From b538ce73616d3a1e91aee291fca3fafc352bfe95 Mon Sep 17 00:00:00 2001
From: Rylan Polster <rslpolster@gmail.com>
Date: Thu, 23 Jun 2022 17:18:58 -0400
Subject: [PATCH 01/10] Add `OnSystem` module to generate `on_*` methods for
 formulae and casks

---
 Library/Homebrew/cask/dsl.rb              |  20 ++++-
 Library/Homebrew/extend/on_os.rb          |  26 ------
 Library/Homebrew/extend/on_os.rbi         |   5 --
 Library/Homebrew/extend/on_system.rb      | 105 ++++++++++++++++++++++
 Library/Homebrew/extend/os/linux/on_os.rb |  10 ---
 Library/Homebrew/extend/os/mac/on_os.rb   |  10 ---
 Library/Homebrew/extend/os/on_os.rb       |   8 --
 Library/Homebrew/formula.rb               |   8 +-
 Library/Homebrew/formula.rbi              |   3 +
 Library/Homebrew/override.rb              |  53 +++++++++++
 Library/Homebrew/resource.rb              |   5 +-
 Library/Homebrew/software_spec.rb         |   7 +-
 12 files changed, 191 insertions(+), 69 deletions(-)
 delete mode 100644 Library/Homebrew/extend/on_os.rb
 delete mode 100644 Library/Homebrew/extend/on_os.rbi
 create mode 100644 Library/Homebrew/extend/on_system.rb
 delete mode 100644 Library/Homebrew/extend/os/linux/on_os.rb
 delete mode 100644 Library/Homebrew/extend/os/mac/on_os.rb
 delete mode 100644 Library/Homebrew/extend/os/on_os.rb
 create mode 100644 Library/Homebrew/override.rb

diff --git a/Library/Homebrew/cask/dsl.rb b/Library/Homebrew/cask/dsl.rb
index e4d1ac47a2..9a631484d1 100644
--- a/Library/Homebrew/cask/dsl.rb
+++ b/Library/Homebrew/cask/dsl.rb
@@ -4,6 +4,7 @@
 require "locale"
 require "lazy_object"
 require "livecheck"
+require "override"
 
 require "cask/artifact"
 
@@ -25,6 +26,8 @@ require "cask/dsl/version"
 require "cask/url"
 require "cask/utils"
 
+require "extend/on_system"
+
 module Cask
   # Class representing the domain-specific language used for casks.
   #
@@ -89,8 +92,12 @@ module Cask
       *ARTIFACT_BLOCK_CLASSES.flat_map { |klass| [klass.dsl_key, klass.uninstall_dsl_key] },
     ]).freeze
 
+    extend Predicable
+
     attr_reader :cask, :token
 
+    attr_predicate :on_system_blocks_exist?
+
     def initialize(cask)
       @cask = cask
       @token = cask.token
@@ -112,10 +119,17 @@ module Cask
     def set_unique_stanza(stanza, should_return)
       return instance_variable_get("@#{stanza}") if should_return
 
-      if !@cask.allow_reassignment && instance_variable_defined?("@#{stanza}")
-        raise CaskInvalidError.new(cask, "'#{stanza}' stanza may only appear once.")
+      unless @cask.allow_reassignment
+        if instance_variable_defined?("@#{stanza}") && !@called_in_on_system_block
+          raise CaskInvalidError.new(cask, "'#{stanza}' stanza may only appear once.")
+        end
+
+        if instance_variable_defined?("@#{stanza}_set_in_block") && @called_in_on_system_block
+          raise CaskInvalidError.new(cask, "'#{stanza}' stanza may only be overridden once.")
+        end
       end
 
+      instance_variable_set("@#{stanza}_set_in_block", true) if @called_in_on_system_block
       instance_variable_set("@#{stanza}", yield)
     rescue CaskInvalidError
       raise
@@ -306,6 +320,8 @@ module Cask
       @livecheckable == true
     end
 
+    OnSystem.setup_methods! onto: self, include_linux: false
+
     ORDINARY_ARTIFACT_CLASSES.each do |klass|
       define_method(klass.dsl_key) do |*args|
         if [*artifacts.map(&:class), klass].include?(Artifact::StageOnly) &&
diff --git a/Library/Homebrew/extend/on_os.rb b/Library/Homebrew/extend/on_os.rb
deleted file mode 100644
index aacadd608e..0000000000
--- a/Library/Homebrew/extend/on_os.rb
+++ /dev/null
@@ -1,26 +0,0 @@
-# typed: strict
-# frozen_string_literal: true
-
-module OnOS
-  extend T::Sig
-
-  # Block only executed on macOS. No-op on Linux.
-  # <pre>on_macos do
-  # # Do something Mac-specific
-  # end</pre>
-  sig { params(block: T.proc.void).void }
-  def on_macos(&block)
-    raise "No block content defined for 'on_macos' block" unless T.unsafe(block)
-  end
-
-  # Block only executed on Linux. No-op on macOS.
-  # <pre>on_linux do
-  # # Do something Linux-specific
-  # end</pre>
-  sig { params(block: T.proc.void).void }
-  def on_linux(&block)
-    raise "No block content defined for 'on_linux' block" unless T.unsafe(block)
-  end
-end
-
-require "extend/os/on_os"
diff --git a/Library/Homebrew/extend/on_os.rbi b/Library/Homebrew/extend/on_os.rbi
deleted file mode 100644
index a53474fd86..0000000000
--- a/Library/Homebrew/extend/on_os.rbi
+++ /dev/null
@@ -1,5 +0,0 @@
-# typed: strict
-
-module OnOS
-  include Kernel
-end
diff --git a/Library/Homebrew/extend/on_system.rb b/Library/Homebrew/extend/on_system.rb
new file mode 100644
index 0000000000..711bb4b187
--- /dev/null
+++ b/Library/Homebrew/extend/on_system.rb
@@ -0,0 +1,105 @@
+# typed: false
+# frozen_string_literal: true
+
+require "override"
+
+module OnSystem
+  extend T::Sig
+
+  ARCH_OPTIONS = [:intel, :arm].freeze
+  BASE_OS_OPTIONS = [:macos, :linux].freeze
+
+  module_function
+
+  sig { params(arch: Symbol).returns(T::Boolean) }
+  def arch_condition_met?(arch)
+    raise ArgumentError, "Invalid arch condition: #{arch.inspect}" unless ARCH_OPTIONS.include?(arch)
+
+    current_arch = Homebrew::Override.arch || Hardware::CPU.type
+    arch == current_arch
+  end
+
+  sig { params(os_name: Symbol, or_condition: T.nilable(Symbol)).returns(T::Boolean) }
+  def os_condition_met?(os_name, or_condition = nil)
+    if Homebrew::EnvConfig.simulate_macos_on_linux?
+      return false if os_name == :linux
+      return true if [:macos, *MacOS::Version::SYMBOLS.keys].include?(os_name)
+    end
+
+    if BASE_OS_OPTIONS.include?(os_name)
+      if Homebrew::Override.none?
+        return OS.linux? if os_name == :linux
+        return OS.mac? if os_name == :macos
+      end
+
+      return Homebrew::Override.send("#{os_name}?")
+    end
+
+    raise ArgumentError, "Invalid OS condition: #{os_name.inspect}" unless MacOS::Version::SYMBOLS.key?(os_name)
+
+    if or_condition.present? && [:or_newer, :or_older].exclude?(or_condition)
+      raise ArgumentError, "Invalid OS `or_*` condition: #{or_condition.inspect}"
+    end
+
+    base_os = MacOS::Version.from_symbol(os_name)
+    current_os = MacOS::Version.from_symbol(Homebrew::Override.os || MacOS.version.to_sym)
+
+    return current_os >= base_os if or_condition == :or_newer
+    return current_os <= base_os if or_condition == :or_older
+
+    current_os == base_os
+  end
+
+  sig { params(method_name: Symbol).returns(Symbol) }
+  def condition_from_method_name(method_name)
+    method_name.to_s.sub(/^on_/, "").to_sym
+  end
+
+  sig { params(onto: Class, include_linux: T::Boolean).void }
+  def setup_methods!(onto:, include_linux: true)
+    ARCH_OPTIONS.each do |arch|
+      onto.define_method("on_#{arch}") do |&block|
+        @on_system_blocks_exist = true
+
+        return unless OnSystem.arch_condition_met? OnSystem.condition_from_method_name(__method__)
+
+        @called_in_on_system_block = true
+        result = block.call
+        @called_in_on_system_block = false
+
+        result
+      end
+    end
+
+    if include_linux
+      BASE_OS_OPTIONS.each do |base_os|
+        onto.define_method("on_#{base_os}") do |&block|
+          @on_system_blocks_exist = true
+
+          return unless OnSystem.os_condition_met? OnSystem.condition_from_method_name(__method__)
+
+          @called_in_on_system_block = true
+          result = block.call
+          @called_in_on_system_block = false
+
+          result
+        end
+      end
+    end
+
+    MacOS::Version::SYMBOLS.each_key do |os_name|
+      onto.define_method("on_#{os_name}") do |or_condition = nil, &block|
+        @on_system_blocks_exist = true
+
+        os_condition = OnSystem.condition_from_method_name __method__
+        return unless OnSystem.os_condition_met? os_condition, or_condition
+
+        @called_in_on_system_block = true
+        result = block.call
+        @called_in_on_system_block = false
+
+        result
+      end
+    end
+  end
+end
diff --git a/Library/Homebrew/extend/os/linux/on_os.rb b/Library/Homebrew/extend/os/linux/on_os.rb
deleted file mode 100644
index 4373a45ab2..0000000000
--- a/Library/Homebrew/extend/os/linux/on_os.rb
+++ /dev/null
@@ -1,10 +0,0 @@
-# typed: strict
-# frozen_string_literal: true
-
-module OnOS
-  def on_linux(&block)
-    raise "No block content defined for 'on_linux' block" unless T.unsafe(block)
-
-    yield
-  end
-end
diff --git a/Library/Homebrew/extend/os/mac/on_os.rb b/Library/Homebrew/extend/os/mac/on_os.rb
deleted file mode 100644
index 78759c1a9d..0000000000
--- a/Library/Homebrew/extend/os/mac/on_os.rb
+++ /dev/null
@@ -1,10 +0,0 @@
-# typed: strict
-# frozen_string_literal: true
-
-module OnOS
-  def on_macos(&block)
-    raise "No block content defined for 'on_macos' block" unless T.unsafe(block)
-
-    yield
-  end
-end
diff --git a/Library/Homebrew/extend/os/on_os.rb b/Library/Homebrew/extend/os/on_os.rb
deleted file mode 100644
index c74ea9d459..0000000000
--- a/Library/Homebrew/extend/os/on_os.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-# typed: strict
-# frozen_string_literal: true
-
-if OS.mac? || Homebrew::EnvConfig.simulate_macos_on_linux?
-  require "extend/os/mac/on_os"
-elsif OS.linux?
-  require "extend/os/linux/on_os"
-end
diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index 25ff2c3920..250583b465 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -28,7 +28,7 @@ require "tab"
 require "mktemp"
 require "find"
 require "utils/spdx"
-require "extend/on_os"
+require "extend/on_system"
 require "api"
 
