24 Nov 2021

Awesome Bundler Feature: Inline Gemfiles

Ruby’s Bundler introduced a feature that I’m loving for prototypes and quick scripting

Inline Gemfiles

Introduced in v1.10, these avoid needing a separate declaration of a Gemfile and you write it directly into the script you’re creating.

It fixes the following ergonomic issues:

  • Writing a separate Gemfile when your program is a single Ruby script is overkill
  • Packaging your Gemfile to accompany aforementioned script is a hassle
  • For single file scripts you can now rely on Gems!

How To Use It

require 'bundler/inline'

# Declare Gemfile in ruby script
gemfile do
  source 'https://rubygems.org'
  gem 'mongo'
  gem 'pry'

client = Mongo::Client.new(ENV.fetch('MONGO_URL'))


I’m not writing much Ruby these days because I work leading engineers, but when I hack on things in my spare time I’m prototyping and want to iterate on an idea before converting it to Golang. I did this recently when iterating on how to speed up controlled MongoDB failovers and when spiking out a terraform-like system for MongoDB configuration management.

Bundler-inline is great for these situations because they’re a single Ruby script but require installing Gems :).