Per-route context Variables with upgradeWebSocket

[moroshko]

What is the feature you are proposing?

Currently, context variables can be defined in normal (non-WebSocket) routes like this:

type ContextVariables = {
  foo: number;
}

const app = new Hono<{ Variables: ContextVariables }>();

app.get('/', (c) => {
  const foo = c.var.foo; // number
  ...
})

But, when using upgradeWebSocket from hono/bun, the types don't work:

import { createBunWebSocket } from 'hono/bun'
import type { ServerWebSocket } from 'bun'

const { upgradeWebSocket, websocket } = createBunWebSocket<ServerWebSocket>()

type ContextVariables = {
  foo: number;
}

const app = new Hono<{ Variables: ContextVariables }>()

app.get(
  '/ws',
  upgradeWebSocket((c) => {
    const foo = c.var.foo; // any
    ...
  })
)

Globally extending ContextVariableMap is problematic when the app has multiple routes where every route has its own context fields:

declare module 'hono' {
  interface ContextVariableMap {
    foo: number;
  }
}

It would be nice to have the ability to specify context variables per WebSocket route, e.g.:

app.get(
  '/ws1',
  upgradeWebSocket<{ Variables: { foo: number, bar: boolean } }>((c) => {
    const foo = c.var.foo; // number
    const bar = c.var.bar; // boolean
    ...
  })
)


app.get(
  '/ws2',
  upgradeWebSocket<{ Variables: { foo: string } }>((c) => {
    const foo = c.var.foo; // string
    const bar = c.var.bar; // Property 'bar' does not exist...
    ...
  })
)

[yusukebe]

Thanks!

This is related to #3202