 # A formula provides instructions and metadata for Homebrew to install a piece
@@ -64,11 +64,12 @@ class Formula
   include Utils::Shebang
   include Utils::Shell
   include Context
-  include OnOS
   extend Forwardable
   extend Cachable
   extend Predicable
 
+  OnSystem.setup_methods! onto: self
+
   # @!method inreplace(paths, before = nil, after = nil)
   # @see Utils::Inreplace.inreplace
 
@@ -2470,7 +2471,6 @@ class Formula
   # The methods below define the formula DSL.
   class << self
     include BuildEnvironment::DSL
-    include OnOS
 
     def method_added(method)
       super
@@ -2483,6 +2483,8 @@ class Formula
       end
     end
 
+    OnSystem.setup_methods! onto: self
+
     # The reason for why this software is not linked (by default) to
     # {::HOMEBREW_PREFIX}.
     # @private
diff --git a/Library/Homebrew/formula.rbi b/Library/Homebrew/formula.rbi
index c573f64b3c..a47b034dee 100644
--- a/Library/Homebrew/formula.rbi
+++ b/Library/Homebrew/formula.rbi
@@ -48,4 +48,7 @@ class Formula
 
   def env; end
   def conflicts; end
+
+  # This method is generated by `OnSystem::setup_methods!`
+  def self.on_macos(&block); end
 end
diff --git a/Library/Homebrew/override.rb b/Library/Homebrew/override.rb
new file mode 100644
index 0000000000..7b6765ac5d
--- /dev/null
+++ b/Library/Homebrew/override.rb
@@ -0,0 +1,53 @@
+# typed: true
+# frozen_string_literal: true
+
+module Homebrew
+  # Helper module for overriding machine-specific methods.
+  #
+  # @api private
+  class Override
+    class << self
+      extend T::Sig
+
+      ARCH_OPTIONS = [:intel, :arm64].freeze
+      OS_OPTIONS = [:macos, :linux].freeze
+
+      attr_reader :os, :arch
+
+      sig { params(new_os: Symbol).void }
+      def os=(new_os)
+        os_options = [:macos, :linux, *MacOS::Version::SYMBOLS.keys]
+        raise "Unknown OS: #{new_os}" unless os_options.include?(new_os)
+
+        @os = new_os
+      end
+
+      sig { params(new_arch: Symbol).void }
+      def arch=(new_arch)
+        raise "New arch must be :arm or :intel" unless [:arm, :intel].include?(new_arch)
+
+        @arch = new_arch
+      end
+
+      sig { void }
+      def clear
+        @os = @arch = nil
+      end
+
+      sig { returns(T::Boolean) }
+      def none?
+        @os.nil? && @arch.nil?
+      end
+
+      sig { returns(T::Boolean) }
+      def macos?
+        [:macos, *MacOS::Version::SYMBOLS.keys].include?(@os)
+      end
+
+      sig { returns(T::Boolean) }
+      def linux?
+        @os == :linux
+      end
+    end
+  end
+end
diff --git a/Library/Homebrew/resource.rb b/Library/Homebrew/resource.rb
index 49d9e362a8..9cbd64bc7f 100644
--- a/Library/Homebrew/resource.rb
+++ b/Library/Homebrew/resource.rb
@@ -5,7 +5,7 @@ require "download_strategy"
 require "checksum"
 require "version"
 require "mktemp"
-require "extend/on_os"
+require "extend/on_system"
 
 # Resource is the fundamental representation of an external resource. The
 # primary formula download, along with other declared resources, are instances
@@ -17,7 +17,8 @@ class Resource
 
   include Context
   include FileUtils
-  include OnOS
+
+  OnSystem.setup_methods! onto: self
 
   attr_reader :mirrors, :specs, :using, :source_modified_time, :patches, :owner
   attr_writer :version
diff --git a/Library/Homebrew/software_spec.rb b/Library/Homebrew/software_spec.rb
index 437af9f0a8..61a0b8d463 100644
--- a/Library/Homebrew/software_spec.rb
+++ b/Library/Homebrew/software_spec.rb
@@ -12,19 +12,20 @@ require "utils/bottles"
 require "patch"
 require "compilers"
 require "os/mac/version"
-require "extend/on_os"
+require "extend/on_system"
 
 class SoftwareSpec
   extend T::Sig
 
   extend Forwardable
-  include OnOS
 
   PREDEFINED_OPTIONS = {
     universal: Option.new("universal", "Build a universal binary"),
     cxx11:     Option.new("c++11",     "Build using C++11 mode"),
   }.freeze
 
