Hono•4d ago

Type safety in middleware?

Hi, it's there a way to get the types right here?

import { Hono } from "hono"
import { hc } from "hono/client"

export const honoApp = new Hono()
  .use(async (c, next) => {
    await next()
    if (Math.random() > 0.5) {
      return c.json({ authenticated: false }, 401)
    }
  })
  .get("/", (c) => {
    if (Math.random() > 0.5) {
      return c.json({ message: "ok" }, 200)
    }
    return c.json({ error: "internal error" }, 500)
  })

// eslint-disable-next-line @typescript-eslint/no-unused-vars
const _honoClient = hc<typeof honoApp>("/")
type HonoClient = typeof _honoClient

const createHonoClient = (...args: Parameters<typeof hc>): HonoClient => hc<typeof honoApp>(...args)

export const honoClient = createHonoClient("/")
honoClient.index.$get().then(async (res) => {
  const data = await res.json()
  console.log(data)
})

import { Hono } from "hono"
import { hc } from "hono/client"

export const honoApp = new Hono()
  .use(async (c, next) => {
    await next()
    if (Math.random() > 0.5) {
      return c.json({ authenticated: false }, 401)
    }
  })
  .get("/", (c) => {
    if (Math.random() > 0.5) {
      return c.json({ message: "ok" }, 200)
    }
    return c.json({ error: "internal error" }, 500)
  })

// eslint-disable-next-line @typescript-eslint/no-unused-vars
const _honoClient = hc<typeof honoApp>("/")
type HonoClient = typeof _honoClient

const createHonoClient = (...args: Parameters<typeof hc>): HonoClient => hc<typeof honoApp>(...args)

export const honoClient = createHonoClient("/")
honoClient.index.$get().then(async (res) => {
  const data = await res.json()
  console.log(data)
})

I expected data to be

const data: {
    message: string;
} | {
    error: string;
} | {
    authenticated: boolean;
}

const data: {
    message: string;
} | {
    error: string;
} | {
    authenticated: boolean;
}

But actually it is

const data: {
    message: string;
} | {
    error: string;
}

const data: {
    message: string;
} | {
    error: string;
}

6 Replies

ambergristle•4d ago

https://hono.dev/docs/guides/rpc#status-code you can narrow the type client side using response.ok or response.status for just the types, you can use hono's InferResponseType utility type, which accepts an optional status code param that narrows the returned union

Gary, el Pingüino ArtefactoOP•4d ago

you can't narrow a type that isn't present...

Gary, el Pingüino ArtefactoOP•4d ago

found this https://github.com/honojs/hono/issues/3746

GitHub

MiddlewareHandler response type inference · Issue #3746 · honojs/ho...

What is the feature you are proposing? When we use middleware, it can return a Response object or a Typed Response, for example, @hono/validator returns a MiddlewareHandler that can return a respon...

ambergristle•4d ago

ah yeah, my bad. definitely didn't read your snippets closely enough i remember seeing the response type from the middleware in the json and thinking "huh, ig that works after all"

Gary, el Pingüino ArtefactoOP•4d ago

it's okay, I think it is a well known issue so I have to find another way thanks for the help 😄

ambergristle•4d ago

yeah, i was just chatting w someone else who had the same issue np!

Gaming

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Type safety in middleware?

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