Fix scaffold index.html.erb variable name

Due to a conflict between #43846 and #43611, the variable name generated
inside the `each` block did not match the block parameter name for
namespaced models.  For example, if the block parameter name was
`admin_role`, the variable name inside the block would be just `role`.

This commit changes `index.html.erb` to use the correct variable name,
and adds much more test coverage.

This commit also changes the target for the "Destroy" button rendered
in `show.html.erb` from a route helper call to a bare model reference,
e.g. from `admin_role_path(@admin_role)` to just `@admin_role`.  This
was missed in #43611.

railties/lib/rails/generators/erb/scaffold/templates/index.html.erb.tt

@@ -6,7 +6,7 @@
   <%% @<%= plural_table_name %>.each do |<%= singular_table_name %>| %>
     <%%= render <%= singular_table_name %> %>
     <p>
-      <%%= link_to "Show this <%= human_name.downcase %>", <%= model_resource_name(singular_name) %> %>
+      <%%= link_to "Show this <%= human_name.downcase %>", <%= model_resource_name(singular_table_name) %> %>
     </p>
   <%% end %>
 </div>

railties/lib/rails/generators/erb/scaffold/templates/show.html.erb.tt

@@ -6,5 +6,5 @@
   <%%= link_to "Edit this <%= human_name.downcase %>", <%= edit_helper(type: :path) %> %> |
   <%%= link_to "Back to <%= human_name.pluralize.downcase %>", <%= index_helper(type: :path) %> %>
 
-  <%%= button_to "Destroy this <%= human_name.downcase %>", <%= show_helper(type: :path) %>, method: :delete %>
+  <%%= button_to "Destroy this <%= human_name.downcase %>", <%= model_resource_name(prefix: "@") %>, method: :delete %>
 </div>

railties/lib/rails/generators/named_base.rb

@@ -147,8 +147,8 @@ module Rails
           model_resource_name(prefix: "@")
         end
 
-        def model_resource_name(model = singular_table_name, prefix: "") # :doc:
-          resource_name = "#{prefix}#{model}"
+        def model_resource_name(base_name = singular_table_name, prefix: "") # :doc:
+          resource_name = "#{prefix}#{base_name}"
           if options[:model_name]
             "[#{controller_class_path.map { |name| ":" + name }.join(", ")}, #{resource_name}]"
           else

railties/test/generators/scaffold_controller_generator_test.rb

@@ -221,27 +221,37 @@ class ScaffoldControllerGeneratorTest < Rails::Generators::TestCase
     end
 
     assert_file "app/views/admin/users/index.html.erb" do |content|
-      assert_match(%{"New user", new_admin_user_path}, content)
-      assert_match(%{"Show this user", [:admin, user]}, content)
-    end
-
-    assert_file "app/views/admin/users/new.html.erb" do |content|
-      assert_match(%{"Back to users", admin_users_path}, content)
-    end
-
-    assert_file "app/views/admin/users/edit.html.erb" do |content|
-      assert_match(%{"Show this user", [:admin, @user]}, content)
-      assert_match(%{"Back to users", admin_users_path}, content)
+      assert_match %{@users.each do |user|}, content
+      assert_match %{render user}, content
+      assert_match %{"Show this user", [:admin, user]}, content
+      assert_match %{"New user", new_admin_user_path}, content
     end
 
     assert_file "app/views/admin/users/show.html.erb" do |content|
-      assert_match(%{"Edit this user", edit_admin_user_path(@user)}, content)
-      assert_match(%{"Back to users", admin_users_path}, content)
-      assert_match(%{"Destroy this user", admin_user_path(@user)}, content)
+      assert_match %{render @user}, content
+      assert_match %{"Edit this user", edit_admin_user_path(@user)}, content
+      assert_match %{"Back to users", admin_users_path}, content
+      assert_match %{"Destroy this user", [:admin, @user]}, content
+    end
+
+    assert_file "app/views/admin/users/_user.html.erb" do |content|
+      assert_match "user", content
+      assert_no_match "admin_user", content
+    end
+
+    assert_file "app/views/admin/users/new.html.erb" do |content|
+      assert_match %{render "form", user: @user}, content
+      assert_match %{"Back to users", admin_users_path}, content
+    end
+
+    assert_file "app/views/admin/users/edit.html.erb" do |content|
+      assert_match %{render "form", user: @user}, content
+      assert_match %{"Show this user", [:admin, @user]}, content
+      assert_match %{"Back to users", admin_users_path}, content
     end
 
     assert_file "app/views/admin/users/_form.html.erb" do |content|
-      assert_match("model: [:admin, user]", content)
+      assert_match %{model: [:admin, user]}, content
     end
 
     assert_file "test/controllers/admin/users_controller_test.rb" do |content|

railties/test/generators/scaffold_generator_test.rb

@@ -270,7 +270,17 @@ class ScaffoldGeneratorTest < Rails::Generators::TestCase
 
     # Views
     assert_file "app/views/admin/roles/index.html.erb" do |content|
-      assert_match(%("New role", new_admin_role_path), content)
+      assert_match %{@admin_roles.each do |admin_role|}, content
+      assert_match %{render admin_role}, content
+      assert_match %{"Show this role", admin_role}, content
+      assert_match %{"New role", new_admin_role_path}, content
+    end
+
+    assert_file "app/views/admin/roles/show.html.erb" do |content|
+      assert_match %{render @admin_role}, content
+      assert_match %{"Edit this role", edit_admin_role_path(@admin_role)}, content
+      assert_match %{"Back to roles", admin_roles_path}, content
+      assert_match %{"Destroy this role", @admin_role}, content
     end
 
     assert_file "app/views/admin/roles/_role.html.erb" do |content|
@@ -278,9 +288,21 @@ class ScaffoldGeneratorTest < Rails::Generators::TestCase
       assert_no_match "admin_role", content
     end
 
-    %w(edit new show _form).each do |view|
-      assert_file "app/views/admin/roles/#{view}.html.erb"
+    assert_file "app/views/admin/roles/new.html.erb"  do |content|
+      assert_match %{render "form", admin_role: @admin_role}, content
+      assert_match %{"Back to roles", admin_roles_path}, content
     end
+
+    assert_file "app/views/admin/roles/edit.html.erb" do |content|
+      assert_match %{render "form", admin_role: @admin_role}, content
+      assert_match %{"Show this role", @admin_role}, content
+      assert_match %{"Back to roles", admin_roles_path}, content
+    end
+
+    assert_file "app/views/admin/roles/_form.html.erb"  do |content|
+      assert_match %{model: admin_role}, content
+    end
+
     assert_no_file "app/views/layouts/admin/roles.html.erb"
 
     # Helpers