Fix incorrect assert_redirected_to failure message

In some instances, `assert_redirected_to` assertion was returning an
incorrect and misleading failure message when the assertion failed.
This was due to a disconnect in how the assertion computes the redirect
string for the failure message and how `redirect_to` computes the
string that is actually used for redirection.

I made the `_compute_redirect_to_loaction` method used by `redirect_to`
public and call that from the method `assert_redirect_to` uses to
calculate the URL.

The reveals a new test failure due to the regex used by
`_compute_redirect_to_location` allow `_` in the URL scheme.

1 files changed, 18 insertions, 0 deletions

diff --git a/actionpack/test/controller/action_pack_assertions_test.rb b/actionpack/test/controller/action_pack_assertions_test.rb
index 22a410db94..ba4cffcd3e 100644
--- a/actionpack/test/controller/action_pack_assertions_test.rb
+++ b/actionpack/test/controller/action_pack_assertions_test.rb
@@ -39,6 +39,8 @@ class ActionPackAssertionsController < ActionController::Base
 
   def redirect_external() redirect_to "http://www.rubyonrails.org"; end
 
+  def redirect_external_protocol_relative() redirect_to "//www.rubyonrails.org"; end
+
   def response404() head '404 AWOL' end
 
   def response500() head '500 Sorry' end
@@ -258,6 +260,19 @@ class ActionPackAssertionsControllerTest < ActionController::TestCase
     end
   end
 
+  def test_assert_redirect_failure_message_with_protocol_relative_url
+    begin
+      process :redirect_external_protocol_relative
+      assert_redirected_to "/foo"
+    rescue ActiveSupport::TestCase::Assertion => ex
+      assert_no_match(
+        /#{request.protocol}#{request.host}\/\/www.rubyonrails.org/,
+        ex.message,
+        'protocol relative url was incorrectly normalized'
+      )
+    end
+  end
+
   def test_template_objects_exist
     process :assign_this
     assert !@controller.instance_variable_defined?(:"@hi")
@@ -309,6 +324,9 @@ class ActionPackAssertionsControllerTest < ActionController::TestCase
 
     process :redirect_external
     assert_equal 'http://www.rubyonrails.org', @response.redirect_url
+
+    process :redirect_external_protocol_relative
+    assert_equal '//www.rubyonrails.org', @response.redirect_url
   end
 
   def test_no_redirect_url