Hapi: Cannot reply with stream in object mode

[hacdias]

What are you trying to achieve or the steps to reproduce?

I'm trying to use a stream as a reply.

const Transform = require('readable-stream').Transform

// ...

const output = new Transform({
  objectMode: true,
  transform (chunk, encoding, cb) {
    this.push(JSON.stringify(transformBandwidth(chunk)) + '\n')
    cb()
  }
})

res.pipe(output)
reply(output)
  .header('x-chunked-output', '1')

I tried removing the objectMode: true so I was changing it from a Stream in object mode to a regular Stream, but it didn't work and i received 'ERR_EMPTY_RESPONSE' instead.

What was the result you received?

Debug: internal, implementation, error
    Error: Cannot reply with stream in object mode
    at module.exports.internals.Response.internals.Response._streamify (D:\Code\ipfs\js-ipfs\node_modules\hapi\lib\response.js:580:30)
    at module.exports.internals.Response.internals.Response._marshal (D:\Code\ipfs\js-ipfs\node_modules\hapi\lib\response.js:558:21)
    at internals.state (D:\Code\ipfs\js-ipfs\node_modules\hapi\lib\transmit.js:80:18)
    at Items.parallel (D:\Code\ipfs\js-ipfs\node_modules\hapi\lib\transmit.js:459:20)
    at Object.exports.parallel (D:\Code\ipfs\js-ipfs\node_modules\items\lib\index.js:47:9)
    at Object.internals.state (D:\Code\ipfs\js-ipfs\node_modules\hapi\lib\transmit.js:452:11)
    at Object.internals.marshal (D:\Code\ipfs\js-ipfs\node_modules\hapi\lib\transmit.js:59:15)
    at Object.exports.send (D:\Code\ipfs\js-ipfs\node_modules\hapi\lib\transmit.js:30:15)
    at transmit (D:\Code\ipfs\js-ipfs\node_modules\hapi\lib\request.js:497:25)
    at Hoek.once (D:\Code\ipfs\js-ipfs\node_modules\hapi\lib\protect.js:50:16)

What did you expect?

The output on the browser.

Context

• node version: 9.2
• hapi version: 16.6.2
• os: Windows

[hacdias]

Apparently, wrapping it up with new Readable().wrap(output) makes it work. But why?

[hugomd]

@hacdias This is hacky, but you can pipe directly into the raw response object:

myStream.pipe(req.raw.response);

[hacdias]

Thanks for the tip @hugomd

[Marsup]

This should not be used like that, you're bypassing entirely hapi.

Your stream declares objectMode on both sides, it's normal that hapi rejects it. Use readableObjectMode and writableObjectMode.

[connor11528]

Not sure if it is related, but I am also getting this error when trying to return data from a route endpoint after reading a CSV file.

My endpoint is as follows:

server.route({
    method: 'POST',
    path: '/return_account_owner',
    config: {
        handler: (request, h) => {
            const { command, text, token } = request.payload;
            let accountOwner = null;
            let stream = fs.createReadStream('./accounts.csv');

            let csvStream = csv
                .parse()
                .on("data", function(data){
                    if(text == data[1]){
                        accountOwner = data[2];
                    }
                })
                .on("end", function(){
                     console.log(accountOwner);
                     return accountOwner;
                });

            return h.response(stream.pipe(csvStream))
                .type('text/event-stream')
                .header('Connection', 'keep-alive')
                .header('Cache-Control', 'no-cache');
        }
    }

Would it be best to use transforms and readable-stream like the OP for this scenario or is there another workaround for reading data from a stream and returning the result?

I am getting the same error Debug: internal, implementation, error Error: Cannot reply with stream in object mode. I'm using Hapi v17.3

[lock[bot]]

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