Fallback to RAILS_RELATIVE_URL_ROOT in `url_for`.

Fixed an issue where the `RAILS_RELATIVE_URL_ROOT` environment
variable is not prepended to the path when `url_for` is called.
If `SCRIPT_NAME` (used by Rack) is set, it takes precedence.

4 files changed, 25 insertions, 1 deletions

diff --git a/actionpack/CHANGELOG.md b/actionpack/CHANGELOG.md
index 8685cd6495..a9e943bdc2 100644
--- a/actionpack/CHANGELOG.md
+++ b/actionpack/CHANGELOG.md
@@ -1,3 +1,13 @@
+*   Fallback to `ENV['RAILS_RELATIVE_URL_ROOT']` in `url_for`.
+
+    Fixed an issue where the `RAILS_RELATIVE_URL_ROOT` environment variable is not
+    prepended to the path when `url_for` is called. If `SCRIPT_NAME` (used by Rack)
+    is set, it takes precedence.
+
+    Fixes #5122.
+
+    *Yasyf Mohamedali*
+
 *   Deprecate AbstractController#skip_action_callback in favor of individual skip_callback methods
     (which can be made to raise an error if no callback was removed).
 
diff --git a/actionpack/lib/action_dispatch/railtie.rb b/actionpack/lib/action_dispatch/railtie.rb
index ddeea24bb3..8cde5eb6f7 100644
--- a/actionpack/lib/action_dispatch/railtie.rb
+++ b/actionpack/lib/action_dispatch/railtie.rb
@@ -40,6 +40,8 @@ module ActionDispatch
       ActionDispatch::Cookies::CookieJar.always_write_cookie = config.action_dispatch.always_write_cookie
 
       ActionDispatch.test_app = app
+
+      ActionDispatch::Routing::RouteSet.relative_url_root = app.config.relative_url_root
     end
   end
 end
diff --git a/actionpack/lib/action_dispatch/routing/route_set.rb b/actionpack/lib/action_dispatch/routing/route_set.rb
index ce04f0b08a..da6a00304c 100644
--- a/actionpack/lib/action_dispatch/routing/route_set.rb
+++ b/actionpack/lib/action_dispatch/routing/route_set.rb
@@ -20,6 +20,8 @@ module ActionDispatch
       # alias inspect to to_s.
       alias inspect to_s
 
+      mattr_accessor :relative_url_root
+
       class Dispatcher < Routing::Endpoint
         def initialize(defaults)
           @defaults = defaults
@@ -693,7 +695,7 @@ module ActionDispatch
       end
 
       def find_script_name(options)
-        options.delete(:script_name) || ''
+        options.delete(:script_name) || relative_url_root || ''
       end
 
       def path_for(options, route_name = nil)
diff --git a/actionpack/test/controller/url_for_test.rb b/actionpack/test/controller/url_for_test.rb
index 0ffa2d2a03..cd63493b32 100644
--- a/actionpack/test/controller/url_for_test.rb
+++ b/actionpack/test/controller/url_for_test.rb
@@ -255,6 +255,16 @@ module AbstractController
         )
       end
 
+      def test_relative_url_root_is_respected_with_environment_variable
+        # `config.relative_url_root` is set by ENV['RAILS_RELATIVE_URL_ROOT']
+        ActionDispatch::Routing::RouteSet.relative_url_root = '/subdir'
+        add_host!
+        assert_equal('https://www.basecamphq.com/subdir/c/a/i',
+          W.new.url_for(:controller => 'c', :action => 'a', :id => 'i', :protocol => 'https')
+        )
+        ActionDispatch::Routing::RouteSet.relative_url_root = nil
+      end
+
       def test_named_routes
         with_routing do |set|
           set.draw do