Merge pull request rails#42020 from chaymaeBZ/merge-params-when-it-is-a-hash

 Only merge params option if params is a Hash in url_for helper

Author: tenderlove

actionpack/lib/action_dispatch/routing/route_set.rb

@@ -822,8 +822,10 @@ def url_for(options, route_name = nil, url_strategy = UNKNOWN, method_name = nil
         path = route_with_params.path(method_name)
         params = route_with_params.params
 
-        if options.key? :params
+        if options[:params].is_a?(Hash)
           params.merge! options[:params]
+        elsif options.key? :params
+          params[:params] = options[:params]
         end
 
         options[:path]        = path

actionpack/test/controller/url_for_test.rb

@@ -362,6 +362,13 @@ def test_params_option
         assert_equal({ id: "1" }.to_query, params[1])
       end
 
+      def test_non_hash_params_option
+        url = W.new.url_for(only_path: true, controller: "c", action: "a", params: "p")
+        params = extract_params(url)
+        assert_equal("/c/a?params=p", url)
+        assert_equal({ params: "p" }.to_query, params[0])
+      end
+
       def test_hash_parameter
         url = W.new.url_for(only_path: true, controller: "c", action: "a", query: { name: "Bob", category: "prof" })
         params = extract_params(url)