Accessing Parent Params in Nested .route() Handlers

[kevinsimper]

Hi Hono community,

When using nested routes via .route(), handlers in the child route don't seem to have direct access to parameters defined in the parent route.

Example:

import { Hono } from 'hono'

const app = new Hono()
const postApp = new Hono()
const commentsApp = new Hono()

// Desired structure: GET /posts/123/comments
// But 'postId' isn't available in commentsApp handlers

commentsApp.get('/', (c) => {
  const postId = c.req.param('postId') // This is type error
  return c.text(`Comments for Post ${postId ?? 'ID NOT FOUND'}`)
})

postApp.route('/:postId/comments', commentsApp)
postApp.get('/:postId', ...)


// Define :postId here
app.route('/posts', postApp)

export default app

Because postId isn't available in commentsApp, a common workaround is to restructure the routes like this:

// Workaround Structure
const commentsAppWorkaround = new Hono()

commentsAppWorkaround.get('/:postId', (c) => {
  const postId = c.req.param('postId') // Now this works
  return c.text(`Comments for Post ${postId}`)
})

// Define :postId *after* /comments
app.route('/posts/comments/', commentsAppWorkaround)

Question:

Is this restructuring (e.g., /posts/comments/:postId instead of /posts/:postId/comments) the idiomatic way in Hono to handle nested resources needing parent IDs when using separate Hono instances with .route()? Or is there a better pattern to access parent parameters directly within the nested route handlers?

Thanks!

[BB-FilZembowicz]

This would be nice if it were somehow built in

My workaround is just to stick the :postId in the context

In the post logic:

.use("/comments/*", async(c, next) {
  c.set('postId', postId);
  await next();
}

Then in the nested routes you can do

const postId = c.get('postId')

This won't be typed by default, but if you define the Variables option of the Hono generic type it can be set correctly

const api = new Hono<{ Variables: { postId: string }>().get(....).post(...)