Rename GroupHierarchy into ObjectHierarchy

- we now use the hierarchy class also for epics
- also rename supports_nested_groups? into supports_nested_objects?
  - move it to a concern
- add checks for epics

ee/app/controllers/groups/epic_links_controller.rb

@@ -4,6 +4,7 @@ class Groups::EpicLinksController < Groups::EpicsController
   include EpicRelations
 
   before_action :check_feature_flag!
+  before_action :check_nested_support!
 
   before_action do
     push_frontend_feature_flag(:epic_links)
@@ -32,4 +33,8 @@ class Groups::EpicLinksController < Groups::EpicsController
   def check_feature_flag!
     render_404 unless Feature.enabled?(:epic_links, group)
   end
+
+  def check_nested_support!
+    render_404 unless Epic.supports_nested_objects?
+  end
 end

ee/app/finders/geo/attachment_registry_finder.rb

@@ -108,10 +108,10 @@ module Geo
     def group_uploads
       namespace_ids =
         if current_node.selective_sync_by_namespaces?
-          Gitlab::GroupHierarchy.new(current_node.namespaces).base_and_descendants.select(:id)
+          Gitlab::ObjectHierarchy.new(current_node.namespaces).base_and_descendants.select(:id)
         elsif current_node.selective_sync_by_shards?
           leaf_groups = Namespace.where(id: current_node.projects.select(:namespace_id))
-          Gitlab::GroupHierarchy.new(leaf_groups).base_and_ancestors.select(:id)
+          Gitlab::ObjectHierarchy.new(leaf_groups).base_and_ancestors.select(:id)
         else
           Namespace.none
         end

ee/app/helpers/ee/issuables_helper.rb

@@ -21,6 +21,7 @@ module EE
       if parent.is_a?(Group)
         data[:issueLinksEndpoint] = group_epic_issues_path(parent, issuable)
         data[:epicLinksEndpoint] = group_epic_links_path(parent, issuable)
+        data[:subepicsSupported] = ::Epic.supports_nested_objects?
       end
 
       data

ee/app/models/ee/epic.rb

@@ -12,6 +12,7 @@ module EE
       include Referable
       include Awardable
       include LabelEventable
+      include Descendant
 
       enum state: { opened: 1, closed: 2 }
 
@@ -228,8 +229,7 @@ module EE
     end
 
     def hierarchy
-      ::Gitlab::GroupHierarchy
-        .new(self.class.where(id: id))
+      ::Gitlab::ObjectHierarchy.new(self.class.where(id: id))
     end
 
     # we don't support project epics for epics yet, planned in the future #4019

ee/app/models/ee/user.rb

@@ -186,7 +186,7 @@ module EE
         project_creation_levels << nil
       end
 
-      developer_groups_hierarchy = ::Gitlab::GroupHierarchy.new(developer_groups).base_and_descendants
+      developer_groups_hierarchy = ::Gitlab::ObjectHierarchy.new(developer_groups).base_and_descendants
       ::Group.where(id: developer_groups_hierarchy.select(:id),
                     project_creation_level: project_creation_levels)
     end

ee/app/models/geo_node.rb

@@ -187,7 +187,7 @@ class GeoNode < ActiveRecord::Base
     return Project.all unless selective_sync?
 
     if selective_sync_by_namespaces?
-      query = Gitlab::GroupHierarchy.new(namespaces).base_and_descendants
+      query = Gitlab::ObjectHierarchy.new(namespaces).base_and_descendants
       Project.where(namespace_id: query.select(:id))
     elsif selective_sync_by_shards?
       Project.where(repository_storage: selective_sync_shards)

ee/app/services/ee/ci/register_job_service.rb

@@ -52,7 +52,7 @@ module EE
         namespaces = ::Namespace.reorder(nil).where('namespaces.id = projects.namespace_id')
 
         if ::Feature.enabled?(:shared_runner_minutes_on_root_namespace)
-          namespaces = ::Gitlab::GroupHierarchy.new(namespaces).roots
+          namespaces = ::Gitlab::ObjectHierarchy.new(namespaces).roots
         end
 
         namespaces

ee/lib/gitlab/group_plans_preloader.rb

@@ -58,7 +58,7 @@ module Gitlab
     # Returns an ActiveRecord::Relation that includes the given groups, and all
     # their (recursive) ancestors.
     def groups_and_ancestors_for(groups)
-      Gitlab::GroupHierarchy
+      Gitlab::ObjectHierarchy
         .new(groups)
         .base_and_ancestors
         .select(:id, :parent_id, :plan_id)

ee/spec/controllers/groups/epic_links_controller_spec.rb

@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-describe Groups::EpicLinksController do
+describe Groups::EpicLinksController, :postgresql do
   let(:group) { create(:group, :public) }
   let(:parent_epic) { create(:epic, group: group) }
   let(:epic1) { create(:epic, group: group) }

ee/spec/models/namespace_spec.rb

@@ -188,7 +188,7 @@ describe Namespace do
           end
         end
 
-        if Group.supports_nested_groups?
+        if Group.supports_nested_objects?
           context 'when license is applied to parent group' do
             let(:child_group) { create :group, parent: group }
 

ee/spec/services/epic_links/create_service_spec.rb

@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-describe EpicLinks::CreateService, :nested_groups do
+describe EpicLinks::CreateService, :postgresql do
   describe '#execute' do
     let(:group) { create(:group) }
     let(:user) { create(:user) }

ee/spec/services/epic_links/list_service_spec.rb

@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-describe EpicLinks::ListService do
+describe EpicLinks::ListService, :postgresql do
   let(:user) { create :user }
   let(:group) { create(:group, :public) }
   let(:parent_epic) { create(:epic, group: group) }
@@ -51,7 +51,7 @@ describe EpicLinks::ListService do
         end
       end
 
-      context 'with nested groups', :nested_groups do
+      context 'with nested groups' do
         let(:subgroup1) { create(:group, :private, parent: group) }
         let(:subgroup2) { create(:group, :private, parent: group) }
         let!(:epic_subgroup1) { create :epic, group: subgroup1, parent: parent_epic }

lib/gitlab/object_hierarchy.rb

@@ -45,7 +45,7 @@ module Gitlab
     end
     # rubocop: enable CodeReuse/ActiveRecord
 
-    # Returns a relation that includes the ancestors_base set of groups
+    # Returns a relation that includes the ancestors_base set of objects
     # and all their ancestors (recursively).
     #
     # Passing an `upto` will stop the recursion once the specified parent_id is

spec/helpers/issuables_helper_spec.rb

@@ -220,7 +220,8 @@ describe IssuablesHelper do
         initialTitleText: epic.title,
         initialDescriptionHtml: '<p dir="auto">epic text</p>',
         initialDescriptionText: 'epic text',
-        initialTaskStatus: '0 of 0 tasks completed'
+        initialTaskStatus: '0 of 0 tasks completed',
+        subepicsSupported: Gitlab::Database.postgresql? ? true : false
       }
       expect(helper.issuable_initial_data(epic)).to eq(expected_data)
     end

spec/lib/gitlab/object_hierarchy_spec.rb

@@ -119,7 +119,7 @@ describe Gitlab::ObjectHierarchy, :postgresql do
     end
   end
 
-  describe '#all_groups' do
+  describe '#all_objects' do
     let(:relation) do
       described_class.new(Group.where(id: child1.id)).all_objects
     end