Allow sorting of issues with milestone_due_asc

in GraphQL

app/graphql/resolvers/issues_resolver.rb

@@ -52,7 +52,9 @@ module Resolvers
 
     type Types::IssueType, null: true
 
-    NON_STABLE_CURSOR_SORTS = %i[priority_asc priority_desc label_priority_asc label_priority_desc].freeze
+    NON_STABLE_CURSOR_SORTS = %i[priority_asc priority_desc
+                                 label_priority_asc label_priority_desc
+                                 milestone_due_asc milestone_due_desc].freeze
 
     def resolve(**args)
       # The project could have been loaded in batch by `BatchLoader`.

app/graphql/types/issuable_sort_enum.rb

@@ -9,5 +9,7 @@ module Types
     value 'PRIORITY_DESC', 'Priority by descending order', value: :priority_desc
     value 'LABEL_PRIORITY_ASC', 'Label priority by ascending order', value: :label_priority_asc
     value 'LABEL_PRIORITY_DESC', 'Label priority by descending order', value: :label_priority_desc
+    value 'MILESTONE_DUE_ASC', 'Milestone due date by ascending order', value: :milestone_due_asc
+    value 'MILESTONE_DUE_DESC', 'Milestone due date by descending order', value: :milestone_due_desc
   end
 end

changelogs/unreleased/38296-graphql-add-milestone_due_asc-sort-for-issuables.yml

+---
+title: GraphQL issue queries can now be sorted by milestone due date
+merge_request: 29992
+author:
+type: added

doc/api/graphql/reference/gitlab_schema.graphql

@@ -4677,6 +4677,16 @@ enum IssueSort {
   """
   LABEL_PRIORITY_DESC
 
+  """
+  Milestone due date by ascending order
+  """
+  MILESTONE_DUE_ASC
+
+  """
+  Milestone due date by descending order
+  """
+  MILESTONE_DUE_DESC
+
   """
   Priority by ascending order
   """

doc/api/graphql/reference/gitlab_schema.json

@@ -13272,6 +13272,18 @@
               "isDeprecated": false,
               "deprecationReason": null
             },
+            {
+              "name": "MILESTONE_DUE_ASC",
+              "description": "Milestone due date by ascending order",
+              "isDeprecated": false,
+              "deprecationReason": null
+            },
+            {
+              "name": "MILESTONE_DUE_DESC",
+              "description": "Milestone due date by descending order",
+              "isDeprecated": false,
+              "deprecationReason": null
+            },
             {
               "name": "DUE_DATE_ASC",
               "description": "Due date by ascending order",

spec/graphql/resolvers/issues_resolver_spec.rb

@@ -190,6 +190,23 @@ describe Resolvers::IssuesResolver do
             expect(resolve_issues(sort: :label_priority_desc).items).to eq([label_issue2, label_issue3, label_issue1, label_issue4])
           end
         end
+
+        context 'when sorting by milestone due date' do
+          let_it_be(:project) { create(:project) }
+          let_it_be(:early_milestone) { create(:milestone, project: project, due_date: 10.days.from_now) }
+          let_it_be(:late_milestone) { create(:milestone, project: project, due_date: 30.days.from_now) }
+          let_it_be(:milestone_issue1) { create(:issue, project: project) }
+          let_it_be(:milestone_issue2) { create(:issue, project: project, milestone: early_milestone) }
+          let_it_be(:milestone_issue3) { create(:issue, project: project, milestone: late_milestone) }
+
+          it 'sorts issues ascending' do
+            expect(resolve_issues(sort: :milestone_due_asc).items).to eq([milestone_issue2, milestone_issue3, milestone_issue1])
+          end
+
+          it 'sorts issues descending' do
+            expect(resolve_issues(sort: :milestone_due_desc).items).to eq([milestone_issue3, milestone_issue2, milestone_issue1])
+          end
+        end
       end
 
       it 'returns issues user can see' do

spec/graphql/types/issuable_sort_enum_spec.rb

@@ -6,6 +6,10 @@ describe Types::IssuableSortEnum do
   it { expect(described_class.graphql_name).to eq('IssuableSort') }
 
   it 'exposes all the existing issuable sort values' do
-    expect(described_class.values.keys).to include(*%w[PRIORITY_ASC PRIORITY_DESC])
+    expect(described_class.values.keys).to include(
+      *%w[PRIORITY_ASC PRIORITY_DESC
+          LABEL_PRIORITY_ASC LABEL_PRIORITY_DESC
+          MILESTONE_DUE_ASC MILESTONE_DUE_DESC
+         ])
   end
 end

spec/graphql/types/issue_sort_enum_spec.rb

@@ -9,7 +9,7 @@ describe GitlabSchema.types['IssueSort'] do
 
   it 'exposes all the existing issue sort values' do
     expect(described_class.values.keys).to include(
-      *%w[DUE_DATE_ASC DUE_DATE_DESC RELATIVE_POSITION_ASC LABEL_PRIORITY_ASC LABEL_PRIORITY_DESC]
+      *%w[DUE_DATE_ASC DUE_DATE_DESC RELATIVE_POSITION_ASC]
     )
   end
 end

spec/requests/api/graphql/project/issues_spec.rb

@@ -119,7 +119,21 @@ describe 'getting an issue list for a project' do
 
   describe 'sorting and pagination' do
     let(:start_cursor) { graphql_data['project']['issues']['pageInfo']['startCursor'] }
-    let(:end_cursor) { graphql_data['project']['issues']['pageInfo']['endCursor'] }
+    let(:end_cursor)   { graphql_data['project']['issues']['pageInfo']['endCursor'] }
+    let(:data_path)    { [:project, :issues] }
+
+    def pagination_query(params, page_info)
+      graphql_query_for(
+        'project',
+        { 'fullPath' => sort_project.full_path },
+        "issues(#{params}) { #{page_info} edges { node { iid dueDate } } }"
+      )
+    end
+
+    def pagination_results_data(data)
+      data.map { |issue| issue.dig('node', 'iid').to_i }
+    end
+
 
     context 'when sorting by due date' do
       let_it_be(:sort_project) { create(:project, :public) }
@@ -387,6 +401,31 @@ describe 'getting an issue list for a project' do
         end
       end
     end
+
+    context 'when sorting by milestone due date' do
+      let_it_be(:sort_project) { create(:project, :public) }
+      let_it_be(:early_milestone) { create(:milestone, project: sort_project, due_date: 10.days.from_now) }
+      let_it_be(:late_milestone) { create(:milestone, project: sort_project, due_date: 30.days.from_now) }
+      let_it_be(:milestone_issue1) { create(:issue, project: sort_project) }
+      let_it_be(:milestone_issue2) { create(:issue, project: sort_project, milestone: early_milestone) }
+      let_it_be(:milestone_issue3) { create(:issue, project: sort_project, milestone: late_milestone) }
+
+      context 'when ascending' do
+        it_behaves_like 'sorted paginated query' do
+          let(:sort_param)       { 'MILESTONE_DUE_ASC' }
+          let(:first_param)      { 2 }
+          let(:expected_results) { [milestone_issue2.iid, milestone_issue3.iid, milestone_issue1.iid] }
+        end
+      end
+
+      context 'when descending' do
+        it_behaves_like 'sorted paginated query' do
+          let(:sort_param)       { 'MILESTONE_DUE_DESC' }
+          let(:first_param)      { 2 }
+          let(:expected_results) { [milestone_issue3.iid, milestone_issue2.iid, milestone_issue1.iid] }
+        end
+      end
+    end
   end
 
   def grab_iids(data = issues_data)