Given an OpenAPI definition, compile into AJV validation modules to be used in environments (like Cloudflare Workers) where eval is not available, or a single JavaScript file is desired.

The normal way:

npm install ajv-openapi-compile --save-dev

You can use the CLI tool, as part of your build process:

ajv-openapi-compile --definition=/path/to/openapi.json \
  --output=/path/to/compiled.js \
  --tree=/path/to/tree.js

You can also use in your build scripts:

import { compile } from 'ajv-openapi-compile'
import { readFile, writeFile } from 'node:fs'
const definition = JSON.parse(await readFile('/path/to/openapi.json', 'utf8'))
const { code, tree } = await compile(definition)
await writeFile('/path/to/compiled.js', code, 'utf8')
await writeFile('/path/to/tree.js', tree, 'utf8')

The output from the compile function contains the code property, which has all imports/requires resolved and concatenated into the single string.

The compiled code is an ES string, and exports schema as the default, which is a map of schema identifiers to validation functions.

If you know the fully-resolved schema id, you can access the validation function explicitly:

import schemas from '/path/to/compiled.js'
const validate = schemas['#/components/schema/error']
const valid = validate({ code: 404 })
if (!valid) console.log(validate.errors)

Note: The schema identifiers are escaped using the JSON Pointer (RFC6901) specs, which turns ~ into ~0 and / into ~1.

If you don't know the fully-resolved schema id, you can use something like pointer-props to navigate the structure and resolve to the correct id:

import { resolve, toPointer } from 'pointer-props'
import { readFile } from 'node:fs'
import schemas from '/path/to/compiled.js'
const definition = JSON.parse(await readFile('/path/to/openapi.json', 'utf8'))
// lookup the id
const id = resolve(definition, '#/path/to/schema') // => '/path/to/fully/resolved/schema'
// note the relative reference requires "#" as the prefix
const validate = schemas['#' + id]
const valid = validate({ code: 404 })
if (!valid) console.log(validate.errors)

The CLI takes the following parameters:

• ---definition, -d (String) - The path to the definition JSON file.
• ---output, -o (String) - The path to write the compiled AJV validation code.

For convenience and compatability with other tooling, the definition parameter also supports importing JavaScript files, and will follow this algorithm:

1. If the file extension is .json read and parse as JSON
2. If the file extension is .yaml or .yml read and parse as YAML (using js-yaml internally)
3. Otherwise, attempt importing * as schema
4. If schema.definition is set, use that
5. Otherwise, try using schema
6. Otherwise, try importing the default as schema and try that

To be considered valid, the imported schema definition must have a paths object, with at least one "Path Object" defined.

The function simply takes a valid OpenAPI 3.x object.

It returns an object with the following properties:

• code: String - The compiled code, with all import and require statements resolved and placed inline.

Published and released under the Very Open License.

If you need a commercial license, contact me here.