swagger-routes-express

Connect Express route controllers to restful paths using a Swagger v2 or OpenAPI v3 definition file.

Assumptions

This library assumes you are using:

1. NodeJS version 6.4.0 or better,
2. expressjs any version, and
3. swagger version 2, or OpenAPI version 3.

Install

Add swagger-routes-express as a dependency:

npm i swagger-routes-express

Examples

A simple API

Assume the following API route controllers, defined in ./api/index.js as follows:

const { name, version, description } = require('../../package.json')

const versions = (req, res) => {
  res.json([
    {
      version: 1,
      path: '/api/v1'
    }
  ])
}

const ping = (req, res) => {
  res.json({
    name,
    description,
    version,
    uptime: process.uptime()
  })
}

module.exports = { ping, versions }

Swagger Version 2 example

Given a Swagger (v2) YAML file api.yml along the lines of:

swagger: '2.0'
info:
  description: Something about the API
  version: '1.0.0'
  title: 'Test API'
basePath: '/api/v1'
schemes:
  - 'https'
  - 'http'
paths:
  /:
    get:
      tags:
        - 'root'
      summary: 'Get API Version Information'
      description: 'Returns a list of the available API versions'
      operationId: 'versions'
      produces:
        - 'application/json'
      responses:
        200:
          description: 'success'
          schema:
            $ref: '#/definitions/ArrayOfVersions'
  /ping:
    get:
      tags:
        - 'root'
      summary: 'Get Server Information'
      description: 'Returns information about the server'
      operationId: 'ping'
      produces:
        - 'application/json'
      responses:
        200:
          description: 'success'
          schema:
            $ref: '#/definitions/ServerInfo'
definitions:
  # see https://swagger.io/docs/specification/data-models/data-types
  APIVersion:
    type: 'object'
    properties:
      version:
        type: 'integer'
        format: 'int64'
      path:
        type: 'string'
  ServerInfo:
    type: 'object'
    properties:
      name:
        type: 'string'
      description:
        type: 'string'
      version:
        type: 'string'
      uptime:
        type: 'number'
  ArrayOfVersions:
    type: 'array'
    items:
      $ref: '#/definitions/APIVersion'

OpenAPI Version 3 example

openapi: 3.0.0
info:
  description: Something about the API
  version: 1.0.0
  title: Test API
paths:
  /:
    get:
      tags:
        - root
      summary: Get API Version Information
      description: Returns a list of the available API versions
      operationId: versions
      responses:
        '200':
          description: success
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ArrayOfVersions'
  /ping:
    get:
      tags:
        - root
      summary: Get Server Information
      description: Returns information about the server
      operationId: ping
      responses:
        '200':
          description: success
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ServerInfo'
servers:
  - url: /api/v1
components:
  schemas:
    APIVersion:
      type: object
      properties:
        version:
          type: integer
          format: int64
        path:
          type: string
    ServerInfo:
      type: object
      properties:
        name:
          type: string
        description:
          type: string
        version:
          type: string
        uptime:
          type: number
    ArrayOfVersions:
      type: array
      items:
        $ref: '#/components/schemas/APIVersion'

Connecting your Express server

You can connect your Express app or router as follows:

const express = require('express')
const YAML = require('yamljs')
const { connector } = require('swagger-routes-express')
const api = require('./api')

const makeApp = () => {
  const apiDefinition = YAML.load('api.yml') // load the api as json
  const connect = connector(api, apiDefinition) // make the connector
  const app = express() // make the app

  // do any other app stuff, such as wire in passport, use cors etc

  connect(app) // attach the routes

  // add any error handlers last

  return app
}

With the result that requests to GET / will invoke the versions controller and a request to /ping will invoke the ping controller.

Options

You can pass in an optional options object as a third parameter to the connector function.

const connect = connector(api, apiDefinition, options)

If you don't pass in any options the defaults are:

{
  security: {},
  middleware: {},
  onCreateRoute: undefined,
  apiSeparator: '_',
  notFound: : require('./routes/notFound'),
  notImplemented: require('./routes/notImplemented'),
  rootTag: 'root', // only used in Swagger V2 docs
  variables: {}, // only used in OpenAPI v3 docs
  INVALID_VERSION: require('./errors').INVALID_VERSION
}

Adding security middleware handlers

There are several ways to add middleware handlers, and they can be combined to provide a high degree of customisation and flexibility.

Specify Auth middleware by name in the API definition yml file

If your swagger document defines security, you can map this to your own Auth Middleware by passing in a security option to the connector.

Security with scopes

For example if your path defines oAuth style security like:

paths:
  /private
    get:
      summary: some private route
      security:
        - access: ['read', 'write']
  /admin
    get:
      summary: some admin route
      security:
        - access: ['admin']

Supply a security option as follows

const options = {
  security: {
    'read,write': readWriteAuthMiddlewareFunction,
    admin: adminAuthMiddlewareFunction
  }
}

Security without scopes

If your path defines security, and its scopes array is empty, you use its name in the security option.

Given:

paths:
  /private
    get:
      summary: some private route
      security:
        - apiKey: []

Supply a security option like:

const options = {
  security: {
    apiKey: myAuthMiddlewareFunction
  }
}

Return an array of controllers

Your API might wish to leverage some middleware functions but you don't want to have to specify them all in the API document itself.

Your API controller functions themselves can return arrays of controller functions.