+  OnSystem.setup_methods! onto: self
+
   attr_reader :name, :full_name, :owner, :build, :resources, :patches, :options, :deprecated_flags,
               :deprecated_options, :dependency_collector, :bottle_specification, :compiler_failures,
               :uses_from_macos_elements
@@ -583,7 +584,7 @@ class BottleSpecification
 end
 
 class PourBottleCheck
-  include OnOS
+  OnSystem.setup_methods! onto: self
 
   def initialize(formula)
     @formula = formula

From d3c3f7be9efbb697f07587c1b675948da67c13d7 Mon Sep 17 00:00:00 2001
From: Rylan Polster <rslpolster@gmail.com>
Date: Thu, 23 Jun 2022 17:19:27 -0400
Subject: [PATCH 02/10] Add `variations` to `Cask#to_h`

---
 Library/Homebrew/cask/cask.rb | 43 ++++++++++++++++++++++++++++++++++-
 1 file changed, 42 insertions(+), 1 deletion(-)

diff --git a/Library/Homebrew/cask/cask.rb b/Library/Homebrew/cask/cask.rb
index 89a7c19ad9..40218642e5 100644
--- a/Library/Homebrew/cask/cask.rb
+++ b/Library/Homebrew/cask/cask.rb
@@ -6,6 +6,7 @@ require "cask/config"
 require "cask/dsl"
 require "cask/metadata"
 require "searchable"
+require "utils/bottles"
 
 module Cask
   # An instance of a cask.
@@ -58,6 +59,10 @@ module Cask
     def config=(config)
       @config = config
 
+      refresh
+    end
+
+    def refresh
       @dsl = DSL.new(self)
       return unless @block
 
@@ -214,7 +219,7 @@ module Cask
     end
     alias == eql?
 
-    def to_h
+    def to_hash
       {
         "token"          => token,
         "full_token"     => full_name,
@@ -238,6 +243,42 @@ module Cask
       }
     end
 
+    def to_h
+      hash = to_hash
+      variations = {}
+
+      hash_keys_to_skip = %w[outdated installed versions]
+
+      if @dsl.on_system_blocks_exist?
+        [:arm, :intel].each do |arch|
+          MacOS::Version::SYMBOLS.each_key do |os_name|
+            # Big Sur is the first version of macOS that supports arm
+            next if arch == :arm && MacOS::Version.from_symbol(os_name) < MacOS::Version.from_symbol(:big_sur)
+
+            Homebrew::Override.os = os_name
+            Homebrew::Override.arch = arch
+
+            refresh
+
+            bottle_tag = ::Utils::Bottles::Tag.new(system: os_name, arch: arch).to_sym
+            to_hash.each do |key, value|
+              next if hash_keys_to_skip.include? key
+              next if value.to_s == hash[key].to_s
+
+              variations[bottle_tag] ||= {}
+              variations[bottle_tag][key] = value
+            end
+          end
+        end
+      end
+
+      Homebrew::Override.clear
+      refresh
+
+      hash["variations"] = variations
+      hash
+    end
+
     private
 
     def to_h_string_gsubs(string)

From 6ebd5174d6cb38035280b661b05aaaeec2bc9ca9 Mon Sep 17 00:00:00 2001
From: Rylan Polster <rslpolster@gmail.com>
Date: Thu, 23 Jun 2022 17:19:47 -0400
Subject: [PATCH 03/10] Update tests for `on_*` methods in formulae and casks

---
 Library/Homebrew/test/cask/cmd/list_spec.rb   |  59 +++++++--
 Library/Homebrew/test/formula_spec.rb         | 113 ++++++++++++++++++
 .../fixtures/cask/Casks/multiple-versions.rb  |  23 +++-
 3 files changed, 180 insertions(+), 15 deletions(-)

diff --git a/Library/Homebrew/test/cask/cmd/list_spec.rb b/Library/Homebrew/test/cask/cmd/list_spec.rb
index 81f7a83c8e..8149e76210 100644
--- a/Library/Homebrew/test/cask/cmd/list_spec.rb
+++ b/Library/Homebrew/test/cask/cmd/list_spec.rb
@@ -120,7 +120,9 @@ describe Cask::Cmd::List, :cask do
             },
             "conflicts_with": null,
             "container": null,
-            "auto_updates": null
+            "auto_updates": null,
+            "variations": {
+            }
           },
           {
             "token": "local-transmission",
@@ -149,7 +151,9 @@ describe Cask::Cmd::List, :cask do
             },
             "conflicts_with": null,
             "container": null,
-            "auto_updates": null
+            "auto_updates": null,
+            "variations": {
+            }
           },
           {
             "token": "multiple-versions",
@@ -160,11 +164,13 @@ describe Cask::Cmd::List, :cask do
             ],
             "desc": null,
             "homepage": "https://brew.sh/",
-            "url": "file://#{TEST_FIXTURE_DIR}/cask/caffeine.zip",
+            "url": "file://#{TEST_FIXTURE_DIR}/cask/caffeine/1.2.3/arm.zip",
             "appcast": null,
             "version": "1.2.3",
             "versions": {
-              "test_os": "1.2.0"
+              "big_sur": "1.2.0",
+              "catalina": "1.0.0",
+              "mojave": "1.0.0"
             },
             "installed": "1.2.3",
             "outdated": false,
@@ -179,7 +185,32 @@ describe Cask::Cmd::List, :cask do
             },
             "conflicts_with": null,
             "container": null,
-            "auto_updates": null
+            "auto_updates": null,
+            "variations": {
+              "arm_big_sur": {
+                "url": "file://#{TEST_FIXTURE_DIR}/cask/caffeine/1.2.0/arm.zip",
+                "version": "1.2.0",
+                "sha256": "8c62a2b791cf5f0da6066a0a4b6e85f62949cd60975da062df44adf887f4370b"
+              },
+              "intel_monterey": {
+                "url": "file://#{TEST_FIXTURE_DIR}/cask/caffeine/1.2.3/intel.zip"
+              },
+              "intel_big_sur": {
+                "url": "file://#{TEST_FIXTURE_DIR}/cask/caffeine/1.2.0/intel.zip",
+                "version": "1.2.0",
+                "sha256": "8c62a2b791cf5f0da6066a0a4b6e85f62949cd60975da062df44adf887f4370b"
+              },
+              "intel_catalina": {
+                "url": "file://#{TEST_FIXTURE_DIR}/cask/caffeine/1.0.0/intel.zip",
+                "version": "1.0.0",
+                "sha256": "1866dfa833b123bb8fe7fa7185ebf24d28d300d0643d75798bc23730af734216"
+              },
+              "intel_mojave": {
+                "url": "file://#{TEST_FIXTURE_DIR}/cask/caffeine/1.0.0/intel.zip",
+                "version": "1.0.0",
+                "sha256": "1866dfa833b123bb8fe7fa7185ebf24d28d300d0643d75798bc23730af734216"
+              }
+            }
           },
           {
             "token": "third-party-cask",
@@ -208,7 +239,9 @@ describe Cask::Cmd::List, :cask do
             },
             "conflicts_with": null,
             "container": null,
-            "auto_updates": null
+            "auto_updates": null,
+            "variations": {
+            }
           }
         ]
       EOS
@@ -217,10 +250,18 @@ describe Cask::Cmd::List, :cask do
     before do
       casks.map(&Cask::CaskLoader.method(:load)).each(&InstallHelper.method(:install_with_caskfile))
 
