Default to Rails.env for env, don't double-write constants if avoidable

README.md

@@ -5,7 +5,17 @@ If your app relies on lots of environment secrets, onboarding's tough. New team
 You can use `Nvar` in Ruby apps, with out-of-the-box support provided for Rails.
 ## Installation
 
-Add the gem to your Gemfile and install it with `bundle add nvar`. If you're not on Rails, you'll need to make sure that `Nvar` is required with `require 'nvar'`, and then manually call `Nvar::EnvironmentVariable.load_all` as early as is appropriate.
+Add the gem to your Gemfile and install it with `bundle add nvar`. If you're not on Rails, you'll need to make sure that `Nvar` is required with `require 'nvar'`, and then manually call `Nvar.load_all` as early as is appropriate.
+
+It's recommended to do this by adding the following to `config/application.rb`:
+
+```rb
+require "dotenv/load" # if using in tandem with dotenv
+require "nvar"
+
+Nvar.load_all
+```
+
 ## Configuration
 
 `Nvar` is configured by way of `config/environment_variables.yml`. If you're on Rails, this file will be created for you automatically. Each key corresponds to the name of a required environment variable, and houses its configuration, all of which is optional.

lib/nvar.rb

@@ -11,7 +11,7 @@
 module Nvar
   mattr_accessor :config_file_path, default: File.expand_path("config/environment_variables.yml")
   mattr_accessor :env_file_path, default: File.expand_path(".env")
-  mattr_accessor :env, default: :development
+  mattr_accessor :env
 
   # Comments in .env files must have a leading '#' symbol. This cannot be
   # followed by a space.
@@ -42,7 +42,11 @@ def message
 
   class << self
     def env
-      ActiveSupport::StringInquirer.new(@@env.to_s)
+      if defined?(Rails)
+        Rails.env
+      else
+        ActiveSupport::StringInquirer.new(@@env&.to_s || ENV["RAILS_ENV"] || ENV["RACK_ENV"] || "development")
+      end
     end
 
     def configure_for_rails(app)
@@ -51,6 +55,7 @@ def configure_for_rails(app)
       [config_file_path, env_file_path].each do |path|
         File.open(path, "w") {} unless path.exist? # rubocop:disable Lint/EmptyBlock
       end
+      self.env = Rails.env
     end
 
     def load_all

lib/nvar/environment_variable.rb

@@ -26,7 +26,7 @@ def initialize(name:, type: "String", filter_from_requests: nil, **args)
     def to_const
       raise Nvar::EnvironmentVariableNotPresentError, self unless defined
 
-      Object.const_set(name, typecast_value)
+      Object.const_set(name, typecast_value) unless Object.const_defined?(name)
     end
 
     def set?