pry zle

Fo' shizzle, ma' pryzzle.

Pry's default terminal interaction is via Readline. As we start to want more functionality, this is going to prove an obstacle.

Readline

Readline has never been that great:

• Look at the vicious hack used to add a binding into it. I don't see the API to simply bind a key. For example, Readline.vi_editing_mode is just C calls.
• Writing actual extensions is harder. I don't know how we could define a custom function that libreadline could call. To get a custom function when inside bash, you do like: bind -x * '"\ep":"foo"' and then the function has read/write vars $READLINE_LINE and $READLINE_POS, but that's about it. Contrast that with the expressiveness zle funcs.
• It doesn't do multiline stuff. Compare the Bash handling of a multi-line command input + recall versus the Zsh equivalent. Zsh keeps it splayed out on several lines, but Bash canonicalizes it as a one-liner. Our Pry experience is even worse on this one, as it chops multiline input up into individual history entries, so recalling basically requires edit (and then you've lost REPL powers).
• It has no "Menu" output like zle -M. To see the widget I'm talking about in action in zsh, tabcomplete something. It will show a temporary menu hanging below the prompt, which goes away any time you tabcomplete something else or when you hit Enter.
• Bad OS X support by default (e.g. the libedit backend doesn't support emacs + vi modes)
• Requires libreadline-dev to be present when Ruby is built.

Coolline

Coolline is interesting, but very incomplete.

• No easily-made "Sub-modes". E.g. if you wanted to do vi's daw it would require making d swap in a different :handlers value.
• No undo.
• No repeat.
• No registers (~copy & paste)
• Hard-codes terminal sequences (e.g., no $TERM handling; no support for degraded functionality)
• Also does no multiline editing.
• Also has nothing like zle -M

We could get to the point where we have all of these things, and it'd be nice because it would all be in-house and malleable, but it's so much work.

I really think the solution is:

The Zsh Line Editor

The software is the best command-line interaction I've dealt with.

I think using it would be smoothest if we had a 2nd I/O channel for Pry, so that the normal $stdout would work, but that we could also query it for completion, show-doc output, show-source, etc.

Another option entirely:

LeoNerd's stuff

Several of his projects are relevant.

• libtermkey - Keyboard input
• libtickit - UI (input via libtermkey)
• …several others.

The advantage here is that he's committed and very knowledgeable about terminals.