Help with asyncproc simultaneous stdout & stderr?

[akavel]

Hi, I'm trying to write an app that could start a subprocess, and react to its stdout or stderr, depending on what shows up. I was given some initial advice on Nim forum, and I tried to build something based on it, but I think I must be doing something wrong, as I'm not getting results I was expecting :( I have files like below:

q_async.nim

import asynctools/[asyncproc, asyncpipe]
import asyncfutures
import asyncdispatch

var p = startProcess("q_outerr", options = {})
var pout = p.outputHandle
var perr = p.errorHandle

proc next() {.async.} =
  var bufo = newString(1)
  var fo = pout.readInto(bufo[0].addr, bufo.len)
  var bufe = newString(1)
  var fe = perr.readInto(bufe[0].addr, bufe.len)
  var fx = p.waitForExit()
  while true:
    await fe or fo or fx
    if fo.finished:
      if fo.read > 0:
        echo "O ", fo.read(), " ", bufo.substr(0, fo.read()-1)
      fo = pout.readInto(bufo[0].addr, bufo.len)
    if fe.finished:
      if fe.read > 0:
        echo "E ", fe.read(), " ", bufe.substr(0, fe.read()-1)
      fe = perr.readInto(bufe[0].addr, bufe.len)
    if fx.finished:
      echo "X ", fx.read()
      return
    if fo.finished and fe.finished and fo.read==0 and fe.read==0:
      return

waitFor next()

q_outerr.nim

import os

stderr.writeLine "some stderr"
stderr.writeLine "some stderr2"
stdout.writeLine "some stdout2"
stderr.writeLine "some stderr3"
stderr.writeLine "some stderr4"

Results

Now, when I compile both, and run q_async.exe (on Windows), I'm getting output like below:

C:\prog\mana>q_async
O 1 s
E 1 s
O 1 o
X 0

If I remove fx from q_async, it's just hanging at some point, still not printing all output from q_outerr.

Do you have any idea what I might be doing wrong, and how I could make this work correctly, to display all stdout & stderr from q_outerr.nim?

[akavel]

Hmmmm; not sure but I might have fixed this by using waitFor instead of await, and making proc next non-async. Is that what I should be doing?