Badly Formatted?

I will sometimes capture the JSON-based response body from another application to use as a fixture, but will end up with the standard one-liner file that is visually difficult to parse.

Surely Something Already Exists?

I looked around on the web and found a Python-based implementation, but it was padding with too many spaces and I had no insight into what it was actually doing. I spent a bit of time trying to see if I could make it conform to my needs, and shortly thereafter, decided to write it in Ruby.

Implementing A Custom Solution

The solution was quite simple once I knew how to pass in the current Vim file content (read: the buffer), how to access said content in Ruby, properly formatting it, and sending it back to Vim.

The basic Vim command I ended up with is

%!ruby -r json -e 'content =; object = JSON.parse(content); json = JSON.pretty_generate(object); puts json'

The Command Portion

%!ruby -r json -e
  1. % grabs the current file content / buffer
  2. !ruby calls Ruby
  3. -r json tells Ruby to require the json library
  4. -e tells Ruby to execute the code that follows

The Code Portion

# reads the content that Vim sent over
content =

# the content is still in JSON format, and it needs to be in object format
object = JSON.parse(content)

# the object then needs to be converted to "pretty" JSON
json = JSON.pretty_generate(object)

# outputting the "pretty" JSON sends it back to Vim
puts json

I actually ended up compressing the code to the following:

puts JSON.pretty_generate(JSON.parse(

In Action


Vim Commands

To make sure Vim always has this available, I bound it to a leader-based command in my .vimrc

nmap <leader>json :%!ruby -r json -e 'puts JSON.pretty_generate(JSON.parse('<CR>
vmap <leader>json :%!ruby -r json -e 'puts JSON.pretty_generate(JSON.parse('<CR>
imap <leader>json :%!ruby -r json -e 'puts JSON.pretty_generate(JSON.parse('<CR>

Now, with just a couple keystrokes, formatting JSON is as simple as I hoped it could be.