Fastify 3.10 breaks prefixed plugins

[Skn0tt]

🐛 Bug Report

Fastify 3.10, together with the use of prefixes, breaks fastify-websocket.

fastify.register(
  (fastify, opts, done) => {
    fastify.get("/", { websocket: true }, (connection, req) => {
      connection.socket.send("This works");
    });

    done();
  },
  { prefix: "/activity" }
);

To Reproduce

• Clone https://github.com/Skn0tt/fastify-websocket-3.10-repro
• Run index.js
• Connect to ws://localhost:3000/activity

Your Environment

• node version: 15.3
• fastify version: >=3.10
• os: Mac

Some ideas as to what may be causing this

Prior to 3.10, this line was called twice per route:

fastify-websocket/index.js

Line 36 in 99c94a0

fastify.addHook('onRoute', routeOptions => {

That's why this lines makes sure to ignore one of them:

fastify-websocket/index.js

Line 42 in 99c94a0

if (routeOptions.path === routeOptions.prefix) {

Now with 3.10, the onRoute is called only once, and all of the routes are effectively ignored.

originally encountered in quirrel-dev/quirrel#49

[mcollina]

I agree with your analysis! Would you like to send a PR to fix this module?

[mcollina]

Please check out #98, it should fix the problem.