Check for adjacent_reference type

- and improve specs

ee/app/models/epic_issue.rb

@@ -10,6 +10,7 @@ class EpicIssue < ApplicationRecord
   belongs_to :issue
 
   alias_attribute :parent_ids, :epic_id
+  alias_attribute :parent, :epic
 
   scope :in_epic, ->(epic_id) { where(epic_id: epic_id) }
 end

ee/app/services/epics/tree_reorder_service.rb

@@ -39,11 +39,20 @@ module Epics
     end
 
     def validate_objects
-      unless moving_object.is_a?(EpicIssue) || moving_object.is_a?(Epic)
+      unless supported_type?(moving_object) && supported_type?(adjacent_reference)
         return 'Only epics and epic_issues are supported.'
       end
 
       return 'You don\'t have permissions to move the objects.' unless authorized?
+      return 'Both object have to belong to same parent epic.' unless same_parent?
+    end
+
+    def same_parent?
+      moving_object.parent == adjacent_reference.parent
+    end
+
+    def supported_type?(object)
+      object.is_a?(EpicIssue) || object.is_a?(Epic)
     end
 
     def authorized?

ee/spec/models/concerns/epic_tree_sorting_spec.rb

@@ -8,7 +8,6 @@ describe EpicTreeSorting do
   let!(:epic_issue1) { create(:epic_issue, epic: base_epic, relative_position: 10) }
   let!(:epic_issue2) { create(:epic_issue, epic: base_epic, relative_position: 500) }
   let!(:epic_issue3) { create(:epic_issue, epic: base_epic, relative_position: 1002) }
-  let!(:epic_issue4) { create(:epic_issue, epic: base_epic, relative_position: 1500) }
   let!(:epic1) { create(:epic, parent: base_epic, group: group, relative_position: 100) }
   let!(:epic2) { create(:epic, parent: base_epic, group: group, relative_position: 1000) }
   let!(:epic3) { create(:epic, parent: base_epic, group: group, relative_position: 1001) }

ee/spec/models/epic_issue_spec.rb

@@ -10,31 +10,4 @@ describe EpicIssue do
       let(:default_params) { { epic: epic } }
     end
   end
-
-  context 'relative positioning with 2 classes' do
-    let(:group) { create(:group) }
-    let(:base_epic) { create(:epic, group: group) }
-    let!(:epic_issue1) { create(:epic_issue, epic: base_epic, relative_position: 10) }
-    let!(:epic_issue2) { create(:epic_issue, epic: base_epic, relative_position: 50) }
-    let!(:epic_issue3) { create(:epic_issue, epic: base_epic, relative_position: 1500) }
-    let!(:epic1) { create(:epic, parent: base_epic, group: group, relative_position: 1000) }
-    let!(:epic2) { create(:epic, parent: base_epic, group: group, relative_position: 2000) }
-
-    context '#move_after' do
-      it 'moves the epic after an epic_issue' do
-        epic1.move_after(epic_issue3)
-
-        expect(epic1.relative_position).to be > epic_issue3.relative_position
-      end
-    end
-
-    context '#move_between' do
-      it 'moves the epic between epic_issues' do
-        epic1.move_between(epic_issue1, epic_issue2)
-
-        expect(epic1.relative_position).to be > epic_issue1.relative_position
-        expect(epic1.relative_position).to be < epic_issue2.relative_position
-      end
-    end
-  end
 end

ee/spec/requests/api/graphql/mutations/epic_tree/reorder_spec.rb

@@ -106,7 +106,7 @@ describe 'Updating an epic tree' do
           end
         end
 
-        context 'when moving an epic fails' do
+        context 'when moving an epic fails due another parent' do
           let(:epic2) { create(:epic, relative_position: 20) }
 
           it_behaves_like 'a mutation that does not update the tree'
@@ -114,7 +114,7 @@ describe 'Updating an epic tree' do
           it 'returns the error message' do
             post_graphql_mutation(mutation, current_user: current_user)
 
-            expect(mutation_response['errors']).to eq(['Epic not found for given params'])
+            expect(mutation_response['errors']).to eq(['Both object have to belong to same parent epic.'])
           end
         end
       end
@@ -138,7 +138,7 @@ describe 'Updating an epic tree' do
         end
       end
 
-      context 'when moving an issue fails' do
+      context 'when moving an issue fails due to another parent' do
         let(:epic_issue2) { create(:epic_issue, relative_position: 20) }
 
         before do
@@ -151,7 +151,7 @@ describe 'Updating an epic tree' do
         it 'returns the error message' do
           post_graphql_mutation(mutation, current_user: current_user)
 
-          expect(mutation_response['errors']).to eq(['Epic issue not found for given params'])
+          expect(mutation_response['errors']).to eq(['Both object have to belong to same parent epic.'])
         end
       end
     end

ee/spec/services/epics/tree_reorder_service_spec.rb

@@ -87,8 +87,22 @@ describe Epics::TreeReorderService do
             end
           end
 
+          context 'when object being moved is from of another epic' do
+            before do
+              other_epic = create(:epic, group: group)
+              epic_issue2.update(epic: other_epic)
+            end
+
+            it_behaves_like 'error for the tree update', 'Both object have to belong to same parent epic.'
+          end
+
           context 'when object being moved is not supported type' do
             let(:moving_object_id) { GitlabSchema.id_from_object(issue1) }
+
+            it_behaves_like 'error for the tree update', 'Only epics and epic_issues are supported.'
+          end
+
+          context 'when adjacent object is not supported type' do
             let(:adjacent_reference_id) { GitlabSchema.id_from_object(issue2) }
 
             it_behaves_like 'error for the tree update', 'Only epics and epic_issues are supported.'
@@ -131,6 +145,15 @@ describe Epics::TreeReorderService do
             it_behaves_like 'error for the tree update', 'You don\'t have permissions to move the objects.'
           end
 
+          context 'when object being moved is from of another epic' do
+            before do
+              other_epic = create(:epic, group: group)
+              epic2.update(parent: other_epic)
+            end
+
+            it_behaves_like 'error for the tree update', 'Both object have to belong to same parent epic.'
+          end
+
           context 'when moving is successful' do
             it 'updates the links relative positions' do
               subject