-      # Add a test OS to ensure that all cask versions are listed regardless of OS.
-      symbols = MacOS::Version::SYMBOLS.dup
-      symbols[:test_os] = "10.9"
+      # Use a more limited symbols list to shorten the variations hash
+      symbols = {
+        monterey: "12",
+        big_sur:  "11",
+        catalina: "10.15",
+        mojave:   "10.14",
+      }
       stub_const("MacOS::Version::SYMBOLS", symbols)
+
+      # For consistency, always run on Monterey and ARM
+      MacOS.full_version = "12"
+      allow(Hardware::CPU).to receive(:type).and_return(:arm)
     end
 
     it "of all installed Casks" do
diff --git a/Library/Homebrew/test/formula_spec.rb b/Library/Homebrew/test/formula_spec.rb
index 8c5ee1b2f5..58d70fcc5c 100644
--- a/Library/Homebrew/test/formula_spec.rb
+++ b/Library/Homebrew/test/formula_spec.rb
@@ -1580,4 +1580,117 @@ describe Formula do
       expect(f.test).to eq(2)
     end
   end
+
+  describe "on_{os_version} blocks", :needs_macos do
+    before do
+      Homebrew::Override.os = :monterey
+    end
+
+    after do
+      Homebrew::Override.clear
+    end
+
+    let(:f) do
+      Class.new(Testball) do
+        @test = 0
+        attr_reader :test
+
+        def install
+          on_monterey :or_newer do
+            @test = 1
+          end
+          on_big_sur do
+            @test = 2
+          end
+          on_catalina :or_older do
+            @test = 3
+          end
+        end
+      end.new
+    end
+
+    it "only calls code within `on_monterey`" do
+      Homebrew::Override.os = :monterey
+      f.brew { f.install }
+      expect(f.test).to eq(1)
+    end
+
+    it "only calls code within `on_monterey :or_newer`" do
+      Homebrew::Override.os = :ventura
+      f.brew { f.install }
+      expect(f.test).to eq(1)
+    end
+
+    it "only calls code within `on_big_sur`" do
+      Homebrew::Override.os = :big_sur
+      f.brew { f.install }
+      expect(f.test).to eq(2)
+    end
+
+    it "only calls code within `on_catalina`" do
+      Homebrew::Override.os = :catalina
+      f.brew { f.install }
+      expect(f.test).to eq(3)
+    end
+
+    it "only calls code within `on_catalina :or_older`" do
+      Homebrew::Override.os = :mojave
+      f.brew { f.install }
+      expect(f.test).to eq(3)
+    end
+  end
+
+  describe "#on_arm" do
+    before do
+      allow(Hardware::CPU).to receive(:type).and_return(:arm)
+    end
+
+    let(:f) do
+      Class.new(Testball) do
+        @test = 0
+        attr_reader :test
+
+        def install
+          on_arm do
+            @test = 1
+          end
+          on_intel do
+            @test = 2
+          end
+        end
+      end.new
+    end
+
+    it "only calls code within on_arm" do
+      f.brew { f.install }
+      expect(f.test).to eq(1)
+    end
+  end
+
+  describe "#on_intel" do
+    before do
+      allow(Hardware::CPU).to receive(:type).and_return(:intel)
+    end
+
+    let(:f) do
+      Class.new(Testball) do
+        @test = 0
+        attr_reader :test
+
+        def install
+          on_arm do
+            @test = 1
+          end
+          on_intel do
+            @test = 2
+          end
+        end
+      end.new
+    end
+
+    it "only calls code within on_intel" do
+      f.brew { f.install }
+      expect(f.test).to eq(2)
+    end
+  end
 end
diff --git a/Library/Homebrew/test/support/fixtures/cask/Casks/multiple-versions.rb b/Library/Homebrew/test/support/fixtures/cask/Casks/multiple-versions.rb
index 0107d0ec8a..ad05491a2d 100644
--- a/Library/Homebrew/test/support/fixtures/cask/Casks/multiple-versions.rb
+++ b/Library/Homebrew/test/support/fixtures/cask/Casks/multiple-versions.rb
@@ -1,12 +1,23 @@
 cask "multiple-versions" do
-  if MacOS.version == :test_os
-    version "1.2.0"
-  else
-    version "1.2.3"
-  end
+  arch = "arm"
+  version "1.2.3"
   sha256 "67cdb8a02803ef37fdbf7e0be205863172e41a561ca446cd84f0d7ab35a99d94"
 
-  url "file://#{TEST_FIXTURE_DIR}/cask/caffeine.zip"
+  on_intel do
+    arch = "intel"
+  end
+
+  on_big_sur do
+    version "1.2.0"
+    sha256 "8c62a2b791cf5f0da6066a0a4b6e85f62949cd60975da062df44adf887f4370b"
+  end
+
+  on_catalina :or_older do
+    version "1.0.0"
+    sha256 "1866dfa833b123bb8fe7fa7185ebf24d28d300d0643d75798bc23730af734216"
+  end
+
+  url "file://#{TEST_FIXTURE_DIR}/cask/caffeine/#{version}/#{arch}.zip"
   homepage "https://brew.sh/"
 
   app "Caffeine.app"

From f38db6e10046be7eb7ca3f334cd3f3b3e31f3345 Mon Sep 17 00:00:00 2001
From: Rylan Polster <rslpolster@gmail.com>
Date: Thu, 23 Jun 2022 17:49:08 -0400
Subject: [PATCH 04/10] Define `MacOS::Version::SYMBOLS` on macOS and linux

---
 Library/Homebrew/os.rb             | 21 +++++++++++++++++++++
 Library/Homebrew/os/linux.rb       |  6 ------
 Library/Homebrew/os/mac.rb         |  6 ------
 Library/Homebrew/os/mac/version.rb | 18 +++---------------
 4 files changed, 24 insertions(+), 27 deletions(-)

diff --git a/Library/Homebrew/os.rb b/Library/Homebrew/os.rb
index 52945a402a..b2d6c64cad 100644
--- a/Library/Homebrew/os.rb
+++ b/Library/Homebrew/os.rb
@@ -1,6 +1,8 @@
 # typed: true
 # frozen_string_literal: true
 
+require "version"
+
 # Helper functions for querying operating system information.
 #
 # @api private
@@ -48,6 +50,25 @@ module OS
   CI_GLIBC_VERSION = "2.23"
   CI_OS_VERSION = "Ubuntu 16.04"
 
+  module Mac
+    ::MacOS = OS::Mac
+
+    class Version < ::Version
+      # TODO: when removing symbols here, ensure that they are added to
+      # DEPRECATED_MACOS_VERSIONS in MacOSRequirement.
+      SYMBOLS = {
+        ventura:     "13",
+        monterey:    "12",
+        big_sur:     "11",
+        catalina:    "10.15",
+        mojave:      "10.14",
+        high_sierra: "10.13",
+        sierra:      "10.12",
+        el_capitan:  "10.11",
+      }.freeze
+    end
+  end
+
   if OS.mac?
     require "os/mac"
     # Don't tell people to report issues on unsupported configurations.
diff --git a/Library/Homebrew/os/linux.rb b/Library/Homebrew/os/linux.rb
index 6c029ef8be..57598261ef 100644
--- a/Library/Homebrew/os/linux.rb
+++ b/Library/Homebrew/os/linux.rb
@@ -31,12 +31,6 @@ module OS
   module Mac
     module_function
 
-    # rubocop:disable Naming/ConstantName
-    # rubocop:disable Style/MutableConstant
-    ::MacOS = OS::Mac
-    # rubocop:enable Naming/ConstantName
-    # rubocop:enable Style/MutableConstant
-
     raise "Loaded OS::Linux on generic OS!" if ENV["HOMEBREW_TEST_GENERIC_OS"]
 
     def version
diff --git a/Library/Homebrew/os/mac.rb b/Library/Homebrew/os/mac.rb
index bb75f0de9c..b23e62dd8b 100644
--- a/Library/Homebrew/os/mac.rb
+++ b/Library/Homebrew/os/mac.rb
@@ -13,12 +13,6 @@ module OS
 
     module_function
 
-    # rubocop:disable Naming/ConstantName
-    # rubocop:disable Style/MutableConstant
-    ::MacOS = OS::Mac
-    # rubocop:enable Naming/ConstantName
-    # rubocop:enable Style/MutableConstant
-
     raise "Loaded OS::Mac on generic OS!" if ENV["HOMEBREW_TEST_GENERIC_OS"]
 
