Simplify

app/helpers/administrate/application_helper.rb

@@ -36,18 +36,11 @@ def model_from_resource(resource_name)
     #   - Class: resource class
     #   - ActiveRecord::Base: resource instance
     def administrate_valid_action?(target, action_name)
-      begin
-        target = target.to_s.classify.constantize if target.is_a?(String)
-        target_class = target.is_a?(ActiveRecord::Base) ? target.class : target
-      rescue NameError
-        # If target is a string, Pundit.policy! will try
-        # to use `StringPolicy`, which doesn't exist.
-        # If target is a symbol, Pundit.policy! will try
-        # to use `#{symbol}Policy`, which is correct.
-        target = target.to_sym
-      end
+      target = target.to_sym if target.is_a?(String)
+      target_class_or_class_name =
+        target.is_a?(ActiveRecord::Base) ? target.class : target
 
-      valid_action?(action_name, target_class) &&
+      valid_action?(action_name, target_class_or_class_name) &&
         show_action?(action_name, target)
     end
 

app/views/administrate/application/_navigation.html.erb

@@ -15,6 +15,6 @@ as defined by the routes in the `admin/` namespace
       display_resource_name(resource),
       resource_index_route(resource),
       class: "navigation__link navigation__link--#{nav_link_state(resource)}"
-    ) if administrate_valid_action?(resource, :index) %>
+    ) if administrate_valid_action?(resource.singularize, :index) %>
   <% end %>
 </nav>

spec/helpers/administrate/application_helper_spec.rb

@@ -109,10 +109,10 @@ class TestCustomResource; end
         ctx = double(valid_action?: true, show_action?: true)
         ctx.extend(Administrate::ApplicationHelper)
 
-        result = ctx.administrate_valid_action?("test_custom_resource", "foo")
+        ctx.administrate_valid_action?("test_custom_resource", "foo")
 
-        expect(ctx).to have_received(:valid_action?).with("foo", TestCustomResource)
-        expect(ctx).to have_received(:show_action?).with("foo", TestCustomResource)
+        expect(ctx).to have_received(:valid_action?).with("foo", :test_custom_resource)
+        expect(ctx).to have_received(:show_action?).with("foo", :test_custom_resource)
       ensure
         remove_constants :TestCustomResource
       end
@@ -126,7 +126,6 @@ class TestCustomResource; end
 
         ctx.administrate_valid_action?(:test_custom_resource, "foo")
 
-        # Using a symbol instead of a class is allowed for both methods
         expect(ctx).to have_received(:valid_action?).with("foo", :test_custom_resource)
         expect(ctx).to have_received(:show_action?).with("foo", :test_custom_resource)
       ensure