1 files changed, 13 insertions, 6 deletions

diff --git a/app/models/work_items/parent_link.rb b/app/models/work_items/parent_link.rb
index 3c405dbce3b..f5ebbfa59b8 100644
--- a/app/models/work_items/parent_link.rb
+++ b/app/models/work_items/parent_link.rb
@@ -5,11 +5,13 @@ module WorkItems
     self.table_name = 'work_item_parent_links'
 
     MAX_CHILDREN = 100
+    PARENT_TYPES = [:issue, :incident].freeze
 
     belongs_to :work_item
     belongs_to :work_item_parent, class_name: 'WorkItem'
 
-    validates :work_item, :work_item_parent, presence: true
+    validates :work_item_parent, presence: true
+    validates :work_item, presence: true, uniqueness: true
     validate :validate_child_type
     validate :validate_parent_type
     validate :validate_same_project
@@ -21,15 +23,20 @@ module WorkItems
       return unless work_item
 
       unless work_item.task?
-        errors.add :work_item, _('Only Task can be assigned as a child in hierarchy.')
+        errors.add :work_item, _('only Task can be assigned as a child in hierarchy.')
       end
     end
 
     def validate_parent_type
       return unless work_item_parent
 
-      unless work_item_parent.issue?
-        errors.add :work_item_parent, _('Only Issue can be parent of Task.')
+      base_type = work_item_parent.work_item_type.base_type.to_sym
+      unless PARENT_TYPES.include?(base_type)
+        parent_names = WorkItems::Type::BASE_TYPES.slice(*WorkItems::ParentLink::PARENT_TYPES)
+          .values.map { |type| type[:name] }
+
+        errors.add :work_item_parent, _('only %{parent_types} can be parent of Task.') %
+                                        { parent_types: parent_names.to_sentence }
       end
     end
 
@@ -37,7 +44,7 @@ module WorkItems
       return if work_item.nil? || work_item_parent.nil?
 
       if work_item.resource_parent != work_item_parent.resource_parent
-        errors.add :work_item_parent, _('Parent must be in the same project as child.')
+        errors.add :work_item_parent, _('parent must be in the same project as child.')
       end
     end
 
@@ -46,7 +53,7 @@ module WorkItems
 
       max = persisted? ? MAX_CHILDREN : MAX_CHILDREN - 1
       if work_item_parent.child_links.count > max
-        errors.add :work_item_parent, _('Parent already has maximum number of children.')
+        errors.add :work_item_parent, _('parent already has maximum number of children.')
       end
     end
   end