Stream first, write later

main.lua

@@ -206,8 +206,22 @@ shell_router.execute_request = function (sock, msg)
    end
    if func then
       pok = true
-      -- TODO: for lua outputs to be streamed from the executing command (for example a long for-loop), redefine 'print' to stream-out pyout messages
+
+      local _print = print
+      local buf = ''
+      print = function(text)
+        buf = buf..text
+        iopub_router.stream(iopub, msg, 'stdout', text)
+      end
+
       ok,err = xpcall(func, traceback)
+
+      local m = util.msg('clear_output', msg)
+      m.content = {wait=true, display=true}
+      util.ipyEncodeAndSend(iopub, m)
+
+      print = _print
+      print(buf)
    else
       ok = false;
       err = perr;