Fix missing formats in route-set URLs

Before this change, handle_positional_args would end up mutating @segment_keys
if inner_options included path components.  Subsequent calls would then
be missing the implicit path components.

eg:
user_path(1, :json)         # => "/users/1.json" (correct)
user_path(1, format: :json) # => "/users/1.json" (correct, but @segment_keys was mutated)
user_path(1, :json)         # => "/users/1" (oh no!)

1 files changed, 9 insertions, 0 deletions

diff --git a/actionpack/test/dispatch/routing/route_set_test.rb b/actionpack/test/dispatch/routing/route_set_test.rb
index ace35dda53..d6ecbda092 100644
--- a/actionpack/test/dispatch/routing/route_set_test.rb
+++ b/actionpack/test/dispatch/routing/route_set_test.rb
@@ -138,6 +138,15 @@ module ActionDispatch
         assert_equal "/a/users/1", url_helpers.user_path(1, foo: "a")
       end
 
+      test "implicit path components consistently return the same result" do
+        draw do
+          resources :users, to: SimpleApp.new("foo#index")
+        end
+        assert_equal "/users/1.json", url_helpers.user_path(1, :json)
+        assert_equal "/users/1.json", url_helpers.user_path(1, format: :json)
+        assert_equal "/users/1.json", url_helpers.user_path(1, :json)
+      end
+
       private
         def draw(&block)
           @set.draw(&block)