Undefine #to_ary in ActionController::Live::Buffer

ActionDispatch::Response delegates #to_ary to the internal ActionDispatch::Response::Buffer,
defining #to_ary is an indicator that the response body can be buffered and/or cached by
Rack middlewares, this is not the case for Live responses so we undefine it for this Buffer subclass.

Puma raises an exception trying to call #to_ary in Live::Buffer
expecting it to return an array if defined:

https://github.com/puma/puma/blob/188f5da1920ff99a8689b3e9b46f2f26b7c62d66/lib/puma/request.rb#L183-L186

actionpack/lib/action_controller/metal/live.rb

@@ -167,6 +167,11 @@ def initialize(response)
         @ignore_disconnect = false
       end
 
+      # ActionDispatch::Response delegates #to_ary to the internal ActionDispatch::Response::Buffer,
+      # defining #to_ary is an indicator that the response body can be buffered and/or cached by
+      # Rack middlewares, this is not the case for Live responses so we undefine it for this Buffer subclass.
+      undef_method :to_ary
+
       def write(string)
         unless @response.committed?
           @response.headers["Cache-Control"] ||= "no-cache"

actionpack/test/controller/live_stream_test.rb

@@ -319,6 +319,11 @@ def ignore_client_disconnect
         logger.info "Work complete"
         latch.count_down
       end
+
+      def buffer_do_not_respond_to_to_ary
+        response.stream.write "response.stream.respond_to? = #{response.stream.respond_to?(:to_ary)}"
+        response.stream.close
+      end
     end
 
     tests TestController
@@ -596,6 +601,11 @@ def test_stale_with_etag
       get :with_stale
       assert_equal 304, response.status.to_i
     end
+
+    def test_response_buffer_do_not_respond_to_to_ary
+      get :buffer_do_not_respond_to_to_ary
+      assert_equal "response.stream.respond_to? = false", response.body
+    end
   end
 
   class BufferTest < ActionController::TestCase