Unable to use http-proxy for all routes (/*) with @fastify/cors plugin

[kovalenp]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Fastify version

4.5.3

Plugin version

9.2.1

Node.js version

16.15.1

Operating system

macOS

Operating system version (i.e. 20.04, 11.3, 10)

13.4

Description

I need to allow CORS for my Fastify application. To achieve this I'm using @fastify/cors package with following settings:

    fastify.register(cors, {
      origin: '*',
      methods: ['GET', 'POST'],
      allowedHeaders: ['Content-Type', 'Authorization'],
      credentials: true,
    })

if I register the http-proxy route for something like this:

    .register(require('@fastify/http-proxy'), {
      upstream: 'https://some_url',
    })

I will get an error:

/node_modules/find-my-way/index.js:292
      throw new Error(`Method '${method}' already declared for route '${path}' with constraints '${JSON.stringify(constraints)}'`)
            ^
Error: Method 'OPTIONS' already declared for route '/*' with constraints '{}'
    at Router._on (/node_modules/find-my-way/index.js:292:13)
    at Router.on (/node_modules/find-my-way/index.js:136:10)
    at Object.addNewRoute (/node_modules/fastify/lib/route.js:262:16)
    at Object.route (/node_modules/fastify/lib/route.js:194:19)
    at Object._route [as route] (/node_modules/fastify/fastify.js:268:27)
    at fastifyHttpProxy (/node_modules/@fastify/http-proxy/index.js:291:11)
    at Plugin.exec (/node_modules/avvio/plugin.js:130:19)
    at Boot.loadPlugin (/node_modules/avvio/plugin.js:272:10)
    at processTicksAndRejections (node:internal/process/task_queues:83:21)

Probably because of this part of the lib:

  fastify.route({
    url: '/*',
    method: opts.httpMethods || httpMethods,
    preHandler,
    config: opts.config || {},
    constraints: opts.constraints || {},
    handler

Steps to Reproduce

Register fastify/cors with fastify/fastify-http-proxy for all routes

    fastify
    .register(cors, {
      origin: '*',
      methods: ['GET', 'POST'],
      allowedHeaders: ['Content-Type', 'Authorization'],
      credentials: true,
    })
    .register(require('@fastify/http-proxy'), {
      upstream: 'https://some_url',
    })

Expected Behavior

There is a way to enable cors on all routes for http-proxy plugin

PS:

I tried something like:

.register(require('@fastify/http-proxy'), {
      upstream: process.env.PUBLIC_API_URL,
      onResponse: (request: FastifyRequest, reply: FastifyReply) => {
        reply.header('Access-Control-Allow-Origin', '*')
        reply.header('Access-Control-Allow-Methods', '*')
        reply.header('Access-Control-Allow-Headers', '*')
      },
    })

but it didn't do the trick for me

[mcollina]

Thanks for reporting! Would you like to send a Pull Request to address this issue? Remember to add unit tests.

[amitkTechno]

hello @kovalenp
How did you resolve this issue? Thanks in advance.

[kovalenp]

@amitkTechno I didn't. You can remove /* route (if logic of your app allows to do so) and it will work, alternatively you could set the cors headers yourself

[psimk]

I managed to fix this by adding the prefix option:

await server.register(proxyPlugin, {
  prefix: "/api",
  upstream: "http://localhost:3002",
});

However, this does mean that now your clients will have to access the proxied server over the /api path.