Add bootsnap to default Gemfile:

Bootsnap precomputes load path resolution and caches ruby ISeq
and YAML parsing/compilation, reducing application boot time by
approximately 50% on supported configurations.

Gemfile

@@ -54,6 +54,9 @@ gem "libxml-ruby", platforms: :ruby
 # Action View. For testing Erubis handler deprecation.
 gem "erubis", "~> 2.7.0", require: false
 
+# for railties app_generator_test
+gem "bootsnap", ">= 1.1.0", require: false
+
 # Active Job.
 group :job do
   gem "resque", require: false

Gemfile.lock

@@ -119,6 +119,8 @@ GEM
       childprocess
       faraday
       selenium-webdriver
+    bootsnap (1.1.0)
+      msgpack (~> 1.0)
     builder (3.2.3)
     bunny (2.6.2)
       amq-protocol (>= 2.0.1)
@@ -217,6 +219,7 @@ GEM
     mocha (0.14.0)
       metaclass (~> 0.0.1)
     mono_logger (1.1.0)
+    msgpack (1.1.0)
     multi_json (1.12.1)
     multipart-post (2.0.0)
     mustache (1.0.3)
@@ -384,6 +387,7 @@ DEPENDENCIES
   benchmark-ips
   blade
   blade-sauce_labs_plugin
+  bootsnap (>= 1.1.0)
   byebug
   capybara (~> 2.13)
   coffee-rails

railties/CHANGELOG.md

+*   Add `bootsnap` to default `Gemfile`.
+
+    *Burke Libbey*
+
 *   Properly expand shortcuts for environment's name running the `console`
     and `dbconsole` commands.
 

railties/lib/rails/generators/rails/app/templates/Gemfile

@@ -19,6 +19,9 @@ git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 # Use Capistrano for deployment
 # gem 'capistrano-rails', group: :development
 
+# Reduces boot times through caching; required in config/boot.rb
+gem 'bootsnap', '>= 1.1.0', require: false
+
 <%- if options.api? -%>
 # Use Rack CORS for handling Cross-Origin Resource Sharing (CORS), making cross-origin AJAX possible
 # gem 'rack-cors'

railties/lib/rails/generators/rails/app/templates/config/boot.rb

 ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../Gemfile', __dir__)
 
 require 'bundler/setup' # Set up gems listed in the Gemfile.
+require 'bootsnap/setup' # Speed up boot time by caching expensive operations.