Scalar OpenAPI Parser

Modern OpenAPI parser written in TypeScript with support for OpenAPI 3.1, OpenAPI 3.0 and Swagger 2.0.

Goals

• [x] Written in TypeScript
• [x] Runs in Node.js and in the browser (without any polyfills or configuration)
• [x] Tested with hundreds of real world examples
• [ ] Amazing error output
• [ ] Support for OpenAPI 4.0 👀

Installation

npm add @scalar/openapi-parser

Usage

Validate

import { validate } from '@scalar/openapi-parser'

const file = `{
  "openapi": "3.1.0",
  "info": {
    "title": "Hello World",
    "version": "1.0.0"
  },
  "paths": {}
}`

const { valid, errors } = await validate(file)

console.log(valid)

if (!valid) {
  console.log(errors)
}

Resolve references

import { dereference } from '@scalar/openapi-parser'

const specification = `{
  "openapi": "3.1.0",
  "info": {
    "title": "Hello World",
    "version": "1.0.0"
  },
  "paths": {}
}`

const { schema, errors } = await dereference(specification)

Track references

The dereference function accepts an onDereference callback option that gets called whenever a reference is resolved. This can be useful for tracking which schemas are being dereferenced:

import { dereference } from '@scalar/openapi-parser'

const { schema, errors } = await dereference(specification, {
  onDereference: ({ schema, ref }) => {
    //
  },
})

Modify an OpenAPI document

import { filter } from '@scalar/openapi-parser'

const specification = `{
  "openapi": "3.1.0",
  "info": {
    "title": "Hello World",
    "version": "1.0.0"
  },
  "paths": {}
}`

const { specification } = filter(specification, (schema) => !schema?.['x-internal'])

Upgrade your OpenAPI document

There’s an upgrade command to upgrade all your OpenAPI documents to the latest OpenAPI version.

⚠️ The upgrade from Swagger 2.0 is still experimental and probably lacks features.

import { upgrade } from '@scalar/openapi-parser'

const { specification } = upgrade({
  swagger: '2.0',
  info: {
    title: 'Hello World',
    version: '1.0.0',
  },
  paths: {},
})

console.log(specification.openapi)
// Output: 3.1.0

Sanitize your OpenAPI document

The sanitize() utility helps ensure your OpenAPI document is valid and complete. It automatically adds any missing required properties like the OpenAPI version and info object, collects operation tags and adds them to the global tags array and normalizes security scheme types.

This makes your document as OpenAPI-compliant as possible with minimal effort, handling many common specification requirements automatically.

⚠️ This doesn’t support Swagger 2.0 documents.

import { sanitize } from '@scalar/openapi-parser'

const result = sanitize({
  info: {
    title: 'Hello World',
  },
})

console.log(result)

Pipeline syntax

import { openapi } from '@scalar/openapi-parser'

const specification = …

// New pipeline …
const result = openapi()
  // loads the specification …
  .load(specification)
  // upgrades to OpenAPI 3.1 …
  .upgrade()
  // removes all internal operations …
  .filter((schema) => !schema?.['x-internal'])
  // done!
  .get()

Then/Catch syntax

If you’re more the then/catch type of guy, that’s fine:

import { validate } from '@scalar/openapi-parser'

const specification = …

validate(specification, {
  throwOnError: true,
})
.then(result => {
  // Success
})
.catch(error => {
  // Failure
})

TypeScript

If you just look for our types, you can install the package separately:

npm add @scalar/openapi-types

And use it like this:

import type { OpenAPI } from '@scalar/openapi-types'

const file: OpenAPI.Document = {
  openapi: '3.1.0',
  info: {
    title: 'Hello World',
    version: '1.0.0',
  },
  paths: {},
}

Advanced: URL and file references

You can reference other files, too. To do that, the parser needs to know what files are available.

import { dereference, load } from '@scalar/openapi-parser'
import { fetchUrls } from '@scalar/openapi-parser/plugins/fetch-urls'
import { readFiles } from '@scalar/openapi-parser/plugins/read-files'

// Load a file and all referenced files
const { filesystem } = await load('./openapi.yaml', {
  plugins: [
    readFiles(),
    fetchUrls({
      limit: 5,
    }),
  ],
})

// Instead of just passing a single specification, pass the whole “filesystem”
const result = await dereference(filesystem)

As you see, load() supports plugins. You can write your own plugin, if you’d like to fetch API defintions from another data source, for example your database. Look at the source code of the readFiles to learn how this could look like.

Directly load URLs

Once the fetchUrls plugin is loaded, you can also just pass an URL:

import { dereference, load } from '@scalar/openapi-parser'
import { fetchUrls } from '@scalar/openapi-parser/plugins/fetch-urls'

// Load a file and all referenced files
const { filesystem } = await load(
  'https://cdn.jsdelivr.net/npm/@scalar/galaxy/dist/latest.yaml',
  {
    plugins: [fetchUrls()],
  },
)

Intercept HTTP requests

If you’re using the package in a browser environment, you may run into CORS issues when fetching from URLs. You can intercept the requests, for example to use a proxy, though:

import { dereference, load } from '@scalar/openapi-parser'
import { fetchUrls } from '@scalar/openapi-parser/plugins/fetch-urls'

// Load a file and all referenced files
const { filesystem } = await load(
  'https://cdn.jsdelivr.net/npm/@scalar/galaxy/dist/latest.yaml',
  {
    plugins: [
      fetchUrls({
        fetch: (url) => fetch(url.replace('BANANA.net', 'jsdelivr.net')),
      }).get('https://cdn.BANANA.net/npm/@scalar/galaxy/dist/latest.yaml'),
    ],
  },
)

Community

We are API nerds. You too? Let’s chat on Discord: https://discord.gg/scalar

Thank you!

Thanks a ton for all the help and inspiration:

• @philsturgeon to make sure we build something we won’t hate.
• We took a lot of inspiration from @seriousme and his package openapi-schema-validator early-on.
• You could consider this package the modern successor of @apidevtools/swagger-parser, we even test against it to make sure we’re getting the same results (where intended).
• We stole a lot of example specification from @mermade to test against.

License

The source code in this repository is licensed under MIT.