any reason pop-to-buffer would be creating a new frame in my emacs?

and what would be the solution to stop it from doing that?

I don’t want new frames to be created, preferably just split windows

That doesn’t sound like default functionality. Are you using a pre-configured setup like Spacemacs or Prelude?

nope

Which Emacs distro and OS?

hrm

I’m using macOS Sierra

and emacs master 🙂

I thought Sierra was not released yet?

I don’t really know how to repro it, it really only happens in certain cases

yeah, it’s the public beta

Ah, OK.

specifically in haskell interactive mode

C-h f pop-to-buffer

If the window to show BUFFER is not on the selected
frame, raise that window's frame and give it input focus.

It sounds like the buffer is on a different frame to start with, and pop-to-buffer is just respecting that.

You would want to look at whatever is creating the buffer, probably.

actually the problem seems to be switch-to-buffer-other-window