WebsocketHandler Request generics don't work the same as http Handlers

🐛 Bug Report

In a TypeScript project, I am using the new 3.0.0 WebsocketHandler interface that provides FastifyRequest. I want to declare the request Header type so I can access them without casting or using //@ts-ignore as I do with HTTP request handlers.

Here is an example

  server.get("/ws",  {
      websocket: true,
      schema: {
        headers: TenantHeaderSchema
      }
    },
    // compiler error, see below
    createWSHandler())

...

function createWSHandler() {
  return (conn:     SocketStream,
          request:  FastifyRequest<{Headers: TenantHTTPHeader}>) => {
    const {tenant} = request.headers
...

Here is the compiler error:

 Overload 1 of 4, '(path: string, opts: RouteShorthandOptions<Server, IncomingMessage, ServerResponse, RequestGenericInterface, unknown> & { ...; }, handler?: WebsocketHandler | undefined): FastifyInstance<...>', gave the following error.
    Argument of type '(conn: SocketStream, request: FastifyRequest<{    Headers: TenantHTTPHeader;}>) => void' is not assignable to parameter of type 'WebsocketHandler'.
      Types of parameters 'request' and 'request' are incompatible.
        Type 'FastifyRequest<RouteGenericInterface, Server, IncomingMessage>' is not assignable to type 'FastifyRequest<{ Headers: TenantHTTPHeader; }, Server, IncomingMessage>'.
          Type 'RouteGenericInterface' is not assignable to type '{ Headers: TenantHTTPHeader; }'.
            Types of property 'Headers' are incompatible.
              Type 'unknown' is not assignable to type 'TenantHTTPHeader'.

Expected behavior

I expect the FastifyRequest declaration to accept Headers declarations as they do in other get() handlers. An example that works with the same schema and types is below:

  server.get("/data", {
      schema: {
        headers: TenantHeaderSchema
      }
    },
    createGetDataHandler())

...

function createGetDataHandler() {
  return async (request:  FastifyRequest<{Headers: TenantHTTPHeader}>,
                reply:    FastifyReply) => {
    const {tenant} = request.headers

Your Environment

• node version: 12.20.0
• fastify version: >=3.11.0
• fastify-websocket version: 3.0.0
• os: Mac

[mattbishop]

This issue has been fixed by https://github.com/fastify/fastify-websocket/pull/112

Thanks!

[Ethan-Arrowood]

Could you merge over the RouteOptions type instead?