Always use the provided port for protocol relative urls

There may be situations where you need to tunnel SSL connections over
port 80 so we shouldn't remove it if it has been explicitly provided.

3 files changed, 20 insertions, 0 deletions

diff --git a/actionpack/CHANGELOG.md b/actionpack/CHANGELOG.md
index d52ccd3d5e..5123713c6b 100644
--- a/actionpack/CHANGELOG.md
+++ b/actionpack/CHANGELOG.md
@@ -1,3 +1,9 @@
+*   Always use the provided port if the protocol is relative.
+
+    Fixes #15043.
+
+    *Guilherme Cavalcanti*, *Andrew White*
+
 *   Moved `params[request_forgery_protection_token]` into its own method
     and improved tests.
 
diff --git a/actionpack/lib/action_dispatch/http/url.rb b/actionpack/lib/action_dispatch/http/url.rb
index 77ea0cf658..c9860af909 100644
--- a/actionpack/lib/action_dispatch/http/url.rb
+++ b/actionpack/lib/action_dispatch/http/url.rb
@@ -135,6 +135,8 @@ module ActionDispatch
           return nil if options[:port].nil? || options[:port] == false
 
           case options[:protocol]
+          when "//"
+            options[:port]
           when "https://"
             options[:port].to_i == 443 ? nil : options[:port]
           else
diff --git a/actionpack/test/dispatch/url_generation_test.rb b/actionpack/test/dispatch/url_generation_test.rb
index fdea27e2d2..910ff8a80f 100644
--- a/actionpack/test/dispatch/url_generation_test.rb
+++ b/actionpack/test/dispatch/url_generation_test.rb
@@ -64,18 +64,30 @@ module TestUrlGeneration
 
     test "port is extracted from the host" do
       assert_equal "http://www.example.com:8080/foo", foo_url(host: "www.example.com:8080", protocol: "http://")
+      assert_equal "//www.example.com:8080/foo", foo_url(host: "www.example.com:8080", protocol: "//")
+      assert_equal "//www.example.com:80/foo", foo_url(host: "www.example.com:80", protocol: "//")
+    end
+
+    test "port option is used" do
+      assert_equal "http://www.example.com:8080/foo", foo_url(host: "www.example.com", protocol: "http://", port: 8080)
+      assert_equal "//www.example.com:8080/foo", foo_url(host: "www.example.com", protocol: "//", port: 8080)
+      assert_equal "//www.example.com:80/foo", foo_url(host: "www.example.com", protocol: "//", port: 80)
     end
 
     test "port option overrides the host" do
       assert_equal "http://www.example.com:8080/foo", foo_url(host: "www.example.com:8443", protocol: "http://", port: 8080)
+      assert_equal "//www.example.com:8080/foo", foo_url(host: "www.example.com:8443", protocol: "//", port: 8080)
+      assert_equal "//www.example.com:80/foo", foo_url(host: "www.example.com:443", protocol: "//", port: 80)
     end
 
     test "port option disables the host when set to nil" do
       assert_equal "http://www.example.com/foo", foo_url(host: "www.example.com:8443", protocol: "http://", port: nil)
+      assert_equal "//www.example.com/foo", foo_url(host: "www.example.com:8443", protocol: "//", port: nil)
     end
 
     test "port option disables the host when set to false" do
       assert_equal "http://www.example.com/foo", foo_url(host: "www.example.com:8443", protocol: "http://", port: false)
+      assert_equal "//www.example.com/foo", foo_url(host: "www.example.com:8443", protocol: "//", port: false)
     end
 
     test "keep subdomain when key is true" do