Rename Ruby::Enum to RubyEnum::Enum

Ruby 4.0 reserves the top-level Ruby module for the language itself,
so reopening 'module Ruby' in this gem is no longer safe. Renames the
gem's namespace from Ruby::Enum to RubyEnum::Enum and bumps the major
version to 2.0.0.

For backward compatibility, Ruby::Enum (and Ruby::Enum::Case,
Ruby::Enum::Errors) remain available as deprecated aliases that warn
on inclusion and delegate to RubyEnum::Enum. They will be removed in
a future major version.

Closes #55.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: dblock

CHANGELOG.md

@@ -1,5 +1,6 @@
-### 1.2.0 (Next)
+### 2.0.0 (Next)
 
+* [#55](https://github.com/dblock/ruby-enum/issues/55): Renamed `Ruby::Enum` to `RubyEnum::Enum` since Ruby 4.0 reserves the top-level `Ruby` module - [@dblock](https://github.com/dblock).
 * Your contribution here.
 
 ### 1.1.0 (2026/6/20)

README.md

@@ -1,4 +1,4 @@
-Ruby::Enum
+RubyEnum::Enum
 ==========
 
 [![Gem Version](http://img.shields.io/gem/v/ruby-enum.svg)](http://badge.fury.io/rb/ruby-enum)
@@ -41,7 +41,7 @@ Define enums, and reference them as constants.
 
 ``` ruby
 class OrderState
-  include Ruby::Enum
+  include RubyEnum::Enum
 
   define :CREATED, 'created'
   define :PAID, 'paid'
@@ -51,7 +51,7 @@ end
 ``` ruby
 OrderState::CREATED # 'created'
 OrderState::PAID # 'paid'
-OrderState::UNKNOWN # raises Ruby::Enum::Errors::UninitializedConstantError
+OrderState::UNKNOWN # raises RubyEnum::Enum::Errors::UninitializedConstantError
 OrderState.keys # [ :CREATED, :PAID ]
 OrderState.values # [ 'created', 'paid' ]
 OrderState.to_h # { :CREATED => 'created', :PAID => 'paid' }
@@ -63,7 +63,7 @@ Define enums, and reference them as class methods.
 
 ``` ruby
 class OrderState
-  include Ruby::Enum
+  include RubyEnum::Enum
 
   define :created, 'created'
   define :paid, 'paid'
@@ -85,7 +85,7 @@ The value is optional. If unspecified, the value will default to the key.
 
 ``` ruby
 class OrderState
-  include Ruby::Enum
+  include RubyEnum::Enum
 
   define :UNSPECIFIED
   define :unspecified
@@ -206,22 +206,22 @@ OrderState.key('failed')
 
 ### Duplicate enumerator keys or duplicate values
 
-Defining duplicate enums raises `Ruby::Enum::Errors::DuplicateKeyError`.
+Defining duplicate enums raises `RubyEnum::Enum::Errors::DuplicateKeyError`.
 
 ```ruby
 class OrderState
-  include Ruby::Enum
+  include RubyEnum::Enum
 
   define :CREATED, 'created'
   define :CREATED, 'recreated' # raises DuplicateKeyError
 end
 ```
 
-Defining a duplicate value raises `Ruby::Enum::Errors::DuplicateValueError`.
+Defining a duplicate value raises `RubyEnum::Enum::Errors::DuplicateValueError`.
 
 ```ruby
 class OrderState
-  include Ruby::Enum
+  include RubyEnum::Enum
 
   define :CREATED, 'created'
   define :RECREATED, 'created' # raises DuplicateValueError
@@ -232,11 +232,11 @@ The `DuplicateValueError` exception is raised to be consistent with the unique k
 
 ### Inheritance
 
-When inheriting from a `Ruby::Enum` class, all defined enums in the parent class will be accessible in sub classes as well. Sub classes can also provide extra enums, as usual.
+When inheriting from a `RubyEnum::Enum` class, all defined enums in the parent class will be accessible in sub classes as well. Sub classes can also provide extra enums, as usual.
 
