Extends SoftwareSpec with #uses_from_macos

Library/Homebrew/extend/os/mac/software_spec.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+class SoftwareSpec
+  def uses_from_macos(deps, **args)
+    depends_on(deps) if add_mac_dependency?(args)
+  end
+
+  private
+
+  def add_mac_dependency?(args)
+    args.each { |key, version| args[key] = OS::Mac::Version.from_symbol(version) }
+
+    return false if args[:after] && OS::Mac.version < args[:after]
+
+    return false if args[:before] && OS::Mac.version >= args[:before]
+
+    true
+  end
+end

Library/Homebrew/extend/os/software_spec.rb

@@ -1,3 +1,7 @@
 # frozen_string_literal: true
 
-require "extend/os/linux/software_spec" if OS.linux?
+if OS.linux?
+  require "extend/os/linux/software_spec"
+elsif OS.mac?
+  require "extend/os/mac/software_spec"
+end

Library/Homebrew/formula.rb

@@ -2360,8 +2360,8 @@ class Formula
       specs.each { |spec| spec.depends_on(dep) }
     end
 
-    def uses_from_macos(dep, **_args)
-      depends_on(dep)
+    def uses_from_macos(dep, **args)
+      specs.each { |spec| spec.uses_from_macos(dep, args) }
     end
 
     # @!attribute [w] option

Library/Homebrew/software_spec.rb

@@ -170,6 +170,10 @@ class SoftwareSpec
     add_dep_option(dep) if dep
   end
 
+  def uses_from_macos(spec, **_args)
+    depends_on(spec)
+  end
+
   def deps
     dependency_collector.deps
   end

Library/Homebrew/test/os/mac/software_spec_spec.rb

@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+require "software_spec"
+
+describe SoftwareSpec do
+  describe "#uses_from_macos" do
+    before do
+      sierra_os_version = OS::Mac::Version.from_symbol(:sierra)
+
+      allow(OS).to receive(:mac?).and_return(true)
+      allow(OS::Mac).to receive(:version).and_return(OS::Mac::Version.new(sierra_os_version))
+    end
+
+    it "doesn't adds a dependency if it doesn't meet OS version requirements" do
+      subject.uses_from_macos("foo", after: :high_sierra)
+      subject.uses_from_macos("bar", before: :el_capitan)
+
+      expect(subject.deps).to be_empty
+    end
+
+    it "allows specifying dependencies after certain version" do
+      subject.uses_from_macos("foo", after: :el_capitan)
+
+      expect(subject.deps.first.name).to eq("foo")
+    end
+
+    it "works with tags" do
+      subject.uses_from_macos("foo" => :head, after: :el_capitan)
+
+      dep = subject.deps.first
+
+      expect(dep.name).to eq("foo")
+      expect(dep.tags).to include(:head)
+    end
+
+    it "allows specifying dependencies before certain version" do
+      subject.uses_from_macos("foo", before: :high_sierra)
+
+      expect(subject.deps.first.name).to eq("foo")
+    end
+
+    it "raises an error if passing invalid OS versions" do
+      expect {
+        subject.uses_from_macos("foo", after: "bar", before: :mojave)
+      }.to raise_error(ArgumentError, 'unknown version "bar"')
+    end
+  end
+end