envp

Envp

A Ruby gem for working with environment variables much like OptionParser does with command-line arguments.

Installation

Install the gem and add to the application's Gemfile by executing:

$ bundle add envp

If bundler is not being used to manage dependencies, install the gem by executing:

$ gem install envp

Usage

Envp allows you to write expectations for environment variables for your program.

Simple example

Define a program in a new file app.rb:

reqiure 'envp'

pp Envp.parse do |e|
  e.required("FOO")
end

Run the program without any special environment variables:

$ ruby app.rb
app.rb:47:in `handle_errors': FOO: missing required value (Envp::Failure)
  from app.rb:26:in `parse'
  from -e:1:in `<main>'

Rather then let the program continue with missing required values, an exception is raised immediately.

Run the program with the required environment variables:

$ FOO=bar ruby app.rb
{"FOO"=>"bar"}

The specified environment variables are parsed into a Ruby hash for use in your program.

Coercions

Environment variables can be coerced from string values into richer types. For example, to parse a value into an integer:

reqiure 'envp'

pp Envp.parse do |e|
  e.required("FOO", Integer)
end

Will result in:

$ FOO=123 ruby app.rb
{"FOO"=>123}

Along with various predefined coercions, you can define your own coercions:

reqiure 'envp'

pp Envp.parse do |e|
  e.accept(User) do |id|
    User.find(id)
  end
  e.required("USER_ID", User)
end

Full example

The following example demonstrates all features:

Envp.parse(constants: true, symbolize: true, normalize: true) do |e|
  e.accept(User) do |id|
    User.find(id)
  end
  e.required("USER_ID", User)
  e.required("API_KEY", allow_blank: false) do |value|
    DEFAULT_LOGGER.debug("using API_KEY #{value}")
  end
  e.optional("DEBUG", :bool, default: false)
end
# => {:user_id=>#<User...>, :api_key=>"abc123", :debug=>false}
Envp::DEBUG # => false
Envp::API_KEY # => "abc123"

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/avdgaag/envp. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the Envp project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.