Why does IHaskell output stdout/stderr as display_data instead of stream?

[thomasjm]

Apologies if this has already been answered, but I couldn't find it.

When you run a simple print like putStrLn "hi", IHaskell outputs it as a Jupyter display_data output like the following:

    {
     "output_type": "display_data",
     "metadata": {},
     "data": {
      "text/plain": [
       "\"hi\""
      ]
     }
    }

Most Jupyter kernels would output this using the stream type. For example, if I run print("hi") in the Python kernel, I get:

    {
     "output_type": "stream",
     "name": "stdout",
     "text": [
      "hi\n"
     ]
    }

It doesn't cause any major problems, but it does render slightly differently in the notebook and can cause confusion for other tools that try to deal with output from Jupyter notebooks (such as papermill).

Is there a reason it works this way? Would you accept a PR to change it? Thanks in advance for any clarification.

[vaibhavsagar]

I'm not aware of any reason we use display_data instead of stream here, but I worry this might be a bigger change than it appears to be at first. I'd welcome a PR.