Spring Documentation

Spring automatically detects environment changes. If you run a command with a different environment (e.g., using RAILS_ENV), Spring will boot that specific environment.

For rake tasks, they run in the development environment by default, but you can change this using the RAILS_ENV environment variable.

Spring is a Rails application preloader that keeps your application running in the background to speed up development tasks like running tests, rake tasks, or migrations.

To set it up:

1. Add spring to your Gemfile in the :development group.
2. Run bundle install.
3. 'Springify' your bin/ directory by running bundle exec spring binstub --all. This generates a bin/spring executable and modifies existing executables to hook into Spring.

Note: Using gem "spring", git: "..." is not supported.

gem "spring", group: :development

$ bundle install
$ bundle exec spring binstub --all

Spring should not be installed in production environments. To ensure it is excluded during deployment, configure Bundler to skip the development and test groups before running bundle install on your production machine.

$ bundle config set without 'development test'
$ bundle install

To completely remove Spring from your Rails application:

1. 'Unspring' your bin/ executables using bin/spring binstub --remove --all.
2. Remove the spring gem from your Gemfile.

You can use Spring without checking it into your source repository by installing it as a system gem and prefixing your commands with spring instead of using binstubs.

Note: Using Spring binstubs without adding Spring to the Gemfile is not supported.

If you are working on a project with a non-standard setup (such as a Rails engine), you must manually specify the application root in a config/spring.rb file relative to the engine's root directory.

Spring.application_root = './test/dummy'

Spring relies on Rails' application reloading mechanism. To ensure it works correctly, you must ensure config.enable_reloading is set to true in your environment configurations (e.g., config/environments/test.rb).

For Rails versions before 7.1: You must set cache_classes to false instead.

To disable the "Running via Spring preloader" message, you can either:

1. Set Spring.quiet = true in ~/.spring.rb or config/spring.rb.
2. Set the SPRING_QUIET environment variable before executing Spring commands.

Spring loads configuration from two main files:

1. ~/.spring.rb: Loaded before Bundler. Use this to require spring-commands-* gems that you want available in all projects without adding them to every project's Gemfile.
2. config/spring.rb: Loaded after Bundler. Use this for project-specific settings.

Additionally, config/spring_client.rb is loaded before Bundler and before a server process starts; it can be used to add new top-level commands.

If you need to see detailed information about Spring's activity, run the server explicitly in a separate terminal. Logging output will be printed to stdout, or you can redirect it to a file using the SPRING_LOG environment variable.

$ spring server

To run code after Spring has forked the process but before the actual command is executed (e.g., for connecting to external services, performing cleanup, or setting up dynamic configuration), use the Spring.after_fork callback. You can register multiple callbacks by calling the method multiple times.

Spring.after_fork do
  # run arbitrary code
end