formula: add versioned formulae method.

Library/Homebrew/dev-cmd/audit.rb

@@ -251,11 +251,9 @@ module Homebrew
           problem "#{formula} is versioned but no #{unversioned_name} formula exists"
         end
       elsif ARGV.build_stable? && formula.stable? &&
-            !(versioned_formulae = Dir[formula.path.to_s.gsub(/\.rb$/, "@*.rb")]).empty?
+            !(versioned_formulae = formula.versioned_formulae).empty?
         versioned_aliases = formula.aliases.grep(/.@\d/)
-        _, last_alias_version =
-          File.basename(versioned_formulae.sort.reverse.first)
-              .gsub(/\.rb$/, "").split("@")
+        _, last_alias_version = versioned_formulae.map(&:name).last.split("@")
         major, minor, = formula.version.to_s.split(".")
         alias_name_major = "#{formula.name}@#{major}"
         alias_name_major_minor = "#{alias_name_major}.#{minor}"

Library/Homebrew/formula.rb

@@ -370,6 +370,15 @@ class Formula
     name.include?("@")
   end
 
+  # Returns any `@`-versioned formulae for an non-`@`-versioned formula.
+  def versioned_formulae
+    return [] if versioned_formula?
+
+    Pathname.glob(path.to_s.gsub(/\.rb$/, "@*.rb")).map do |path|
+      Formula[path.basename(".rb").to_s]
+    end.sort
+  end
+
   # A named Resource for the currently active {SoftwareSpec}.
   # Additional downloads can be defined as {#resource}s.
   # {Resource#stage} will create a temporary directory and yield to a block.

Library/Homebrew/test/formula_spec.rb

@@ -107,6 +107,56 @@ describe Formula do
     end
   end
 
+  describe "#versioned_formula?" do
+    let(:f) do
+      formula "foo" do
+        url "foo-1.0"
+      end
+    end
+
+    let(:f2) do
+      formula "foo@2.0" do
+        url "foo-2.0"
+      end
+    end
+
+    it "returns true for @-versioned formulae" do
+      expect(f2.versioned_formula?).to be true
+    end
+
+    it "returns false for non-@-versioned formulae" do
+      expect(f.versioned_formula?).to be false
+    end
+  end
+
+  describe "#versioned_formulae" do
+    let(:f) do
+      formula "foo" do
+        url "foo-1.0"
+      end
+    end
+
+    let(:f2) do
+      formula "foo@2.0" do
+        url "foo-2.0"
+      end
+    end
+
+    it "returns true by default" do
+      FileUtils.touch f.path
+      FileUtils.touch f2.path
+      allow(Formulary).to receive(:load_formula_from_path).with(f2.name, f2.path).and_return(f2)
+      allow(Formulary).to receive(:factory).with(f2.name).and_return(f2)
+      expect(f.versioned_formulae).to eq [f2]
+    end
+
+    it "returns empty array for non-@-versioned formulae" do
+      FileUtils.touch f.path
+      FileUtils.touch f2.path
+      expect(f2.versioned_formulae).to be_empty
+    end
+  end
+
   example "installed alias with core" do
     f = formula do
       url "foo-1.0"
@@ -708,7 +758,7 @@ describe Formula do
       expect(f3.runtime_dependencies.map(&:name)).to eq(["foo/bar/f1", "baz/qux/f2"])
     end
 
-    it "includes non-declared direct dependencies", :focus do
+    it "includes non-declared direct dependencies" do
       formula = Class.new(Testball).new
       dependency = formula("dependency") { url "f-1.0" }