Revert "Don't handle params option in a special way in url_for helper"

This reverts commit e385e4678f.

While this option was undocumented it exists to make possible to pass
parameters to the route helpers that are reserved like `:domain`.

While `url_for(domain: 'foo.com')` would generate a URL in the `foo.com`
domain `url_for(params: { domain: 'foo.com' })` would generate a URL
with `?domain=foo.com`.

actionpack/CHANGELOG.md

@@ -85,10 +85,6 @@
 
     *Yoshiyuki Kinjo*
 
-*   Remove undocumented `params` option from `url_for` helper.
-
-    *Ilkka Oksanen*
-
 *   Encode Content-Disposition filenames on `send_data` and `send_file`.
     Previously, `send_data 'data', filename: "\u{3042}.txt"` sends
     `"filename=\"\u{3042}.txt\""` as Content-Disposition and it can be

actionpack/lib/action_dispatch/routing/route_set.rb

@@ -820,6 +820,10 @@ module ActionDispatch
 
         path, params = generate(route_name, path_options, recall)
 
+        if options.key? :params
+          params.merge! options[:params]
+        end
+
         options[:path]        = path
         options[:script_name] = script_name
         options[:params]      = params

actionpack/lib/action_dispatch/routing/url_for.rb

@@ -133,6 +133,7 @@ module ActionDispatch
       #   <tt>ActionDispatch::Http::URL.tld_length</tt>, which in turn defaults to 1.
       # * <tt>:port</tt> - Optionally specify the port to connect to.
       # * <tt>:anchor</tt> - An anchor name to be appended to the path.
+      # * <tt>:params</tt> - The query parameters to be appended to the path.
       # * <tt>:trailing_slash</tt> - If true, adds a trailing slash, as in "/archive/2009/"
       # * <tt>:script_name</tt> - Specifies application path relative to domain root. If provided, prepends application path.
       #

actionpack/test/controller/base_test.rb

@@ -193,7 +193,7 @@ class UrlOptionsTest < ActionController::TestCase
       action: "home",
       controller: "pages",
       only_path: true,
-      token: "secret"
+      params: { "token" => "secret" }
     }
 
     assert_equal "/home?token=secret", rs.url_for(options)

actionpack/test/controller/url_for_test.rb

@@ -354,6 +354,14 @@ module AbstractController
         assert_equal({ p2: "Y2" }.to_query, params[1])
       end
 
+      def test_params_option
+        url = W.new.url_for(only_path: true, controller: "c", action: "a", params: { domain: "foo", id: "1" })
+        params = extract_params(url)
+        assert_equal("/c/a?domain=foo&id=1", url)
+        assert_equal({ domain: "foo" }.to_query, params[0])
+        assert_equal({ id: "1" }.to_query, params[1])
+      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)