ENVied

TL;DR ensure presence and type of your app's ENV-variables.

This gem will provide:

A fail-fast check for presence of ENV-variables
A fail-fast check whether the values can be coerced to the correct type
Access to typed ENV-variables (instead of just strings)

Quickstart

1) Configure

After successful installation, define some variables in Envfile:

# file: Envfile
variable :FORCE_SSL, :Boolean
variable :PORT, :Integer

2) Check for presence and coercibility

# file: some file that'll be run on initialization (e.g. `config/application.rb`)
ENVied.require

This will throw an error if:

not both ENV['FORCE_SSL'] and ENV['PORT'] are present.
the values can't be coerced to resp. Boolean and Integer.

3) Use coerced variables

Variables accessed via ENVied are of the correct type:

ENVied.PORT # => 3001
ENVied.FORCE_SSL # => false

Configuration

Types

The following types are supported:

:String (implied)
:Boolean (e.g. '0'/'1', 'f'/'t', 'false'/'true', 'off'/'on', 'no'/'yes' for resp. false and true)
:Integer
:Symbol
:Date (e.g. '2014-3-26')
:Time (e.g. '14:00')
:Hash (e.g. 'a=1&b=2' becomes {'a' => '1', 'b' => '2'})
:Array (e.g. 'tag1,tag2' becomes ['tag1', 'tag2'])

Groups

Groups give you more flexibility to define when variables are needed.
It's similar to groups in a Gemfile:

# file: Envfile
variable :FORCE_SSL, :Boolean

group :production do
  variable :NEW_RELIC_LICENSE_KEY
end

# For local development you would typically do:
ENVied.require(:default) #=> Only ENV['FORCE_SSL'] is required
# On the production server:
ENVied.require(:default, :production) #=> ...also ENV['NEW_RELIC_LICENSE_KEY'] is required

# BTW the following are equivalent:
ENVied.require
ENVied.require(:default)
ENVied.require('default')
ENVied.require(nil)

Defaults

In order to let other developers easily bootstrap the application, you can assign defaults to variables. Defaults can be a value or a Proc (see example below).

Note that 'easily bootstrap' is quite the opposite of 'fail-fast when not all ENV-variables are present'. Therefor you should explicitly state whén defaults are allowed:

# Envfile
enable_defaults! { ENV['RACK_ENV'] == 'development' }

variable :FORCE_SSL, :Boolean, default: false
variable :PORT, :Integer, default: proc {|envied| envied.FORCE_SSL ? 443 : 80 }

Please remember that ENVied only reads from ENV; it doesn't mutate ENV. Don't let setting a default for, say RAILS_ENV, give you the impression that ENV['RAILS_ENV'] is set.
As a rule of thumb you should only use defaults:

for local development
for ENV-variables that your application introduces (i.e. for ENV['STAFF_EMAILS'] not for ENV['REDIS_URL'])

A more extensive example

# Envfile
# We allow defaults for local development (and local tests), but want our CI
# to mimic our production as much as possible.
# New developers that don't have RACK_ENV set, will in this way not be presented with a huge
# list of missing variables, as defaults are still enabled.
not_production_nor_ci = ->{ !(ENV['RACK_ENV'] == 'production' || ENV['CI']) }
enable_defaults!(&not_production_nor_ci)

# Your code will likely not use ENVied.RACK_ENV (better use Rails.env),
# we want it to be present though; heck, we're using it in this file!
variable :RACK_ENV

variable :FORCE_SSL, :Boolean, default: false
variable :PORT, :Integer, default: 3000
# generate the default value using the value of PORT:
variable :PUBLIC_HOST_WITH_PORT, :String, default: proc {|envied| "localhost:#{envied.PORT}" }

group :production do
  variable :MAIL_PAAS_USERNAME
  variable :DATABASE_URL
end

group :ci do
  # ci-only stuff
end

group :not_ci do
  # CI needs no puma-threads, and sidekiq-stuff etc.
  # Define that here:
  variable :MIN_THREADS, :Integer, default: 1
  # more...
end

# Depending on our situation, we can now require the groups needed:
# At local machines:
ENVied.require(:default, :development, :not_ci) or
ENVied.require(:default, :test, :not_ci)

# At the server:
ENVied.require(:default, :production, :not_ci)

# At CI:
ENVied.require(:default, :test, :ci)

# All in one line:
ENVied.require(:default, ENV['RACK_ENV'], (ENV['CI'] ? :ci : :not_ci))

command-line interface

$ envied help
Commands:
  envied check           # Checks whether all ENV-variables are present and valid
  envied help [COMMAND]  # Describe available commands or one specific command
  envied init            # Generates a default Envfile in the current working directory

Installation

Add this line to your application's Gemfile:

gem 'envied'

...then bundle:

$ bundle

...and generate the Envfile:

$ bundle exec envied init

Testing

bundle install --binstubs

bin/rspec
# or
bin/rake

Developing

bin/pry --gem

Contributing

Fork it ( http://github.com/eval/envied/fork )
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Add some feature')
Push to the branch (git push origin my-new-feature)
Create new Pull Request