Tap.each: return an enumerable when no block given

Library/Homebrew/tap.rb

@@ -486,6 +486,8 @@ class Tap
   def self.each
     return unless TAP_DIRECTORY.directory?
 
+    return to_enum unless block_given?
+
     TAP_DIRECTORY.subdirs.each do |user|
       user.subdirs.each do |repo|
         yield fetch(user.basename.to_s, repo.basename.to_s)

Library/Homebrew/test/tap_spec.rb

@@ -297,6 +297,12 @@ describe Tap do
     subject.config["foo"] = nil
     expect(subject.config["foo"]).to be nil
   end
+
+  describe "#each" do
+    it "returns an enumerator if no block is passed" do
+      expect(described_class.each).to be_an_instance_of(Enumerator)
+    end
+  end
 end
 
 describe CoreTap do