Automatic object stream piping

[mcollina]

Currently, we cannot pass a standard objectMode stream inside a channel with automated piping: we need to create a new channel and pipe.

Is it sound to use that pattern? Plus, solving this issue might be more tricky, because Transform stream are not supported by the automated piping natively, you will need to flag them with something like jschanReadable or jschanWritable.

Any opinions on this?

[davidmarkclements]

Hey @mcollina can you elaborate with some (pseudo) code?

[mcollina]

So you might want to use a https://www.npmjs.org/package/from2 fro generating some events to pop to a client.

Right now you have to do:

session.on('channel', function(chan) {
  chan.on('data', function(msg) {
    var chan = chan.WriteChannel()
    from2(...).pipe(chan)
    msg.returnChannel.end({
      more: chan,
      error: false
    })
  })
})

Using graft syntax:

through.obj(function(msg, enc, done) {
    var chan = msg._channel.WriteChannel()
    from2(...).pipe(chan)
    msg.returnChannel.end({
      more: chan,
      error: false
    })
})

However, with this you might want to use:

through.obj(function(msg, enc, done) {
    msg.returnChannel.end({
      more: from2(...),
      error: false
    })
})

and it gets automatically piped.

This would also greatly help seneca integration, as at that point it could just forget about channels.

The only point will be Transform streams, which must get an isReadChannel or isWriteChannel property hooked up.

[davidmarkclements]

could we abstract the pain by doing the channel switching under the hood in response to a pipe event?

[AdrianRossouw]

deja vu? #22

[mcollina]

@AdrianRossouw this is the missing bit for #22. However it requires some changes to msgpack5.

@davidmarkclements for sure! This requires some changes to msgpack5, if you want to help we can discuss the details there.