     VERSION = ENV.fetch("HOMEBREW_MACOS_VERSION").chomp.freeze
diff --git a/Library/Homebrew/os/mac/version.rb b/Library/Homebrew/os/mac/version.rb
index 130d1c4f63..a7d183eaef 100644
--- a/Library/Homebrew/os/mac/version.rb
+++ b/Library/Homebrew/os/mac/version.rb
@@ -13,22 +13,10 @@ module OS
     class Version < ::Version
       extend T::Sig
 
-      # TODO: when removing symbols here, ensure that they are added to
-      # DEPRECATED_MACOS_VERSIONS in MacOSRequirement.
-      SYMBOLS = {
-        ventura:     "13",
-        monterey:    "12",
-        big_sur:     "11",
-        catalina:    "10.15",
-        mojave:      "10.14",
-        high_sierra: "10.13",
-        sierra:      "10.12",
-        el_capitan:  "10.11",
-      }.freeze
-
       # TODO: bump version when new macOS is released or announced
-      # and also update references in docs/Installation.md and
-      # https://github.com/Homebrew/install/blob/HEAD/install.sh
+      # and also update references in docs/Installation.md,
+      # https://github.com/Homebrew/install/blob/HEAD/install.sh and
+      # OS::Mac::Version (in HOMEBREW_LIBRARY/os.rb)
       NEWEST_UNSUPPORTED = "13"
       private_constant :NEWEST_UNSUPPORTED
 

From d96a8fd35e55269015ef8161d2021ed6c9f07496 Mon Sep 17 00:00:00 2001
From: Rylan Polster <rslpolster@gmail.com>
Date: Fri, 24 Jun 2022 17:20:03 -0400
Subject: [PATCH 05/10] Fix tests

---
 Library/Homebrew/test/cask/cmd/list_spec.rb | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/Library/Homebrew/test/cask/cmd/list_spec.rb b/Library/Homebrew/test/cask/cmd/list_spec.rb
index 8149e76210..6c0e3db2ff 100644
--- a/Library/Homebrew/test/cask/cmd/list_spec.rb
+++ b/Library/Homebrew/test/cask/cmd/list_spec.rb
@@ -246,10 +246,9 @@ describe Cask::Cmd::List, :cask do
         ]
       EOS
     }
+    let(:original_macos_version) { MacOS.full_version.to_s }
 
     before do
-      casks.map(&Cask::CaskLoader.method(:load)).each(&InstallHelper.method(:install_with_caskfile))
-
       # Use a more limited symbols list to shorten the variations hash
       symbols = {
         monterey: "12",
@@ -262,6 +261,12 @@ describe Cask::Cmd::List, :cask do
       # For consistency, always run on Monterey and ARM
       MacOS.full_version = "12"
       allow(Hardware::CPU).to receive(:type).and_return(:arm)
+
+      casks.map(&Cask::CaskLoader.method(:load)).each(&InstallHelper.method(:install_with_caskfile))
+    end
+
+    after do
+      MacOS.full_version = original_macos_version
     end
 
     it "of all installed Casks" do

From 5ec19adf58b18d0736be1b793164632fdf3f9b00 Mon Sep 17 00:00:00 2001
From: Rylan Polster <rslpolster@gmail.com>
Date: Tue, 28 Jun 2022 15:04:30 -0400
Subject: [PATCH 06/10] Rename `Override` module to `SimulateSystem`

---
 Library/Homebrew/cask/cask.rb                      |  6 +++---
 Library/Homebrew/cask/dsl.rb                       |  1 -
 Library/Homebrew/extend/on_system.rb               | 12 ++++++------
 .../Homebrew/{override.rb => simulate_system.rb}   |  7 ++-----
 Library/Homebrew/test/formula_spec.rb              | 14 +++++++-------
 5 files changed, 18 insertions(+), 22 deletions(-)
 rename Library/Homebrew/{override.rb => simulate_system.rb} (85%)

diff --git a/Library/Homebrew/cask/cask.rb b/Library/Homebrew/cask/cask.rb
index 40218642e5..90f5e756c0 100644
--- a/Library/Homebrew/cask/cask.rb
+++ b/Library/Homebrew/cask/cask.rb
@@ -255,8 +255,8 @@ module Cask
             # Big Sur is the first version of macOS that supports arm
             next if arch == :arm && MacOS::Version.from_symbol(os_name) < MacOS::Version.from_symbol(:big_sur)
 
-            Homebrew::Override.os = os_name
-            Homebrew::Override.arch = arch
+            Homebrew::SimulateSystem.os = os_name
+            Homebrew::SimulateSystem.arch = arch
 
             refresh
 
@@ -272,7 +272,7 @@ module Cask
         end
       end
 
-      Homebrew::Override.clear
+      Homebrew::SimulateSystem.clear
       refresh
 
       hash["variations"] = variations
diff --git a/Library/Homebrew/cask/dsl.rb b/Library/Homebrew/cask/dsl.rb
index 9a631484d1..1748d5fce0 100644
--- a/Library/Homebrew/cask/dsl.rb
+++ b/Library/Homebrew/cask/dsl.rb
@@ -4,7 +4,6 @@
 require "locale"
 require "lazy_object"
 require "livecheck"
-require "override"
 
 require "cask/artifact"
 
diff --git a/Library/Homebrew/extend/on_system.rb b/Library/Homebrew/extend/on_system.rb
index 711bb4b187..5490149e68 100644
--- a/Library/Homebrew/extend/on_system.rb
+++ b/Library/Homebrew/extend/on_system.rb
@@ -1,7 +1,7 @@
 # typed: false
 # frozen_string_literal: true
 
-require "override"
+require "simulate_system"
 
 module OnSystem
   extend T::Sig
@@ -13,9 +13,9 @@ module OnSystem
 
   sig { params(arch: Symbol).returns(T::Boolean) }
   def arch_condition_met?(arch)
-    raise ArgumentError, "Invalid arch condition: #{arch.inspect}" unless ARCH_OPTIONS.include?(arch)
+    raise ArgumentError, "Invalid arch condition: #{arch.inspect}" if ARCH_OPTIONS.exclude?(arch)
 
-    current_arch = Homebrew::Override.arch || Hardware::CPU.type
+    current_arch = Homebrew::SimulateSystem.arch || Hardware::CPU.type
     arch == current_arch
   end
 
@@ -27,12 +27,12 @@ module OnSystem
     end
 
     if BASE_OS_OPTIONS.include?(os_name)
-      if Homebrew::Override.none?
+      if Homebrew::SimulateSystem.none?
         return OS.linux? if os_name == :linux
         return OS.mac? if os_name == :macos
       end
 
-      return Homebrew::Override.send("#{os_name}?")
+      return Homebrew::SimulateSystem.send("#{os_name}?")
     end
 
     raise ArgumentError, "Invalid OS condition: #{os_name.inspect}" unless MacOS::Version::SYMBOLS.key?(os_name)
@@ -42,7 +42,7 @@ module OnSystem
     end
 
     base_os = MacOS::Version.from_symbol(os_name)
-    current_os = MacOS::Version.from_symbol(Homebrew::Override.os || MacOS.version.to_sym)
+    current_os = MacOS::Version.from_symbol(Homebrew::SimulateSystem.os || MacOS.version.to_sym)
 
     return current_os >= base_os if or_condition == :or_newer
     return current_os <= base_os if or_condition == :or_older
diff --git a/Library/Homebrew/override.rb b/Library/Homebrew/simulate_system.rb
similarity index 85%
rename from Library/Homebrew/override.rb
rename to Library/Homebrew/simulate_system.rb
index 7b6765ac5d..12d1e0e34d 100644
--- a/Library/Homebrew/override.rb
+++ b/Library/Homebrew/simulate_system.rb
@@ -2,16 +2,13 @@
 # frozen_string_literal: true
 
 module Homebrew
-  # Helper module for overriding machine-specific methods.
+  # Helper module for simulating different system condfigurations.
   #
   # @api private
-  class Override
+  class SimulateSystem
     class << self
       extend T::Sig
 
