1 files changed, 58 insertions, 0 deletions
diff --git a/app/graphql/resolvers/work_items/ancestors_resolver.rb b/app/graphql/resolvers/work_items/ancestors_resolver.rb
new file mode 100644
index 00000000000..33adbfc9c86
--- /dev/null
+++ b/app/graphql/resolvers/work_items/ancestors_resolver.rb
@@ -0,0 +1,58 @@
+# frozen_string_literal: true
+
+module Resolvers
+  module WorkItems
+    class AncestorsResolver < BaseResolver
+      prepend ::WorkItems::LookAheadPreloads
+
+      type Types::WorkItemType.connection_type, null: true
+
+      def resolve_with_lookahead
+        ancestors = object.ancestors
+        return WorkItem.none unless ancestors
+
+        truncate_ancestors(apply_lookahead(ancestors)).reverse!
+      end
+
+      private
+
+      def truncate_ancestors(ancestors)
+        # Iterate from closest ancestor until root or first missing ancestor
+        authorized = authorized_ancestors(ancestors)
+
+        previous_ancestor = object.work_item
+        authorized.take_while do |ancestor|
+          is_direct_parent = previous_ancestor.work_item_parent.id == ancestor.id
+          previous_ancestor = ancestor
+
+          is_direct_parent
+        end
+      end
+
+      def authorized_ancestors(ancestors)
+        preload_resource_parents(ancestors)
+
+        DeclarativePolicy.user_scope do
+          ancestors.select { |ancestor| Ability.allowed?(current_user, :read_work_item, ancestor) }
+        end
+      end
+
+      def preload_resource_parents(work_items)
+        projects = work_items.filter_map(&:project)
+        namespaces = work_items.filter_map(&:namespace)
+        group_namespaces = namespaces.select { |n| n.type == ::Group.sti_name }
+
+        ::Preloaders::GroupPolicyPreloader.new(group_namespaces, current_user).execute if group_namespaces.any?
+        return unless projects.any?
+
+        ::Preloaders::UserMaxAccessLevelInProjectsPreloader.new(projects, current_user).execute
+        ::Preloaders::GroupPolicyPreloader.new(projects.filter_map(&:namespace), current_user).execute
+        ActiveRecord::Associations::Preloader.new(records: projects, associations: [:namespace]).call
+      end
+
+      def unconditional_includes
+        [:namespace, :work_item_parent, :work_item_type]
+      end
+    end
+  end
+end