oak: Getting "The response is not writable." error

I had the same problem on routes that used a JWT auth middleware, my solution was to append await before my next() call, so instead of having:

if(token && csrfHeader) {
    if((await validateJwt(token, key)).isValid && validateCSRF(csrfCookie, csrfHeader)) {
       next()
    }

...

}

I changed it to:

if(token && csrfHeader) {
    if((await validateJwt(token, key)).isValid && validateCSRF(csrfCookie, csrfHeader)) {
       await next()
    }

...

}

It works fine, and no errors 😉

Apparently, for me the problem is that I didn’t return a Promise in the middleware, my code was something like this:

app.use((ctx, next) => {
  doSomething((result) => {
    ctx.response.body.result
    next()
  })
})

However, since I’m not return a promise, this line was immediately invoked even before doSomething finished, which will in turn turn the response unwritable.

So, by returning a promise as follows, I don’t face this problem anymore.

app.use((ctx, next) => {
  return new Promise(resolve => {
    doSomething((result) => {
      ctx.response.body.result
      resolve()
    })
  })
  .then(next)
})

Dear All,

I have the similar problem when using some middleware. The problem exist inside async await function, where if await is missed before next(). Please don’t forget to use await before next() or other method inside asycn function.

Regards

I also replaced next()

by await next()

–> this works fine in my case.

after this the controller content can be something like:

    getChatResponse: async ({ request, response }: { request: any; response: any }) => {
        const apiResult:any = await ResponseProvider.getResponse()
        response.body = apiResult
    }

it seems that the problem occurs because the function returns before the body is written, what I’m really confused by is that when using promises, oak awaits the promise and then disables writing but when using async/await, even though the function still returns a Promise<void>, it is not awaited

this error also occurs when I call: await Deno.readFile …

I have create a repo with a small example of where I have been hitting this issue.

https://github.com/LukeShay/oak-response-not-writable

@kitsonk I think it might be worthwhile to re-evaluate #156, considering that most of the users that face this error is due to human error rather than library bug, which can be avoided with the stricter middleware types.

Same error here.

When I try to fetch asynchronously some data from my DB with mongo@v0.7.0, I get The response is not writable error.

.post('/uploadFile/:projectId', upload('uploads'), async(context: any)=>{
  // Do stuff
  const project: Project | undefined = await projects.findOne({
    _id: { "$oid": context.params.projectId}
  })
  // Do stuff
  context.response.body = 'Any response'
})

If I remove this DB request, everything works fine, but this await seems to cause the problem. Could be upload middleware doing somthing here?

BTW, I found a way to make it work, moving this request to a middleware and passing the information I need through the context.

const checkProject = async(context: any, next: any) => {
  const project = await projects.findOne({_id: { $oid: context.params.projectId}})
  if(project){
    context.project = project
    await next()
  }
}

 // ...
router
  .post('/uploadFile/:projectId', checkProject, upload('uploads'), async(context: any)=>{
  // Do stuff
  const project: Project | undefined = context.project
  // Do stuff
  context.response.body = 'Any response'
}))

}