Fix nested multiple roots

The PR #20940 enabled the use of multiple roots with different constraints
at the top level but unfortunately didn't work when those roots were inside
a namespace and also broke the use of root inside a namespace after a top
level root was defined because the check for the existence of the named route
used the global :root name and not the namespaced name.

This is fixed by using the name_for_action method to expand the :root name to
the full namespaced name. We can pass nil for the second argument as we're not
dealing with resource definitions so don't need to handle the cases for edit
and new routes.

Fixes #26148.

1 files changed, 42 insertions, 0 deletions

diff --git a/actionpack/test/dispatch/routing_test.rb b/actionpack/test/dispatch/routing_test.rb
index ee5c30ef0e..0938460632 100644
--- a/actionpack/test/dispatch/routing_test.rb
+++ b/actionpack/test/dispatch/routing_test.rb
@@ -3669,6 +3669,48 @@ class TestRoutingMapper < ActionDispatch::IntegrationTest
     end
   end
 
+  def test_multiple_roots
+    draw do
+      namespace :foo do
+        root "pages#index", constraints: { host: 'www.example.com' }
+        root "admin/pages#index", constraints: { host: 'admin.example.com' }
+      end
+
+      root "pages#index", constraints: { host: 'www.example.com' }
+      root "admin/pages#index", constraints: { host: 'admin.example.com' }
+    end
+
+    get "http://www.example.com/foo"
+    assert_equal "foo/pages#index", @response.body
+
+    get "http://admin.example.com/foo"
+    assert_equal "foo/admin/pages#index", @response.body
+
+    get "http://www.example.com/"
+    assert_equal "pages#index", @response.body
+
+    get "http://admin.example.com/"
+    assert_equal "admin/pages#index", @response.body
+  end
+
+  def test_namespaced_roots
+    draw do
+      namespace :foo do
+        root "test#index"
+      end
+
+      root "test#index"
+
+      namespace :bar do
+        root "test#index"
+      end
+    end
+
+    assert_equal "/foo", foo_root_path
+    assert_equal "/", root_path
+    assert_equal "/bar", bar_root_path
+  end
+
 private
 
   def draw(&block)