Merge pull request #12912 from Homebrew/formula_remove_include_on_os

formula: remove `OnOS`.

Library/Homebrew/compat/formula.rb

@@ -2,6 +2,18 @@
 # frozen_string_literal: true
 
 class Formula
+  extend OnOS
+
+  def on_macos(&block)
+    odeprecated "`on_macos do` inside `Formula` methods", "`if OS.mac?`"
+    super
+  end
+
+  def on_linux(&block)
+    odeprecated "`on_linux do` inside `Formula` methods", "`if OS.linux?`"
+    super
+  end
+
   extend Enumerable
 
   def self.each(&_block)

Library/Homebrew/formula.rb

@@ -64,7 +64,6 @@ class Formula
   include Utils::Shebang
   include Utils::Shell
   include Context
-  include OnOS # TODO: 3.4.0: odeprecate OnOS usage in instance methods.
   extend Forwardable
   extend Cachable
   extend Predicable

Library/Homebrew/test/formula_spec.rb

@@ -1534,50 +1534,4 @@ describe Formula do
       expect(f.any_installed_version).to eq(PkgVersion.parse("1.0_1"))
     end
   end
-
-  describe "#on_macos", :needs_macos do
-    let(:f) do
-      Class.new(Testball) do
-        @test = 0
-        attr_reader :test
-
-        def install
-          on_macos do
-            @test = 1
-          end
-          on_linux do
-            @test = 2
-          end
-        end
-      end.new
-    end
-
-    it "only calls code within on_macos" do
-      f.brew { f.install }
-      expect(f.test).to eq(1)
-    end
-  end
-
-  describe "#on_linux", :needs_linux do
-    let(:f) do
-      Class.new(Testball) do
-        @test = 0
-        attr_reader :test
-
-        def install
-          on_macos do
-            @test = 1
-          end
-          on_linux do
-            @test = 2
-          end
-        end
-      end.new
-    end
-
-    it "only calls code within on_linux" do
-      f.brew { f.install }
-      expect(f.test).to eq(2)
-    end
-  end
 end