Allow issues to be sorted by relative_position

- adding a "Manual" option to the dropdown
- show 100 issues list when manually sorting

app/controllers/concerns/issuable_collections.rb

@@ -41,6 +41,7 @@ module IssuableCollections
     return if pagination_disabled?
 
     @issuables          = @issuables.page(params[:page])
+    @issuables          = per_page_for_relative_position if params[:sort] == 'relative_position'
     @issuable_meta_data = issuable_meta_data(@issuables, collection_type)
     @total_pages        = issuable_page_count
   end
@@ -80,6 +81,11 @@ module IssuableCollections
     (row_count.to_f / limit).ceil
   end
 
+  # manual / relative_position sorting allows for 100 items on the page
+  def per_page_for_relative_position
+    @issuables.per(100) # rubocop:disable Gitlab/ModuleWithInstanceVariables
+  end
+
   def issuable_finder_for(finder_class)
     finder_class.new(current_user, finder_options)
   end

app/helpers/sorting_helper.rb

@@ -25,7 +25,8 @@ module SortingHelper
       sort_value_popularity        => sort_title_popularity,
       sort_value_priority          => sort_title_priority,
       sort_value_upvotes           => sort_title_upvotes,
-      sort_value_contacted_date   => sort_title_contacted_date
+      sort_value_contacted_date    => sort_title_contacted_date,
+      sort_value_relative_position => sort_title_relative_position
     }
   end
 
@@ -397,6 +398,10 @@ module SortingHelper
     s_('SortOptions|Recent last activity')
   end
 
+  def sort_title_relative_position
+    s_('SortOptions|Manual')
+  end
+
   # Values.
   def sort_value_access_level_asc
     'access_level_asc'
@@ -545,4 +550,8 @@ module SortingHelper
   def sort_value_recently_last_activity
     'last_activity_on_desc'
   end
+
+  def sort_value_relative_position
+    'relative_position'
+  end
 end

app/models/issue.rb

@@ -58,6 +58,7 @@ class Issue < ApplicationRecord
   scope :order_due_date_asc, -> { reorder('issues.due_date IS NULL, issues.due_date ASC') }
   scope :order_due_date_desc, -> { reorder('issues.due_date IS NULL, issues.due_date DESC') }
   scope :order_closest_future_date, -> { reorder('CASE WHEN issues.due_date >= CURRENT_DATE THEN 0 ELSE 1 END ASC, ABS(CURRENT_DATE - issues.due_date) ASC') }
+  scope :order_relative_position_asc, -> { reorder(::Gitlab::Database.nulls_last_order('relative_position', 'ASC')) }
 
   scope :preload_associations, -> { preload(:labels, project: :namespace) }
   scope :with_api_entity_associations, -> { preload(:timelogs, :assignees, :author, :notes, :labels, project: [:route, { namespace: :route }] ) }
@@ -133,6 +134,7 @@ class Issue < ApplicationRecord
     when 'due_date'            then order_due_date_asc
     when 'due_date_asc'        then order_due_date_asc
     when 'due_date_desc'       then order_due_date_desc
+    when 'relative_position'   then order_relative_position_asc
     else
       super
     end

app/views/shared/issuable/_sort_dropdown.html.haml

@@ -17,5 +17,6 @@
           = sortable_item(sort_title_due_date,          page_filter_path(sort: sort_value_due_date),          sort_title) if viewing_issues
           = sortable_item(sort_title_popularity,        page_filter_path(sort: sort_value_popularity),        sort_title)
           = sortable_item(sort_title_label_priority,    page_filter_path(sort: sort_value_label_priority),    sort_title)
+          = sortable_item(sort_title_relative_position, page_filter_path(sort: sort_value_relative_position), sort_title) if viewing_issues
           = render_if_exists('shared/ee/issuable/sort_dropdown', viewing_issues: viewing_issues, sort_title: sort_title)
     = issuable_sort_direction_button(sort_value)

changelogs/unreleased/9121-sort-relative-position.yml

+---
+title: Allow issue list to be sorted by relative order
+merge_request: 28566
+author:
+type: added

locale/gitlab.pot

@@ -9061,6 +9061,9 @@ msgstr ""
 msgid "SortOptions|Least popular"
 msgstr ""
 
+msgid "SortOptions|Manual"
+msgstr ""
+
 msgid "SortOptions|Milestone due date"
 msgstr ""
 

spec/controllers/projects/issues_controller_spec.rb

@@ -130,6 +130,37 @@ describe Projects::IssuesController do
       end
     end
 
+    context 'with relative_position sorting' do
+      let!(:issue_list) { create_list(:issue, 2, project: project) }
+
+      before do
+        sign_in(user)
+        project.add_developer(user)
+        allow(Kaminari.config).to receive(:default_per_page).and_return(1)
+      end
+
+      it 'overrides the number allowed on the page' do
+        get :index,
+          params: {
+            namespace_id: project.namespace.to_param,
+            project_id:   project,
+            sort:         'relative_position'
+          }
+
+        expect(assigns(:issues).count).to eq 2
+      end
+
+      it 'allows the default number on the page' do
+        get :index,
+          params: {
+            namespace_id: project.namespace.to_param,
+            project_id:   project
+          }
+
+        expect(assigns(:issues).count).to eq 1
+      end
+    end
+
     context 'external authorization' do
       before do
         sign_in user

spec/models/issue_spec.rb

@@ -93,6 +93,21 @@ describe Issue do
     end
   end
 
+  describe '#sort' do
+    let(:project) { create(:project) }
+
+    context "by relative_position" do
+      let!(:issue)  { create(:issue, project: project) }
+      let!(:issue2) { create(:issue, project: project, relative_position: 2) }
+      let!(:issue3) { create(:issue, project: project, relative_position: 1) }
+
+      it "sorts asc with nulls at the end" do
+        issues = project.issues.sort_by_attribute('relative_position')
+        expect(issues).to eq([issue3, issue2, issue])
+      end
+    end
+  end
+
   describe '#card_attributes' do
     it 'includes the author name' do
       allow(subject).to receive(:author).and_return(double(name: 'Robert'))