's CLI, or the compile() function below in a script.

Name a schema user.schema.json and import a typed validator by its name:

import validate, { type User, isValid } from './user.schema'

const r = validate(input)
if (r.valid) {
  // input matched the schema
}
if (isValid(input)) {
  input.id // narrowed to User
}

The plugin writes user.schema.js and user.schema.d.ts next to the schema. The default export is the validate function; validate, isValid and the inferred type are also named exports. The type name comes from the schema's title, then its $id, then the file name.

Add the generated files to .gitignore:

*.schema.js
*.schema.d.ts

Other sources (.json without the .schema suffix, .js, .ts) produce <name>.validator.mjs and <name>.validator.d.mts.

Output goes to disk, not to virtual modules. That is what makes the plugin identical across bundlers and what lets TypeScript see the generated declarations without any bundler-specific type plumbing.

Schemas compile on build start. On a schema change, Vite recompiles through its HMR hook and Webpack, Rspack, Rollup and Rolldown through watchChange. esbuild has no watch hook, so under esbuild --watch a schema edit alone does not trigger a rebuild; the next build start compiles it.

.ts schemas load through jiti. A schema module exports the schema as default or as a named schema.

A schema the standalone compiler cannot represent is reported with a warning and skipped; the ata-validator runtime API still validates it.

import { compile } from '@ata-project/unplugin'

const { files, results } = await compile({ schemas: 'schemas/**/*.json', root: process.cwd() })

npm test compiles the same entry with Vite, Webpack, Rollup, Rolldown, esbuild and Rspack, imports each bundle and runs the validator it contains.

The package is @ata-project/unplugin; the plugin registers itself in the bundler as unplugin-ata, which is the name in log lines and in plugin.name. The unscoped name is not available on npm.

ata-vite is this plugin's Vite entry with the old name. It keeps working; new projects can use either.

MIT