-      ARCH_OPTIONS = [:intel, :arm64].freeze
-      OS_OPTIONS = [:macos, :linux].freeze
-
       attr_reader :os, :arch
 
       sig { params(new_os: Symbol).void }
diff --git a/Library/Homebrew/test/formula_spec.rb b/Library/Homebrew/test/formula_spec.rb
index 58d70fcc5c..f9e3f93116 100644
--- a/Library/Homebrew/test/formula_spec.rb
+++ b/Library/Homebrew/test/formula_spec.rb
@@ -1583,11 +1583,11 @@ describe Formula do
 
   describe "on_{os_version} blocks", :needs_macos do
     before do
-      Homebrew::Override.os = :monterey
+      Homebrew::SimulateSystem.os = :monterey
     end
 
     after do
-      Homebrew::Override.clear
+      Homebrew::SimulateSystem.clear
     end
 
     let(:f) do
@@ -1610,31 +1610,31 @@ describe Formula do
     end
 
     it "only calls code within `on_monterey`" do
-      Homebrew::Override.os = :monterey
+      Homebrew::SimulateSystem.os = :monterey
       f.brew { f.install }
       expect(f.test).to eq(1)
     end
 
     it "only calls code within `on_monterey :or_newer`" do
-      Homebrew::Override.os = :ventura
+      Homebrew::SimulateSystem.os = :ventura
       f.brew { f.install }
       expect(f.test).to eq(1)
     end
 
     it "only calls code within `on_big_sur`" do
-      Homebrew::Override.os = :big_sur
+      Homebrew::SimulateSystem.os = :big_sur
       f.brew { f.install }
       expect(f.test).to eq(2)
     end
 
     it "only calls code within `on_catalina`" do
-      Homebrew::Override.os = :catalina
+      Homebrew::SimulateSystem.os = :catalina
       f.brew { f.install }
       expect(f.test).to eq(3)
     end
 
     it "only calls code within `on_catalina :or_older`" do
-      Homebrew::Override.os = :mojave
+      Homebrew::SimulateSystem.os = :mojave
       f.brew { f.install }
       expect(f.test).to eq(3)
     end

From ac067eedb2e64e024e77e126b652588a4a5dd58b Mon Sep 17 00:00:00 2001
From: Rylan Polster <rslpolster@gmail.com>
Date: Wed, 29 Jun 2022 11:29:46 -0400
Subject: [PATCH 07/10] Create `MacOSVersions` module

---
 Library/Homebrew/cask/cask.rb               |  4 ++--
 Library/Homebrew/cask/dsl/depends_on.rb     |  2 +-
 Library/Homebrew/extend/on_system.rb        |  6 +++---
 Library/Homebrew/global.rb                  |  1 +
 Library/Homebrew/macos_versions.rb          | 20 ++++++++++++++++++++
 Library/Homebrew/os.rb                      | 19 -------------------
 Library/Homebrew/os/linux.rb                |  2 ++
 Library/Homebrew/os/mac.rb                  |  2 ++
 Library/Homebrew/os/mac/version.rb          |  8 ++++----
 Library/Homebrew/simulate_system.rb         |  4 ++--
 Library/Homebrew/test/cask/cmd/list_spec.rb |  2 +-
 11 files changed, 38 insertions(+), 32 deletions(-)
 create mode 100644 Library/Homebrew/macos_versions.rb

diff --git a/Library/Homebrew/cask/cask.rb b/Library/Homebrew/cask/cask.rb
index 90f5e756c0..c30dfa7c22 100644
--- a/Library/Homebrew/cask/cask.rb
+++ b/Library/Homebrew/cask/cask.rb
@@ -94,7 +94,7 @@ module Cask
         version_os_hash = {}
         actual_version = MacOS.full_version.to_s
 
-        MacOS::Version::SYMBOLS.each do |os_name, os_version|
+        MacOSVersions::SYMBOLS.each do |os_name, os_version|
           MacOS.full_version = os_version
           cask = CaskLoader.load(token)
           version_os_hash[os_name] = cask.version if cask.version != version
@@ -251,7 +251,7 @@ module Cask
 
       if @dsl.on_system_blocks_exist?
         [:arm, :intel].each do |arch|
-          MacOS::Version::SYMBOLS.each_key do |os_name|
+          MacOSVersions::SYMBOLS.each_key do |os_name|
             # Big Sur is the first version of macOS that supports arm
             next if arch == :arm && MacOS::Version.from_symbol(os_name) < MacOS::Version.from_symbol(:big_sur)
 
diff --git a/Library/Homebrew/cask/dsl/depends_on.rb b/Library/Homebrew/cask/dsl/depends_on.rb
index d7ac942dfd..1d4e3a2448 100644
--- a/Library/Homebrew/cask/dsl/depends_on.rb
+++ b/Library/Homebrew/cask/dsl/depends_on.rb
@@ -55,7 +55,7 @@ module Cask
         begin
           @macos = if args.count > 1
             MacOSRequirement.new([args], comparator: "==")
-          elsif MacOS::Version::SYMBOLS.key?(args.first)
+          elsif MacOSVersions::SYMBOLS.key?(args.first)
             MacOSRequirement.new([args.first], comparator: "==")
           elsif /^\s*(?<comparator><|>|[=<>]=)\s*:(?<version>\S+)\s*$/ =~ args.first
             MacOSRequirement.new([version.to_sym], comparator: comparator)
diff --git a/Library/Homebrew/extend/on_system.rb b/Library/Homebrew/extend/on_system.rb
index 5490149e68..e008a6feca 100644
--- a/Library/Homebrew/extend/on_system.rb
+++ b/Library/Homebrew/extend/on_system.rb
@@ -23,7 +23,7 @@ module OnSystem
   def os_condition_met?(os_name, or_condition = nil)
     if Homebrew::EnvConfig.simulate_macos_on_linux?
       return false if os_name == :linux
-      return true if [:macos, *MacOS::Version::SYMBOLS.keys].include?(os_name)
+      return true if [:macos, *MacOSVersions::SYMBOLS.keys].include?(os_name)
     end
 
     if BASE_OS_OPTIONS.include?(os_name)
@@ -35,7 +35,7 @@ module OnSystem
       return Homebrew::SimulateSystem.send("#{os_name}?")
     end
 
-    raise ArgumentError, "Invalid OS condition: #{os_name.inspect}" unless MacOS::Version::SYMBOLS.key?(os_name)
+    raise ArgumentError, "Invalid OS condition: #{os_name.inspect}" unless MacOSVersions::SYMBOLS.key?(os_name)
 
     if or_condition.present? && [:or_newer, :or_older].exclude?(or_condition)
       raise ArgumentError, "Invalid OS `or_*` condition: #{or_condition.inspect}"
@@ -87,7 +87,7 @@ module OnSystem
       end
     end
 
-    MacOS::Version::SYMBOLS.each_key do |os_name|
+    MacOSVersions::SYMBOLS.each_key do |os_name|
       onto.define_method("on_#{os_name}") do |or_condition = nil, &block|
         @on_system_blocks_exist = true
 
diff --git a/Library/Homebrew/global.rb b/Library/Homebrew/global.rb
index 08a898c3aa..1a11464f69 100644
--- a/Library/Homebrew/global.rb
+++ b/Library/Homebrew/global.rb
@@ -72,6 +72,7 @@ HOMEBREW_BOTTLES_EXTNAME_REGEX = /\.([a-z0-9_]+)\.bottle\.(?:(\d+)\.)?tar\.gz$/.
 
