Prevent deletion of pages with descendants that are attached to nodes

When a parent page is destroyed, its descendant pages are also destroyed via the nested set. If any of those descendants are attached to menu nodes, the node references become broken.
This adds a before_destroy check that prevents deletion when descendant pages still have menu node associations.

Author: kulturbande

app/models/alchemy/page.rb

@@ -135,6 +135,8 @@ class Page < BaseRecord
 
     has_many :page_ingredients, class_name: "Alchemy::Ingredients::Page", foreign_key: :related_object_id, dependent: :nullify
 
+    before_destroy :check_descendants_for_menu_nodes
+
     before_validation :set_language,
       if: -> { language.nil? }
 
@@ -611,5 +613,13 @@ def touch_nodes
       ids = node_ids + nodes.flat_map { |n| n.ancestors.pluck(:id) }
       Node.where(id: ids).touch_all
     end
+
+    def check_descendants_for_menu_nodes
+      pages_with_nodes = descendants.joins(:nodes).reorder("alchemy_pages.lft").distinct
+      if pages_with_nodes.exists?
+        errors.add(:descendants, :still_attached_to_nodes, page_names: pages_with_nodes.map(&:name).to_sentence)
+        throw :abort
+      end
+    end
   end
 end

config/locales/alchemy.en.yml

@@ -834,6 +834,8 @@ en:
             base:
               restrict_dependent_destroy:
                 has_many: "There are still %{record} attached to this page. Please remove them first."
+            descendants:
+              still_attached_to_nodes: "The following descendant pages are still attached to menu nodes: %{page_names}. Please remove them first."
         alchemy/element:
           attributes:
             page_version_id:

spec/models/alchemy/page_spec.rb

@@ -281,6 +281,22 @@ module Alchemy
             expect { page.destroy! }.to change { ingredient.reload.related_object_id }.from(page.id).to(nil)
           end
         end
+
+        context "with a descendant page attached to a menu node" do
+          let!(:page) { create(:alchemy_page) }
+          let!(:child_page) { create(:alchemy_page, parent: page) }
+          let!(:node) { create(:alchemy_node, page: child_page, parent: create(:alchemy_node)) }
+
+          it "prevents destruction of the parent page" do
+            expect(page.destroy).to be false
+            expect(page.errors[:descendants]).to include(
+              ::I18n.t(
+                "activerecord.errors.models.alchemy/page.attributes.descendants.still_attached_to_nodes",
+                page_names: child_page.name
+              )
+            )
+          end
+        end
       end
     end