Question regarding creating transport pipeline

[rluvaton]

In the docs the following code example is shown for Creating a transport pipeline

import build from 'pino-abstract-transport'
import { pipeline, Transform } from 'stream'
export default async function (options) {
  return build(function (source) {
    const myTransportStream = new Transform({
      // Make sure autoDestroy is set,
      // this is needed in Node v12 or when using the
      // readable-stream module.
      autoDestroy: true,

      objectMode: true,
      transform (chunk, enc, cb) {

        // modifies the payload somehow
        chunk.service = 'pino'

        // stringify the payload again
        this.push(`${JSON.stringify(chunk)}\n`)
        cb()
      }
    })
    pipeline(source, myTransportStream, () => {})
    return myTransportStream
  }, {
    // This is needed to be able to pipeline transports.
    enablePipelining: true
  })
}

1. Why objectMode: true and not writableObjectMode: true? as we read object from source but we write string
2. Why need to call pipeline if the worker-pipeline.js already does that:
   

   pino/lib/worker-pipeline.js

   Lines 28 to 35 in 1aacfd2

   	pipeline(stream, ...streams, function (err) {
   	if (err && err.code !== 'ERR_STREAM_PREMATURE_CLOSE') {
   	ee.emit('error', err)
   	return
   	}
   	ee.emit('closed')
   	})

[mcollina]

Why objectMode: true and not writableObjectMode: true? as we read object from source but we write string

backward compatibility and good habits. Those did not exist some time ago.

Why need to call pipeline if the worker-pipeline.js already does that:

because A Duplex is created: https://github.com/pinojs/pino-abstract-transport/blob/b6d7973a80b115b9bad3098efb669279ff9667c9/index.js#L70

[rluvaton]

Thanks!