Example

In this case /api/v1/createThings/index.js returns an array of controller functions with bespoke middleware controllers running in sequence, and then runs the controller in /api/v1/createThings/createThings.js

/api/v1/createThings/index.js

const { checkIfAllowed, stripPII } = require('middleware')
const actuallyCreateThings = require('./createThings')

const createThings = [checkIfAllowed, stripPII, actuallyCreateThings]

The array of middleware and your controller will be executed in order, so it's important to put your actual controller logic last.

Global security definitions

Both Swagger V2 and OpenAPI V3 allow you to define global security. The global security definition will be applied if there is no path-specific one defined.

Exempting a path from global security

If you've defined global security but wish to exempt a specific path, then you can configure the path like:

paths:
  /my-route
    get:
      summary: some route that is exempt from the default security
      security: []

Further reading on Swagger and security

• Swagger V2 Authentication, and
• Open API V3 Authentication docs.

Notes

• Only the first security option is used, the others are ignored. Your Auth Middleware function must handle any alternative authentication schemes. This can be achieved by returning an array of middleware controllers that culminates in the specific api controller you want.
• Security middleware, wither defined at the global or path level, is applied first, then any controller specific arrays of middleware are applied,
• Scopes, if supplied, are sorted alphabetically.

What's an Auth Middleware function?

An Auth Middleware Function is simply an Express Middleware function that checks to see if the user making the request is allowed to do so.

How this actually works in your server's case is going to be completely application specific, but the general idea is your app needs to be able to log users in, or accept a token from a header, or somehow otherwise stick a user id, or some roles, into req.user or req.session.user or something like that. There are dozens of ways to do this. I recommend using something like Passport to handle the specifics.

Your Auth Middleware then just needs to check that the user / roles you've stored corresponds with what you'd like to allow that user to do.

async function correspondingMiddlewareFunction(req, res, next) {
  // previously you have added a userId to req (say from an 'Authorization: Bearer token' header)
  // how you check that the token is valid is up to your app's logic
  if (await isValidToken(req.user.token)) return next()

  // otherwise reject with an error
  return res.status(401).json({ error: "I'm afraid you can't do that" })
}

• More information… (via DuckDuckGo)

Adding other path-level middleware

You can add your own path specific middleware by passing in a middleware option:

{
  middleware: {
    myMiddleware: someMiddlewareFunction
  }
}

With either Swagger v2 or OpenAPI v3, add an x-middleware option in the path specification:

paths:
  /special:
    get:
      summary: some special route
      x-middleware:
        - myMiddleware

The someMiddlewareFunction will be inserted after any Auth Middleware.

Adding hooks

You can supply an onCreateRoute handler function with the options with signature

const onCreateRoute = (method, descriptor) => {
  const [path, ...handlers] = descriptor
  console.log('created route', method, path, handlers)
}

The method will be one of 'get', 'post', 'patch', 'put', or 'delete'.

The descriptor is an array of:

;[
  path, // a string. Swagger param formats will have been converted to express route formats.
  security, // an auth middleware function (if needed)
  ...middleware, // other middleware functions (if supplied)
  controller //  then finally the route controller function
]

Mapping to nested API routes

If your ./api folder contains nested controllers such as:

/api/v1/createThing.js

It's not uncommon for ./index.js to expose this as v1_createThing, but in swagger the operationId might specify it as v1/createThing.

You can supply your own apiSeparator option in place of _ to map from /.

Arrays of route controllers

In this case /api/v1/createThings.js returns an array of controller functions with bespoke middleware controllers running in sequence. This is a shortcut for otherwise specifying middleware as outlined above.

Missing Route Controllers

If a route controller is defined as an operationId in Swagger but there is no corresponding controller, a default notImplemented controller will be inserted that simply responds with a 501 error. You can also specify your own notImplemented controller in options.

If no operationId is supplied for a path then a default notFound controller that responds with a 404 status will be inserted. You can also specify your own notFound controller in options.

Base paths

Swagger Version 2

For the root path / we check the route's tags. If the first tag defined for a path is 'root' we don't inject the api basePath, otherwise we do. You can define your own rootTag option to override this behaviour.

OpenAPI Version 3

The OpenAPI V3 format allows you to define both a default servers array, and path specific servers arrays. The url fields in those arrays are parsed, ignoring any absolute URLS (as they are deemed to refer to controllers external to this API Server).

The spec allows you to include template variables in the servers' url field. To accommodate this you can supply a variables option in options. Any variables you specify will be substituted.

Generating API summary information

You can generate a summary of your Swagger v2 or OpenAPI v3 API specification in the form:

{
  info: { name, version, description },
  paths: { [method]: ['/array', '/of', '/normalised/:paths'] }
}

as follows:

const YAML = require('yamljs')
const { summarise } = require('swagger-routes-express')

const apiDefinition = YAML.load('api.yml')
const apiSummary = summarise(apiDefinition)

Upgrading from Swagger Routes Express V2 to V3

These docs refer to Version 3 of Swagger Routes Express which changed the way you invoke the connector.

The old way

const connector = require('swagger-routes-express')

The new way

const { connector } = require('swagger-routes-express')

Development

Branches

Branch	Status	Coverage	Audit	Notes
develop				Work in progress
main				Latest stable release

Prerequisites

• NodeJS. I use nvm to manage Node versions — brew install nvm.

Test it

• npm test — runs the unit tests.
• npm run test:unit:cov - run the unit tests with coverage.

Lint it

npm run lint

Starter templates and examples of use

The following projects use swagger-routes-express as a starter template.

• My own api-server-boilerplate, and
• node-express-open-api-skeleton by Reuben Frimpong.

Note: If you have a template or example of use to add to this list please just raise a PR and I'll take a look.

Contributing

Please see the contributing notes.