Use children rather than child_ids

- Direct children

ee/app/graphql/types/epic_type.rb

@@ -138,11 +138,5 @@ module Types
       resolve: -> (epic, args, ctx) do
         Gitlab::Graphql::Aggregations::Epics::LazyEpicAggregate.new(ctx, epic.id, WEIGHT_SUM)
       end
-
-    field :health_status,
-      ::Types::HealthStatusEnum,
-      null: true,
-      description: 'Current health status',
-      feature_flag: :save_issuable_health_status
   end
 end

ee/lib/gitlab/graphql/aggregations/epics/epic_node.rb

@@ -14,7 +14,7 @@ module Gitlab
                       :direct_count_totals, :direct_weight_sum_totals, # only counts/weights of direct issues and child epic counts
                       :count_aggregate, :weight_sum_aggregate
 
-          attr_accessor :child_ids, :calculated_count_totals, :calculated_weight_sum_totals
+          attr_accessor :children, :calculated_count_totals, :calculated_weight_sum_totals
 
           def initialize(epic_id, flat_info_list)
             # epic aggregate records from the DB loader look like the following:
@@ -23,7 +23,7 @@ module Gitlab
             # so in order to get a sum of the entire tree, we have to add that up recursively
             @epic_id = epic_id
             @epic_info_flat_list = flat_info_list
-            @child_ids = []
+            @children = []
             @direct_count_totals = []
             @direct_weight_sum_totals = []
 
@@ -43,7 +43,7 @@ module Gitlab
             end
           end
 
-          def assemble_epic_totals(children)
+          def assemble_epic_totals
             [OPENED_EPIC_STATE, CLOSED_EPIC_STATE].each do |epic_state|
               create_sum_if_needed(COUNT, epic_state, EPIC_TYPE, children.select { |node| node.epic_state_id == epic_state }.count)
             end
@@ -91,9 +91,7 @@ module Gitlab
             return calculated_totals(facet) if calculated_totals(facet)
 
             sum_total = []
-            child_ids.each do |child_id|
-              child = tree[child_id]
-              # get the child's totals, add to your own
+            children.each do |child|
               child_sums = child.calculate_recursive_sums(facet, tree)
               sum_total.concat(child_sums)
             end
@@ -101,6 +99,19 @@ module Gitlab
             set_calculated_total(facet, sum_total)
           end
 
+          def inspect
+            {
+                epic_id: @epic_id,
+                parent_id: @parent_id,
+                direct_count_totals: direct_count_totals,
+                direct_weight_sum_totals: direct_weight_sum_totals,
+                children: children,
+                object_id: object_id
+            }.to_json
+          end
+
+          alias_method :to_s, :inspect
+
           private
 
           def sum_objects(facet, state, type)

ee/lib/gitlab/graphql/aggregations/epics/lazy_epic_aggregate.rb

@@ -87,10 +87,14 @@ module Gitlab
 
           def assemble_direct_child_totals
             tree.each do |_, node|
-              node_children = tree.select { |_, child_node| node.epic_id == child_node.parent_id }
-              node.child_ids = node_children.keys
-              node.assemble_epic_totals(node_children.values)
+              parent = tree[node.parent_id]
+              next if parent.nil?
 
+              parent.children << node
+            end
+
+            tree.each do |_, node|
+              node.assemble_epic_totals
               node.assemble_issue_totals
             end
           end

ee/spec/graphql/types/epic_type_spec.rb

@@ -11,7 +11,7 @@ describe GitlabSchema.types['Epic'] do
       closed_at created_at updated_at children has_children has_issues
       web_path web_url relation_path reference issues user_permissions
       notes discussions relative_position subscribed participants
-      descendant_counts descendant_weight_sum upvotes downvotes health_status
+      descendant_counts descendant_weight_sum upvotes downvotes
     ]
   end
 

ee/spec/lib/gitlab/graphql/aggregations/epics/epic_node_spec.rb

@@ -110,11 +110,11 @@ describe Gitlab::Graphql::Aggregations::Epics::EpicNode do
       let!(:child_epic_node) { described_class.new(child_epic_id, [{ parent_id: epic_id, epic_state_id: CLOSED_EPIC_STATE }]) }
 
       before do
-        subject.child_ids << child_epic_id
+        subject.children << child_epic_node
       end
 
       it 'adds up the number of the child epics' do
-        subject.assemble_epic_totals([child_epic_node])
+        subject.assemble_epic_totals
 
         expect(subject).to have_direct_total(EPIC_TYPE, COUNT_FACET, CLOSED_EPIC_STATE, 1)
       end
@@ -191,7 +191,7 @@ describe Gitlab::Graphql::Aggregations::Epics::EpicNode do
       let(:immediate_weight_sum_totals) { [] }
 
       before do
-        subject.child_ids << child_epic_id
+        subject.children << child_epic_node
         allow(child_epic_node).to receive(:direct_totals).with(COUNT_FACET).and_return(child_count_totals)
         allow(child_epic_node).to receive(:direct_totals).with(WEIGHT_SUM_FACET).and_return(child_weight_sum_totals)
       end

ee/spec/lib/gitlab/graphql/aggregations/epics/lazy_epic_aggregate_spec.rb

@@ -98,7 +98,7 @@ describe Gitlab::Graphql::Aggregations::Epics::LazyEpicAggregate do
         tree = lazy_state[:tree]
 
         expect(tree[child_epic_id].parent_id).to eq epic_id
-        expect(tree[epic_id].child_ids).to match_array([child_epic_id])
+        expect(tree[epic_id].children.map(&:epic_id)).to match_array([child_epic_id])
       end
 
       context 'for a parent-child relationship' do