 ``` ruby
 class OrderState
-  include Ruby::Enum
+  include RubyEnum::Enum
 
   define :CREATED, 'CREATED'
   define :PAID, 'PAID'
@@ -264,16 +264,16 @@ ShippedOrderState.values # ['CREATED', 'PAID', 'PREPARED', SHIPPED']
 
 ### Exhaustive case matcher
 
-If you want to make sure that you cover all cases in a case stament, you can use the exhaustive case matcher: `Ruby::Enum::Case`. It will raise an error if a case/enum value is not handled, or if a value is specified that's not part of the enum. This is inspired by the [Rust Pattern Syntax](https://doc.rust-lang.org/book/ch18-03-pattern-syntax.html). If multiple cases match, all matches are being executed. The return value is the value from the matched case, or an array of return values if multiple cases matched.
+If you want to make sure that you cover all cases in a case stament, you can use the exhaustive case matcher: `RubyEnum::Enum::Case`. It will raise an error if a case/enum value is not handled, or if a value is specified that's not part of the enum. This is inspired by the [Rust Pattern Syntax](https://doc.rust-lang.org/book/ch18-03-pattern-syntax.html). If multiple cases match, all matches are being executed. The return value is the value from the matched case, or an array of return values if multiple cases matched.
 
 > NOTE: This will add checks at runtime which might lead to worse performance. See [benchmarks](#benchmarks).
 
-> NOTE: `:else` is a reserved keyword if you want to use `Ruby::Enum::Case`.
+> NOTE: `:else` is a reserved keyword if you want to use `RubyEnum::Enum::Case`.
 
 ```ruby
 class Color < OrderState
-  include Ruby::Enum
-  include Ruby::Enum::Case
+  include RubyEnum::Enum
+  include RubyEnum::Enum::Case
 
   define :RED, :red
   define :GREEN, :green

UPGRADING.md

@@ -1,10 +1,45 @@
-# Upgrading Ruby::Enum
+# Upgrading RubyEnum::Enum
+
+## Upgrading to >= 2.0.0
+
+### Module renamed from `Ruby::Enum` to `RubyEnum::Enum`
+
+Ruby 4.0 reserves the top-level `Ruby` module for the language itself, so this
+gem's `Ruby::Enum` namespace is no longer safe to use. As of `2.0.0`, the gem
+uses `RubyEnum::Enum` instead.
+
+`gem 'ruby-enum', '< 2.0.0'`
+
+``` ruby
+class Color
+  include Ruby::Enum
+
+  define :RED, 'red'
+end
+```
+
+`gem 'ruby-enum', '>= 2.0.0'`
+
+``` ruby
+class Color
+  include RubyEnum::Enum
+
+  define :RED, 'red'
+end
+```
+
+For backward compatibility, `Ruby::Enum` is still available as a deprecated
+alias for `RubyEnum::Enum` and will emit a deprecation warning when included.
+It will be removed in a future major version. Update your code to use
+`RubyEnum::Enum` and `RubyEnum::Enum::Case` directly.
+
+See [#55](https://github.com/dblock/ruby-enum/issues/55) for more information.
 
 ## Upgrading to >= 0.9.0
 
-### Inheritance & `Ruby::Enum.values`
+### Inheritance & `RubyEnum::Enum.values`
 
-This only applies to classes that inherit from another which is a `Ruby::Enum`.
+This only applies to classes that inherit from another which is a `RubyEnum::Enum`.
 
 Prior to version `0.9.0`, the `values` class method would enumerate only the
 values defined in the class.
@@ -14,7 +49,7 @@ the entire class heirarchy, ancestors first.
 
 ``` ruby
 class PrimaryColors
-  include Ruby::Enum
+  include RubyEnum::Enum
 
   define :RED, 'RED'
   define :GREEN, 'GREEN'

benchmarks/case.rb

@@ -8,8 +8,8 @@
 ##
 # Test enum
 class Color
-  include Ruby::Enum
-  include Ruby::Enum::Case
+  include RubyEnum::Enum
+  include RubyEnum::Enum::Case
 
   define :RED, :red
   define :GREEN, :green

lib/config/locales/en.yml

@@ -9,7 +9,7 @@ en:
             resolution: "The enumerated value could not be found in class %{name}. Use 'define' to declare it.\n
             \_Example:\n
             \_\_module %{name}\n
-            \_\_\_include Ruby::Enum\n
+            \_\_\_include RubyEnum::Enum\n
             \_\_\_define %{key}, 'value'\n
             \_\_end"
           duplicate_key:

lib/ruby-enum.rb

@@ -8,18 +8,19 @@
 # Try to load the I18n gem and provide a mock if it is not available.
 begin
   require 'i18n'
-  Ruby::Enum.i18n = I18n
+  RubyEnum::Enum.i18n = I18n
 rescue LoadError
   # I18n is not available
   # :nocov:
   # Tests for this loading are in the spec_i18n folder
-  Ruby::Enum.i18n = Ruby::Enum::I18nMock
+  RubyEnum::Enum.i18n = RubyEnum::Enum::I18nMock
   # :nocov:
 end
 
