Use Ruby 2-style keywords via the ruby2_keywords method flag

lib/memoist.rb

@@ -203,7 +203,7 @@ def #{method_name}(reload = false)
           # end
 
           module_eval <<-EOS, __FILE__, __LINE__ + 1
-            def #{method_name}(*args)
+            ruby2_keywords def #{method_name}(*args)
               reload = Memoist.extract_reload!(method(#{unmemoized_method.inspect}), args)
 
               skip_cache = reload || !(instance_variable_defined?(#{memoized_ivar.inspect}) && #{memoized_ivar} && #{memoized_ivar}.has_key?(args))

memoist.gemspec

@@ -37,10 +37,15 @@ Gem::Specification.new do |spec|
 
   spec.add_development_dependency 'benchmark-ips'
   spec.add_development_dependency 'bundler'
+  spec.add_development_dependency 'minitest', '~> 5.10'
+
   if RUBY_VERSION < '1.9.3'
     spec.add_development_dependency 'rake', '~> 10.4'
   else
     spec.add_development_dependency 'rake'
   end
-  spec.add_development_dependency 'minitest', '~> 5.10'
+
+  if RUBY_VERSION < '3.0.0'
+    spec.add_dependency 'ruby2_keywords'
+  end
 end

test/memoist_test.rb

@@ -74,9 +74,40 @@ def update_attributes(_options = {})
     end
     memoize :update_attributes
 
-    def update_attributes_calls
-      @counter.count(:update_attributes)
+    def rest(*args)
+      counter.call(:rest)
+
+      args.each_with_index.each_with_object({}) do |(arg, i), memo|
+        memo[i + 1] = arg
+      end
+    end
+    memoize :rest
+
+    def rest_and_kwargs(*args, **options)
+      counter.call(:rest_and_kwargs)
+
+      i = 0
+
+      rest = args.each_with_object({}) do |arg, memo|
+        memo[i += 1] = arg
+      end
+
+      kwargs = options.each_with_object({}) do |(key, value), memo|
+        memo[i += 1] = [key, value]
+      end
+
+      { rest: rest, kwargs: kwargs }
+    end
+    memoize :rest_and_kwargs
+
+    def kwargs(**options)
+      counter.call(:kwargs)
+
+      options.each_with_index.each_with_object({}) do |((key, value), i), memo|
+        memo[i += 1] = [key, value]
+      end
     end
+    memoize :kwargs
 
     protected
 
@@ -338,7 +369,7 @@ def test_all_memoized_structs
     # Student < Person   memoize :name, :identifier => :student
     # Teacher < Person   memoize :seniority
 
-    expected = %w[age age? is_developer? memoize_protected_test name name? sleep update update_attributes]
+    expected = %w[age age? is_developer? memoize_protected_test name name? sleep update update_attributes rest rest_and_kwargs kwargs].sort
     structs = Person.all_memoized_structs
     assert_equal expected, structs.collect(&:memoized_method).collect(&:to_s).sort
     assert_equal '@_memoized_name', structs.detect { |s| s.memoized_method == :name }.ivar
@@ -537,4 +568,49 @@ def test_private_method_memoization
     assert_equal 'Yes', person.send(:is_developer?)
     assert_equal 1, person.calls(:is_developer?)
   end
+
+  def test_rest
+    person = Person.new
+
+    3.times do
+      assert_equal({ 1 => :one, 2 => :two, 3 => :three }, person.rest(:one, :two, :three))
+    end
+
+    assert_equal 1, person.calls(:rest)
+  end
+
+  def test_rest_and_kwargs
+    person = Person.new
+
+    3.times do
+      assert_equal({
+        rest: {
+          1 => :one,
+          2 => :two,
+          3 => :three
+        },
+        kwargs: {
+          4 => [:four, :five],
+          5 => [:six, :seven]
+        }
+      },
+      person.rest_and_kwargs(:one, :two, :three, four: :five, six: :seven))
+    end
+
+    assert_equal 1, person.calls(:rest_and_kwargs)
+  end
+
+  def test_kwargs
+    person = Person.new
+
+    3.times do
+      assert_equal({
+        1 => [:four, :five],
+        2 => [:six, :seven]
+      },
+      person.kwargs(four: :five, six: :seven))
+    end
+
+    assert_equal 1, person.calls(:kwargs)
+  end
 end