 require "env_config"
 require "compat/early" unless Homebrew::EnvConfig.no_compat?
+require "macos_versions"
 require "os"
 require "messages"
 require "default_prefix"
diff --git a/Library/Homebrew/macos_versions.rb b/Library/Homebrew/macos_versions.rb
new file mode 100644
index 0000000000..16d4bd47e4
--- /dev/null
+++ b/Library/Homebrew/macos_versions.rb
@@ -0,0 +1,20 @@
+# typed: true
+# frozen_string_literal: true
+
+# Helper functions for querying operating system information.
+#
+# @api private
+module MacOSVersions
+  # TODO: when removing symbols here, ensure that they are added to
+  # DEPRECATED_MACOS_VERSIONS in MacOSRequirement.
+  SYMBOLS = {
+    ventura:     "13",
+    monterey:    "12",
+    big_sur:     "11",
+    catalina:    "10.15",
+    mojave:      "10.14",
+    high_sierra: "10.13",
+    sierra:      "10.12",
+    el_capitan:  "10.11",
+  }.freeze
+end
diff --git a/Library/Homebrew/os.rb b/Library/Homebrew/os.rb
index b2d6c64cad..3152c91389 100644
--- a/Library/Homebrew/os.rb
+++ b/Library/Homebrew/os.rb
@@ -50,25 +50,6 @@ module OS
   CI_GLIBC_VERSION = "2.23"
   CI_OS_VERSION = "Ubuntu 16.04"
 
-  module Mac
-    ::MacOS = OS::Mac
-
-    class Version < ::Version
-      # TODO: when removing symbols here, ensure that they are added to
-      # DEPRECATED_MACOS_VERSIONS in MacOSRequirement.
-      SYMBOLS = {
-        ventura:     "13",
-        monterey:    "12",
-        big_sur:     "11",
-        catalina:    "10.15",
-        mojave:      "10.14",
-        high_sierra: "10.13",
-        sierra:      "10.12",
-        el_capitan:  "10.11",
-      }.freeze
-    end
-  end
-
   if OS.mac?
     require "os/mac"
     # Don't tell people to report issues on unsupported configurations.
diff --git a/Library/Homebrew/os/linux.rb b/Library/Homebrew/os/linux.rb
index 57598261ef..c8fcc00e52 100644
--- a/Library/Homebrew/os/linux.rb
+++ b/Library/Homebrew/os/linux.rb
@@ -8,6 +8,8 @@ module OS
 
     module_function
 
+    ::MacOS = OS::Mac
+
     sig { returns(String) }
     def os_version
       if which("lsb_release")
diff --git a/Library/Homebrew/os/mac.rb b/Library/Homebrew/os/mac.rb
index b23e62dd8b..5f422450e9 100644
--- a/Library/Homebrew/os/mac.rb
+++ b/Library/Homebrew/os/mac.rb
@@ -13,6 +13,8 @@ module OS
 
     module_function
 
+    ::MacOS = OS::Mac
+
     raise "Loaded OS::Mac on generic OS!" if ENV["HOMEBREW_TEST_GENERIC_OS"]
 
     VERSION = ENV.fetch("HOMEBREW_MACOS_VERSION").chomp.freeze
diff --git a/Library/Homebrew/os/mac/version.rb b/Library/Homebrew/os/mac/version.rb
index a7d183eaef..a460141c50 100644
--- a/Library/Homebrew/os/mac/version.rb
+++ b/Library/Homebrew/os/mac/version.rb
@@ -30,7 +30,7 @@ module OS
 
       sig { params(version: Symbol).returns(T.attached_class) }
       def self.from_symbol(version)
-        str = SYMBOLS.fetch(version) { raise MacOSVersionError, version }
+        str = MacOSVersions::SYMBOLS.fetch(version) { raise MacOSVersionError, version }
         new(str)
       end
 
@@ -48,10 +48,10 @@ module OS
       sig { override.params(other: T.untyped).returns(T.nilable(Integer)) }
       def <=>(other)
         @comparison_cache.fetch(other) do
-          if SYMBOLS.key?(other) && to_sym == other
+          if MacOSVersions::SYMBOLS.key?(other) && to_sym == other
             0
           else
-            v = SYMBOLS.fetch(other) { other.to_s }
+            v = MacOSVersions::SYMBOLS.fetch(other) { other.to_s }
             @comparison_cache[other] = super(::Version.new(v))
           end
         end
@@ -69,7 +69,7 @@ module OS
 
       sig { returns(Symbol) }
       def to_sym
-        @to_sym ||= SYMBOLS.invert.fetch(strip_patch.to_s, :dunno)
+        @to_sym ||= MacOSVersions::SYMBOLS.invert.fetch(strip_patch.to_s, :dunno)
       end
 
       sig { returns(String) }
diff --git a/Library/Homebrew/simulate_system.rb b/Library/Homebrew/simulate_system.rb
index 12d1e0e34d..d52a2af752 100644
--- a/Library/Homebrew/simulate_system.rb
+++ b/Library/Homebrew/simulate_system.rb
@@ -13,7 +13,7 @@ module Homebrew
 
       sig { params(new_os: Symbol).void }
       def os=(new_os)
-        os_options = [:macos, :linux, *MacOS::Version::SYMBOLS.keys]
+        os_options = [:macos, :linux, *MacOSVersions::SYMBOLS.keys]
         raise "Unknown OS: #{new_os}" unless os_options.include?(new_os)
 
         @os = new_os
@@ -38,7 +38,7 @@ module Homebrew
 
       sig { returns(T::Boolean) }
       def macos?
-        [:macos, *MacOS::Version::SYMBOLS.keys].include?(@os)
+        [:macos, *MacOSVersions::SYMBOLS.keys].include?(@os)
       end
 
       sig { returns(T::Boolean) }
diff --git a/Library/Homebrew/test/cask/cmd/list_spec.rb b/Library/Homebrew/test/cask/cmd/list_spec.rb
index 6c0e3db2ff..77b6e7af89 100644
--- a/Library/Homebrew/test/cask/cmd/list_spec.rb
+++ b/Library/Homebrew/test/cask/cmd/list_spec.rb
@@ -256,7 +256,7 @@ describe Cask::Cmd::List, :cask do
         catalina: "10.15",
         mojave:   "10.14",
       }
-      stub_const("MacOS::Version::SYMBOLS", symbols)
+      stub_const("MacOSVersions::SYMBOLS", symbols)
 
       # For consistency, always run on Monterey and ARM
       MacOS.full_version = "12"

From a9e62b9e38826807d8de11b210a560550f285f9f Mon Sep 17 00:00:00 2001
From: Rylan Polster <rslpolster@gmail.com>
Date: Wed, 29 Jun 2022 11:38:55 -0400
Subject: [PATCH 08/10] `include OnSystem` to define DSL methods

---
 Library/Homebrew/cask/dsl.rb         |  3 +--
 Library/Homebrew/extend/on_system.rb | 26 ++++++++++++--------------
 Library/Homebrew/formula.rb          |  6 ++----
 Library/Homebrew/resource.rb         |  3 +--
 Library/Homebrew/software_spec.rb    |  5 ++---
 5 files changed, 18 insertions(+), 25 deletions(-)

diff --git a/Library/Homebrew/cask/dsl.rb b/Library/Homebrew/cask/dsl.rb
index 1748d5fce0..6367141d8c 100644
--- a/Library/Homebrew/cask/dsl.rb
+++ b/Library/Homebrew/cask/dsl.rb
@@ -92,6 +92,7 @@ module Cask
     ]).freeze
 
     extend Predicable
+    include OnSystem
 
     attr_reader :cask, :token
 
@@ -319,8 +320,6 @@ module Cask
       @livecheckable == true
     end
 
-    OnSystem.setup_methods! onto: self, include_linux: false
-
     ORDINARY_ARTIFACT_CLASSES.each do |klass|
       define_method(klass.dsl_key) do |*args|
         if [*artifacts.map(&:class), klass].include?(Artifact::StageOnly) &&
diff --git a/Library/Homebrew/extend/on_system.rb b/Library/Homebrew/extend/on_system.rb
index e008a6feca..01e489b0f4 100644
--- a/Library/Homebrew/extend/on_system.rb
+++ b/Library/Homebrew/extend/on_system.rb
@@ -55,10 +55,10 @@ module OnSystem
     method_name.to_s.sub(/^on_/, "").to_sym
   end
 
