ConfigSL

ConfigSL is a simple Domain-Specific Language (DSL) module for configuration. It is designed to provide a declarative way to define configuration, with as few dependencies and additional cruft as possible. It is both modular and extensible, so you can use as little or as much as you need.

Installation

Add this line to your application's Gemfile:

gem 'configsl'

And then execute:

bundle install

Or install it yourself as:

gem install configsl

Usage

You can start defining your configurations using two methods:

1. Extend the included ConfigSL::Config base class
2. Include the ConfigSL modules you want to use in you class

Using the included base class

The ConfigSL::Config base class includes common functionality for working with configurations. Currently, the class provides the following features:

• DSL: The primary DSL for defining configuration options
• Format: A simple way to enforce option value formatting
• FromEnvironment: Load configuration from environment variables
• FromFile: Load configuration from a file
• Validation: Built-in validation for configuration options

require 'configsl'

class AppConfig < ConfigSL::Config
    register_file_format :json
    register_file_format :yaml

    option :name, type: String, default: 'My App'
    option :environment, type: Symbol, enum: %i[dev test prod], default: :dev,
                         env_variable: 'RACK_ENV'
    option :database, type: DatabaseConfig, required: true
end

Including modules

If you'd like to pick and choose the features you want to use, you can include modules individually. Most modules can be included in any order, but the DSL module must be included before any others.

Additionally, you will need to implement initialize -- or some other method -- that sets the configuration values by calling set_value for each option.

require 'configsl'

class ApplicationConfig
    include ConfigSL::DSL
    include ConfigSL::Format
    include ConfigSL::FromEnvironment

    option :name, type: String, default: 'My App'
    option :environment, type: Symbol, env_variable: 'RACK_ENV'
    option :database, type: DatabaseConfig

    def initialize(params = {})
      params.each do |name, value|
        set_value(name, value)
      end
    end
end

A note about inheritance

When working with multiple configuration classes, you'll likely want to use a base class. This could be the ConfigSL::Config class, or a custom class that includes the modules you need.

While the modules you include are inherited by subclasses, any options you define via DSL are not. This is because these values are stored using class instance variables. As a result, if you have options that are shared between classes, they will need to be implemented in both.

It's important to note that this is not limited to your defined configuration options, but also methods such as register_file_format and config_file_path.