ActionDispatch::Routing::RouteSet#recognize_path does not reset parameters between trying different constraints out. It only adds parameters. Normal matching doesn't exhibit the same behavior and there's a test to make sure of it

Steps to reproduce

Add the following code to actionpack/test/controller/routing_test.rb

  def test_recognize_path_does_not_leak_params
    rs.draw do
      get ':foo/bar' => 'bar#foo', constraints: lambda { |*| false }
      get 'foo/:bar' => 'foo#bar'
    end

    assert_equal({ :controller => "foo", :action => 'bar', :bar => 'bar' }, rs.recognize_path("/foo/bar"))
  end

As you can see the :foo parameter was leaked from the first route with non-matching constraint.

Expected behavior

No failure

Actual behavior

  1) Failure:
LegacyRouteSetTests#test_recognize_path_does_not_leak_params [test/controller/routing_test.rb:673]:
--- expected
+++ actual
@@ -1 +1 @@
-{:controller=>"foo", :action=>"bar", :bar=>"bar"}
+{:controller=>"foo", :action=>"bar", :foo=>"foo", :bar=>"bar"}

System configuration

Rails version: 5.0.2, master

Ruby version: 2.3.3