Setting request header or prefer c.get()?

[exoup]

Howdy!

I'm writing a middleware to pass some necessary information in requests that my application receives.

Is there a known method to set a custom request header for a HonoRequest or is it preferred not to modify the request header and instead just pass required data via the Context getter and setter?

Can I modify c.req.raw.header somehow?

[6km]

Hi @exoup

It's possible to pass data using the following techniques (not just these)

Setting a custom request header

It can be done using the c.req.raw.headers.set() method but it should be before calling next().

Please notice that when you set a request header from the server side, it will not be passed to the client side. This technique is only used to pass data to the route handler.

app.use(async (c, next) => {
  c.req.raw.headers.set('x-username', '6km')
  await next()
})

app.get('/', (c) => {
  const passedData = c.req.header('x-username')
  // ...
})

---

Setting a custom response header

This technique is used to pass data to the server through response headers.

To set a response header, it's simple, just use c.header(name, value).

app.use(async (c, next) => {
  await next()
  c.header('x-username', '6km')
})

---

Passing data through Context

Set the value specified by the key with set and use it later with get.
This can be used to pass methods and additional data.

type Variables = {
  username: string
}

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

app.use(async (c, next) => {
  c.set('username', '6km')
  await next()
})

app.get('/', (c) => {
  const passedData  = c.get('username')
  // ...
})

[exoup]

@6km Appreciate the thorough response.

I was initially using c.req.raw.headers.set() to set my headers but kept running into a TypeError: Headers are immutable error.

Despite not using upgradeWebSocket anywhere, I suspect I'm running into this issue #2535.
I'll just stick with the Context object.

Thanks!

[6km]

You're welcome! By the way, which version of Hono are you using? Try the latest one.

[exoup]

You're welcome! By the way, which version of Hono are you using? Try the latest one.

I was using 4.3.11 but the issue also exists in 4.4.0, but it's all right.

[6km]

I was using 4.3.11 but the issue also exists in 4.4.0, but it's all right.

Oh, I hope it gets fixed asap!

[yusukebe]

Hi. Regardless of whether you are using upgradeWebSocket or not, c.req.raw.header - a Headers object can be immutable. So, please use c.header()!