Support `Object#with_options` without a block

When the block argument is omitted, the decorated Object instance is returned:

```ruby
 # app/helpers/my_styled_helpers.rb
 module MyStyledHelpers
   def styled
     with_options style: "color: red;"
   end
 end

 # styled.link_to "I'm red", "/"
 # #=> <a href="/" style="color: red;">I'm red</a>

 # styled.button_tag "I'm red too!"
 # #=> <button style="color: red;">I'm red too!</button>
```

activesupport/CHANGELOG.md

@@ -1,3 +1,8 @@
+*   Invoking `Object#with_options` without a `&block` argument returns the
+    `ActiveSupport::OptionMerger` instance.
+
+    *Sean Doyle*
+
 *   `Rails.application.executor` hooks are now called around every tests.
 
     This helps to better simulate request or job local state being reset around tests and prevent state

activesupport/lib/active_support/core_ext/object/with_options.rb

@@ -75,8 +75,27 @@ class Object
   #     end
   #   end
   #
+  # When the block argument is omitted, the decorated Object instance is returned:
+  #
+  #   module MyStyledHelpers
+  #     def styled
+  #       with_options style: "color: red;"
+  #     end
+  #   end
+  #
+  #   # styled.link_to "I'm red", "/"
+  #   # #=> <a href="/" style="color: red;">I'm red</a>
+  #
+  #   # styled.button_tag "I'm red too!"
+  #   # #=> <button style="color: red;">I'm red too!</button>
+  #
   def with_options(options, &block)
     option_merger = ActiveSupport::OptionMerger.new(self, options)
-    block.arity.zero? ? option_merger.instance_eval(&block) : block.call(option_merger)
+
+    if block.nil?
+      option_merger
+    else
+      block.arity.zero? ? option_merger.instance_eval(&block) : block.call(option_merger)
+    end
   end
 end

activesupport/lib/active_support/option_merger.rb

@@ -30,5 +30,9 @@ module ActiveSupport
           @context.__send__(method, *arguments, &block)
         end
       end
+
+      def respond_to_missing?(*arguments)
+        @context.respond_to?(*arguments)
+      end
   end
 end

activesupport/test/option_merger_test.rb

@@ -105,6 +105,14 @@ class OptionMergerTest < ActiveSupport::TestCase
     assert_equal expected, @options
   end
 
+  def test_with_options_no_block
+    local_options = { "cool" => true }
+    scope = with_options(@options)
+
+    assert_equal local_options, method_with_options(local_options)
+    assert_equal @options.merge(local_options), scope.method_with_options(local_options)
+  end
+
   private
     def method_with_options(options = {})
       options