-  sig { params(onto: Class, include_linux: T::Boolean).void }
-  def setup_methods!(onto:, include_linux: true)
+  sig { params(base: Class).void }
+  def self.included(base)
     ARCH_OPTIONS.each do |arch|
-      onto.define_method("on_#{arch}") do |&block|
+      base.define_method("on_#{arch}") do |&block|
         @on_system_blocks_exist = true
 
         return unless OnSystem.arch_condition_met? OnSystem.condition_from_method_name(__method__)
@@ -71,24 +71,22 @@ module OnSystem
       end
     end
 
-    if include_linux
-      BASE_OS_OPTIONS.each do |base_os|
-        onto.define_method("on_#{base_os}") do |&block|
-          @on_system_blocks_exist = true
+    BASE_OS_OPTIONS.each do |base_os|
+      base.define_method("on_#{base_os}") do |&block|
+        @on_system_blocks_exist = true
 
-          return unless OnSystem.os_condition_met? OnSystem.condition_from_method_name(__method__)
+        return unless OnSystem.os_condition_met? OnSystem.condition_from_method_name(__method__)
 
-          @called_in_on_system_block = true
-          result = block.call
-          @called_in_on_system_block = false
+        @called_in_on_system_block = true
+        result = block.call
+        @called_in_on_system_block = false
 
-          result
-        end
+        result
       end
     end
 
     MacOSVersions::SYMBOLS.each_key do |os_name|
-      onto.define_method("on_#{os_name}") do |or_condition = nil, &block|
+      base.define_method("on_#{os_name}") do |or_condition = nil, &block|
         @on_system_blocks_exist = true
 
         os_condition = OnSystem.condition_from_method_name __method__
diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index 250583b465..09ede72647 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -64,12 +64,11 @@ class Formula
   include Utils::Shebang
   include Utils::Shell
   include Context
+  include OnSystem
   extend Forwardable
   extend Cachable
   extend Predicable
 
-  OnSystem.setup_methods! onto: self
-
   # @!method inreplace(paths, before = nil, after = nil)
   # @see Utils::Inreplace.inreplace
 
@@ -2471,6 +2470,7 @@ class Formula
   # The methods below define the formula DSL.
   class << self
     include BuildEnvironment::DSL
+    include OnSystem
 
     def method_added(method)
       super
@@ -2483,8 +2483,6 @@ class Formula
       end
     end
 
-    OnSystem.setup_methods! onto: self
-
     # The reason for why this software is not linked (by default) to
     # {::HOMEBREW_PREFIX}.
     # @private
diff --git a/Library/Homebrew/resource.rb b/Library/Homebrew/resource.rb
index 9cbd64bc7f..9d407c5aab 100644
--- a/Library/Homebrew/resource.rb
+++ b/Library/Homebrew/resource.rb
@@ -17,8 +17,7 @@ class Resource
 
   include Context
   include FileUtils
-
-  OnSystem.setup_methods! onto: self
+  include OnSystem
 
   attr_reader :mirrors, :specs, :using, :source_modified_time, :patches, :owner
   attr_writer :version
diff --git a/Library/Homebrew/software_spec.rb b/Library/Homebrew/software_spec.rb
index 61a0b8d463..35734f1aa5 100644
--- a/Library/Homebrew/software_spec.rb
+++ b/Library/Homebrew/software_spec.rb
@@ -18,14 +18,13 @@ class SoftwareSpec
   extend T::Sig
 
   extend Forwardable
+  include OnSystem
 
   PREDEFINED_OPTIONS = {
     universal: Option.new("universal", "Build a universal binary"),
     cxx11:     Option.new("c++11",     "Build using C++11 mode"),
   }.freeze
 
-  OnSystem.setup_methods! onto: self
-
   attr_reader :name, :full_name, :owner, :build, :resources, :patches, :options, :deprecated_flags,
               :deprecated_options, :dependency_collector, :bottle_specification, :compiler_failures,
               :uses_from_macos_elements
@@ -584,7 +583,7 @@ class BottleSpecification
 end
 
 class PourBottleCheck
-  OnSystem.setup_methods! onto: self
+  include OnSystem
 
   def initialize(formula)
     @formula = formula

From 1294de9e4878d69019c73aee57328ae1b9ca59ef Mon Sep 17 00:00:00 2001
From: Rylan Polster <rslpolster@gmail.com>
Date: Wed, 29 Jun 2022 11:45:02 -0400
Subject: [PATCH 09/10] Fix `Formula::on_macos` type annotation

---
 Library/Homebrew/formula.rbi | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Library/Homebrew/formula.rbi b/Library/Homebrew/formula.rbi
index a47b034dee..f77f4c0c50 100644
--- a/Library/Homebrew/formula.rbi
+++ b/Library/Homebrew/formula.rbi
@@ -49,6 +49,6 @@ class Formula
   def env; end
   def conflicts; end
 
-  # This method is generated by `OnSystem::setup_methods!`
+  # This method is included by `OnSystem`
   def self.on_macos(&block); end
 end

From b271ae151b7e06d7179687aafab2fa5dab9a3984 Mon Sep 17 00:00:00 2001
From: Rylan Polster <rslpolster@gmail.com>
Date: Wed, 29 Jun 2022 11:47:57 -0400
Subject: [PATCH 10/10] Cleanup

---
 Library/Homebrew/os.rb             | 2 --
 Library/Homebrew/os/linux.rb       | 4 ++--
 Library/Homebrew/os/mac/version.rb | 2 +-
 3 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/Library/Homebrew/os.rb b/Library/Homebrew/os.rb
index 3152c91389..52945a402a 100644
--- a/Library/Homebrew/os.rb
+++ b/Library/Homebrew/os.rb
@@ -1,8 +1,6 @@
 # typed: true
 # frozen_string_literal: true
 
-require "version"
-
 # Helper functions for querying operating system information.
 #
 # @api private
diff --git a/Library/Homebrew/os/linux.rb b/Library/Homebrew/os/linux.rb
index c8fcc00e52..277e3de3a9 100644
--- a/Library/Homebrew/os/linux.rb
+++ b/Library/Homebrew/os/linux.rb
@@ -8,8 +8,6 @@ module OS
 
     module_function
 
-    ::MacOS = OS::Mac
-
     sig { returns(String) }
     def os_version
       if which("lsb_release")
@@ -33,6 +31,8 @@ module OS
   module Mac
     module_function
 
+    ::MacOS = OS::Mac
+
     raise "Loaded OS::Linux on generic OS!" if ENV["HOMEBREW_TEST_GENERIC_OS"]
 
     def version
diff --git a/Library/Homebrew/os/mac/version.rb b/Library/Homebrew/os/mac/version.rb
index a460141c50..5f86f697a2 100644
--- a/Library/Homebrew/os/mac/version.rb
+++ b/Library/Homebrew/os/mac/version.rb
@@ -16,7 +16,7 @@ module OS
       # TODO: bump version when new macOS is released or announced
       # and also update references in docs/Installation.md,
       # https://github.com/Homebrew/install/blob/HEAD/install.sh and
-      # OS::Mac::Version (in HOMEBREW_LIBRARY/os.rb)
+      # MacOSVersions::SYMBOLS
       NEWEST_UNSUPPORTED = "13"
       private_constant :NEWEST_UNSUPPORTED