svoid vmBus_snoopToPrint(IPred<S> shouldPrintMsg) {
  assertNotNull(shouldPrintMsg);
  
  vmBus_snoopToPrint((msg, arg) -> shouldPrintMsg.get(msg));
}

svoid vmBus_snoopToPrint(IF2<S, O, Bool> shouldPrintMsgWithArgs) {
  assertNotNull(shouldPrintMsgWithArgs);
  
  ownResource(vmBus_onAnyMessage(voidfunc(S msg, O _arg) pcall {
    O arg = _arg;
    if (!shouldPrintMsgWithArgs.get(msg, arg)) ret;
    if (arg instanceof O[]) arg = joinWithComma(allToString((O[]) arg));
    S s = msg + (arg == null ? "" : " | " + arg);
    print(localTimeWithSeconds() + " " + shorten(s, 200));
  }));
}

Began life as a copy of #1019633