-Ruby::Enum.i18n.load_path << File.join(File.dirname(__FILE__), 'config', 'locales', 'en.yml')
+RubyEnum::Enum.i18n.load_path << File.join(File.dirname(__FILE__), 'config', 'locales', 'en.yml')
 
 require 'ruby-enum/errors/base'
 require 'ruby-enum/errors/uninitialized_constant_error'
 require 'ruby-enum/errors/duplicate_key_error'
 require 'ruby-enum/errors/duplicate_value_error'
+require 'ruby-enum/deprecated'

lib/ruby-enum/deprecated.rb

@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+# Deprecated backward-compatible alias for RubyEnum::Enum.
+#
+# Ruby 4.0 reserves the top-level `Ruby` module for the language itself, so
+# this namespace is deprecated and will be removed in a future major version.
+# Use RubyEnum::Enum instead.
+module Ruby
+  module Enum
+    def self.included(base)
+      warn '[DEPRECATION] `Ruby::Enum` is deprecated and will be removed in a future version. ' \
+           'Use `RubyEnum::Enum` instead.'
+
+      base.include RubyEnum::Enum
+    end
+
+    module Case
+      def self.included(base)
+        warn '[DEPRECATION] `Ruby::Enum::Case` is deprecated and will be removed in a future version. ' \
+             'Use `RubyEnum::Enum::Case` instead.'
+
+        base.include RubyEnum::Enum::Case
+      end
+    end
+
+    Errors = RubyEnum::Enum::Errors
+  end
+end

lib/ruby-enum/enum.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-module Ruby
+module RubyEnum
   module Enum
     class << self
       # Needed for I18n mock
@@ -53,7 +53,7 @@ def store_new_instance(key, value)
       end
 
       def const_missing(key)
-        raise Ruby::Enum::Errors::UninitializedConstantError, name: name, key: key
+        raise RubyEnum::Enum::Errors::UninitializedConstantError, name: name, key: key
       end
 
       # Iterate over all enumerated values.
@@ -128,7 +128,7 @@ def keys
       def values
         result = @_enum_hash.values.map(&:value)
 
-        if superclass < Ruby::Enum
+        if superclass < RubyEnum::Enum
           superclass.values + result
         else
           result
@@ -164,13 +164,13 @@ def upper?(s)
       def validate_key!(key)
         return unless @_enum_hash.key?(key)
 
-        raise Ruby::Enum::Errors::DuplicateKeyError, name: name, key: key
+        raise RubyEnum::Enum::Errors::DuplicateKeyError, name: name, key: key
       end
 
       def validate_value!(value)
         return unless @_enums_by_value.key?(value)
 
-        raise Ruby::Enum::Errors::DuplicateValueError, name: name, value: value
+        raise RubyEnum::Enum::Errors::DuplicateValueError, name: name, value: value
       end
     end
   end

lib/ruby-enum/enum/case.rb

@@ -1,14 +1,14 @@
 # frozen_string_literal: true
 
-module Ruby
+module RubyEnum
   module Enum
     ##
     # Adds a method to an enum class that allows for exhaustive matching on a value.
     #
     # @example
     # class Color
-    #   include Ruby::Enum
-    #   include Ruby::Enum::Case
+    #   include RubyEnum::Enum
+    #   include RubyEnum::Enum::Case
     #
     #   define :RED, :red
     #   define :GREEN, :green
@@ -33,7 +33,7 @@ def self.included(klass)
       end
 
       ##
-      # @see Ruby::Enum::Case
+      # @see RubyEnum::Enum::Case
       module ClassMethods
         class ValuesNotDefinedError < StandardError
         end

lib/ruby-enum/enum/i18n_mock.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 # :nocov:
-module Ruby
+module RubyEnum
   module Enum
     ##
     # Mock I18n module in case the i18n gem is not available.