[wip] Do not use '@ record' to indicate custom button screen

'@ record' is set while rendering the page, but after button click, the '@ record' is nil.

The id in params[:id] is providers id

app/controllers/application_controller/buttons.rb

@@ -296,8 +296,19 @@ def custom_buttons(ids = nil, display_options = {})
     button = CustomButton.find(params[:button_id])
     cls = custom_button_class_model(button.applies_to_class)
     @explorer = true if BASE_MODEL_EXPLORER_CLASSES.include?(cls)
-    ids ||= params[:id]
-    if ids.to_s == 'LIST'
+    ids ||= params[:id] unless relationship_table_screen? && @record.nil?
+    ids ||= find_checked_items # FIXME: for some reason, this doesn't work
+
+
+    binding.pry
+
+    # FIXME: copypasted from below
+    if ids.empty?
+      render_flash(_("Error executing custom button: No item was selected."), :error)
+      return
+    end
+
+    if ids.to_s == 'LIST' || !ids.empty?
       objs = Rbac.filtered(cls.where(:id => find_checked_items))
       obj = objs.first
     else

app/helpers/application_helper/toolbar/mixins/custom_button_toolbar_mixin.rb

@@ -28,22 +28,21 @@ def custom_button_class_model(applies_to_class)
   end
 
   # Indicates, whether the user has came from providers relationship screen
-  # or not
+  # or not, before the page is rendered
   #
   # Used to indicate if the custom buttons should be rendered
   def relationship_table_screen?
-    return false if @display.nil? || @record.nil?
+    return false if @display.nil?
+    display_class = @display.camelize.singularize
+    return false unless custom_button_appliable_class?(display_class)
 
-    display_model = @display.camelize.singularize
-    providers = (EmsCloud.descendants +
-                 EmsInfra.descendants +
-                 EmsPhysicalInfra.descendants +
-                 ManageIQ::Providers::ContainerManager.descendants)
-
-    custom_button_model = custom_button_appliable_class?(display_model)
-    provider_screen = providers.any? { |provider| @record.instance_of?(provider) }
     show_action = @lastaction == "show"
+    display_model = display_class.constantize
+    # method is accessed twice from a different location - from toolbar builder
+    # and custom button mixin - and so controller class changes
+    ctrl = self.class == ApplicationHelper::ToolbarBuilder ? controller : self
+    controller_model = ctrl.class.model
 
-    custom_button_model && provider_screen && show_action
+    display_model != controller_model && show_action
   end
 end