Working with REPLs in VIM

Published: April 24, 2020

Working with Postgres and R recently, I had found some solution for getting my stuff from my VIM to their respective REPLs. That’s how I came up with this solution.

I’m a minimalist, and I like command lines. So the idea of having to use an IDE gives me nightmares.

Recently I’ve been playing a lot with Postgres. Of course, I exclusively used the psql interactive terminal. It uses Readline, so it feels like any REPL does. It has a few nice key-bindings, but I always end up feeling impaired and craving my familiar VIM environment¹.

Now being a minimalist, I don’t like installing a plugin for every REPL I use. So I thought about what alternatives there were. What if you were to integrate your REPL into VIM somehow?

Theoretically, I could simply create a key-binding that sends yanked lines to a command-line. That could look like this "psql -h ... -c " . getreg(0). However, this is pretty clumsy. You lose all the nice parts of the interactive shell, and you always have your command output move your file out of the screen. So you can’t look at both your query while checking the result.

After searching around for a bit, I found :ter in the VIM 8.1 release notes. :ter was exactly what I wanted. With :ter psql -h ... you open up a window with the Postgres terminal in it. So you can either go around copy pasting your command-lines, or you can simply write a command for it.

Here’s the minimal version I’ve been using for the past few weeks:

nmap <silent> <leader>s :set opfunc=ExecuteAsCommand<CR>g@

let s:term_buffer = ''
function ExecuteAsCommand(type, ...)
  silent exe "normal '[\"cy']"
  echo s:term_buffer

  " clear the screen (and quit less if its open)
  call term_sendkeys(s:term_buffer, "q")
  call term_sendkeys(s:term_buffer, "\<C-c>")
  call term_sendkeys(s:term_buffer, "\<C-l>")

  call term_sendkeys(s:term_buffer, getreg('c'))
endfunction

command! -nargs=1 Run call RunTerminalCommand(<f-args>)<CR>
function RunTerminalCommand(command)
  execute 'ter ' . a:command
  let s:term_buffer = a:command
endfunction

After having loaded this, :Run psql -h ... opens up a terminal window with psql. And now entering <leader>s{motion}² sends the text you moved over to your terminal.

This little snipped is my favourite thing I’ve discovered in VIM in quite while. It’s now a central part of my number-crunching workflow. I’m going to write a post about that soon as well.

In psql \e scratched the VIM itch somewhat. You can edit your last command in your $EDITOR. ↩︎
The snippet above only works for whole lines selected with a motion. I try to use visual-mode as little as possible. If you’d like to add support for visual mode, that’s easy to do. Have a look at :help :map-operator. ↩︎