Enable passthrough by specifying environment variable name in NVAR_PASSTHROUGH

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    nvar (0.2.0)
+    nvar (0.3.0)
       activesupport (>= 5.0.0, < 8.0)
 
 GEM
@@ -148,6 +148,7 @@ GEM
     parser (3.3.0.5)
       ast (~> 2.4.1)
       racc
+    prism (0.24.0)
     psych (5.1.2)
       stringio
     racc (1.7.3)
@@ -225,6 +226,12 @@ GEM
     rubocop-performance (1.20.2)
       rubocop (>= 1.48.1, < 2.0)
       rubocop-ast (>= 1.30.0, < 2.0)
+    ruby-lsp (0.14.3)
+      language_server-protocol (~> 3.17.0)
+      prism (>= 0.22.0, < 0.25)
+      sorbet-runtime (>= 0.5.10782)
+    ruby-lsp-rspec (0.1.10)
+      ruby-lsp (~> 0.14.0)
     ruby-progressbar (1.13.0)
     ruby2_keywords (0.0.5)
     simplecov (0.22.0)
@@ -233,6 +240,7 @@ GEM
       simplecov_json_formatter (~> 0.1)
     simplecov-html (0.12.3)
     simplecov_json_formatter (0.1.4)
+    sorbet-runtime (0.5.11276)
     standard (1.34.0)
       language_server-protocol (~> 3.17.0.2)
       lint_roller (~> 1.0)
@@ -277,6 +285,7 @@ DEPENDENCIES
   rails
   rake (~> 12.0)
   rspec (~> 3.0)
+  ruby-lsp-rspec
   simplecov
   standardrb
   tempfile

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.
@@ -36,7 +46,7 @@ This is just a glimpse of `Nvar`'s greater aim - centralizing configuration for
 
 ### Passthrough
 
-The final config option, `passthrough`, deserves some extra detail. By default, `Nvar` sets your environment constants to their actual values in development and production environments, and to their names in test environments.
+The final config option, `passthrough`, deserves some extra detail. By default, `Nvar` sets your environment constants to their actual values in development and production environments, and to their names in test environments, in order to prevent your tests from depending on their values.
 
 In production/development, or in test with passthrough active:
 
@@ -52,17 +62,20 @@ irb(main):001:0> REQUIRED_ENV_VAR
 => "REQUIRED_ENV_VAR"
 ```
 
-Your tests shouldn't be reliant on your environment, so generally, you want to have `passthrough` set to `true` as little as possible. What it *is* useful for, however, is recording VCR cassettes. Set `passthrough: true` on necessary environment variables before recording VCR cassettes, then remove it and run your tests again to make sure they're not reliant on your environment.
+Your tests shouldn't be reliant on your environment, so setting `passthrough` to `true` in `config/environment_variables.yml` isn't recommended. Passthrough is, however, useful for recording VCR cassettes. Set NVAR_PASSTHROUGH to a comma-separated list of environment variable names while running your tests, then unset it and run your tests again to make sure they're not reliant on your environment. For example:
 
+```
+NVAR_PASSTHROUGH=GITHUB_APP_PRIVATE_KEY,GITHUB_APP_INSTALLATION_ID bundle exec rspec
+```
 
 ## Usage
 
 Now that you've been through and configured the environment variables that are necessary for your app, `Nvar` will write your environment variables to top-level constants, cast to any types you've specified, and raise an informative error if any are absent.
 ### .env files
 
-`Nvar` works well with gems like `dotenv-rails` that source their config from a `.env` file. If an environment variable is unset when the app initializes and isn't present in `.env`, it will be added to that file. If a default value is specified in your `Nvar` config, that will be passed to `.env` too.
+`Nvar` works well with gems like `dotenv` that source their config from a `.env` file. If an environment variable is unset when the app initializes and isn't present in `.env`, it will be added to that file. If a default value is specified in your `Nvar` config, that will be passed to `.env` too.
 
-When using gems such as `dotenv-rails`, make sure you load those first so that the environment is ready for `Nvar` to check.
+When using gems such as `dotenv`, make sure you load those first so that the environment is ready for `Nvar` to check.
 
 ### `rake nvar:verify_environment_file`
 

lib/nvar.rb

@@ -4,11 +4,14 @@
 require "nvar/environment_variable"
 require "nvar/engine" if defined?(Rails)
 require "active_support/core_ext/module/attribute_accessors"
+require "active_support/core_ext/hash/reverse_merge"
+require "active_support/string_inquirer"
 
 # Centralized configuration for required environment variables in your Ruby app.
 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
 
   # Comments in .env files must have a leading '#' symbol. This cannot be
   # followed by a space.
@@ -38,12 +41,21 @@ def message
   end
 
   class << self
+    def env
+      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)
       self.config_file_path = app.root.join("config/environment_variables.yml")
       self.env_file_path = app.root.join(".env")
       [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
@@ -62,7 +74,6 @@ def filter_from_vcr_cassettes(config)
 
     def all
       variables.map do |variable_name, config|
-        # TODO: Passthrough from environment behaviour might need to go here?
         EnvironmentVariable.new(**(config || {}).merge(name: variable_name))
       end.partition(&:set?)
     end

lib/nvar/environment_variable.rb

@@ -16,7 +16,7 @@ def initialize(name:, type: "String", filter_from_requests: nil, **args)
       @type = type
       @required = args[:required].nil? ? true : args[:required]
       @filter_from_requests = filter_from_requests.yield_self { |f| [true, false].include?(f) ? f : f&.to_sym }
-      @value = fetch_value(**args.slice(:passthrough, :default_value))
+      @value = fetch_value(**args.slice(:passthrough, :default_value).with_defaults(passthrough: ENV.fetch("NVAR_PASSTHROUGH", "").split(",").include?(name.to_s)))
       @defined = true
     rescue KeyError
       @value = args[:default_value]
@@ -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?
@@ -76,7 +76,7 @@ def typecast_value
     end
 
     def fetch_value(passthrough: false, default_value: nil)
-      return default_value || name if ENV["RAILS_ENV"] == "test" && !passthrough
+      return default_value || name.to_s if Nvar.env.test? && !passthrough
 
       required ? ENV.fetch(name.to_s) : ENV[name.to_s]
     end

lib/nvar/version.rb

@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module Nvar
-  VERSION = "0.2.0"
+  VERSION = "0.3.0"
 end

nvar.gemspec

@@ -33,6 +33,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "byebug"
   spec.add_development_dependency "climate_control"
   spec.add_development_dependency "rails"
+  spec.add_development_dependency "ruby-lsp-rspec"
   spec.add_development_dependency "simplecov"
   spec.add_development_dependency "standardrb"
   spec.add_development_dependency "tempfile"