Rails.env falls back to dev mode when env var is empty

railties/CHANGELOG.md

+*   Make `Rails.env` fall back to `development` when `RAILS_ENV` and `RACK_ENV` is an empty string.
+
+   *Daniel Deng*
+
 *   Add Webpack support in new apps via the --webpack option, which will delegate to the rails/webpacker gem.
 
     To generate a new app that has Webpack dependencies configured and binstubs for webpack and webpack-watcher:

railties/lib/rails.rb

@@ -7,6 +7,7 @@
 require "active_support/core_ext/kernel/reporting"
 require "active_support/core_ext/module/delegation"
 require "active_support/core_ext/array/extract_options"
+require "active_support/core_ext/object/blank"
 
 require "rails/application"
 require "rails/version"
@@ -67,7 +68,7 @@ def root
     #   Rails.env.development? # => true
     #   Rails.env.production? # => false
     def env
-      @_env ||= ActiveSupport::StringInquirer.new(ENV["RAILS_ENV"] || ENV["RACK_ENV"] || "development")
+      @_env ||= ActiveSupport::StringInquirer.new(ENV["RAILS_ENV"].presence || ENV["RACK_ENV"].presence || "development")
     end
 
     # Sets the Rails environment.

railties/test/application/configuration_test.rb

@@ -78,6 +78,18 @@ def restore_default_config
       end
     end
 
+    test "Rails.env falls back to development if RAILS_ENV is blank and RACK_ENV is nil" do
+      with_rails_env("") do
+        assert_equal "development", Rails.env
+      end
+    end
+
+    test "Rails.env falls back to development if RACK_ENV is blank and RAILS_ENV is nil" do
+      with_rack_env("") do
+        assert_equal "development", Rails.env
+      end
+    end
+
     test "By default logs tags are not set in development" do
       restore_default_config