display empty array when not having ancestors

db/migrate/20220223095355_projects_lft_rgt_index.rb

@@ -1,5 +1,5 @@
 class ProjectsLftRgtIndex < ActiveRecord::Migration[6.1]
   def change
-    add_index :projects, %i[lft rgt], unique: true
+    add_index :projects, %i[lft rgt]
   end
 end

lib/api/v3/projects/project_sql_representer.rb

@@ -42,17 +42,27 @@ module API
           protected
 
           def ancestors_sql(walker_result)
+            origin_subselect = if walker_result.page_size
+                                 walker_result.filter_scope.limit(walker_result.page_size).offset((walker_result.offset - 1) * walker_result.page_size)
+                               else
+                                 walker_result.filter_scope
+                               end
+
             <<-SQL.squish
-              SELECT id, json_agg(link) ancestors
+              SELECT id, CASE WHEN count(link) = 0 THEN '[]' ELSE json_agg(link) END ancestors
               FROM
                 (
                   SELECT
                     origin.id,
-                    json_build_object('href', format('/api/v3/projects/%s', ancestors.id), 'title', ancestors.name) link
+                    CASE
+                      WHEN ancestors.id IS NOT NULL
+                        THEN json_build_object('href', format('/api/v3/projects/%s', ancestors.id), 'title', ancestors.name)
+                      ELSE NULL
+                    END link
                   FROM projects origin
-                  JOIN projects ancestors
+                  LEFT OUTER JOIN projects ancestors
                   ON ancestors.lft < origin.lft AND ancestors.rgt > origin.rgt
-                  WHERE origin.id IN (#{walker_result.filter_scope.limit(walker_result.page_size).offset((walker_result.offset - 1) * walker_result.page_size).select(:id).to_sql})
+                  WHERE origin.id IN (#{origin_subselect.select(:id).to_sql})
                   ORDER by origin.id, ancestors.lft
                 ) ancestors
               GROUP BY id

lib/api/v3/utilities/sql_walker_results.rb

@@ -34,7 +34,7 @@ module API
       class SqlWalkerResults
         def initialize(scope, url_query:, self_path: nil, replace_map: {})
           self.filter_scope = scope.dup
-          self.projection_scope = scope.dup.reselect("#{scope.model.table_name}.*")
+          self.projection_scope = scope.dup.distinct(false).reselect("#{scope.model.table_name}.*")
           self.ctes = {}
           self.self_path = self_path
           self.url_query = url_query

spec/lib/api/v3/capabilities/capability_sql_representer_rendering_spec.rb

@@ -62,7 +62,7 @@ describe ::API::V3::Capabilities::CapabilitySqlRepresenter, 'rendering' do
            embed: {},
            select: { 'id' => {}, '_type' => {}, 'self' => {}, 'action' => {}, 'context' => {}, 'principal' => {} },
            current_user: current_user)
-      .walk(API::V3::Capabilities::CapabilitySqlRepresenter)
+      .walk(described_class)
       .to_json
   end
 

spec/lib/api/v3/projects/project_sql_representer_renderning_spec.rb

@@ -0,0 +1,116 @@
+#  OpenProject is an open source project management software.
+#  Copyright (C) 2010-2022 the OpenProject GmbH
+#
+#  This program is free software; you can redistribute it and/or
+#  modify it under the terms of the GNU General Public License version 3.
+#
+#  OpenProject is a fork of ChiliProject, which is a fork of Redmine. The copyright follows:
+#  Copyright (C) 2006-2013 Jean-Philippe Lang
+#  Copyright (C) 2010-2013 the ChiliProject Team
+#
+#  This program is free software; you can redistribute it and/or
+#  modify it under the terms of the GNU General Public License
+#  as published by the Free Software Foundation; either version 2
+#  of the License, or (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program; if not, write to the Free Software
+#  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+#
+#  See COPYRIGHT and LICENSE files for more details.
+
+require 'spec_helper'
+
+describe ::API::V3::Projects::ProjectSqlRepresenter, 'rendering' do
+  include ::API::V3::Utilities::PathHelper
+
+  let(:scope) do
+    Project
+      .where(id: project.id)
+  end
+  let(:project) do
+    create(:project)
+  end
+
+  current_user do
+    create(:user,
+           member_in_project: project,
+           member_with_permissions: [])
+  end
+
+  subject(:json) do
+    ::API::V3::Utilities::SqlRepresenterWalker
+      .new(scope,
+           embed: {},
+           select: { 'id' => {}, '_type' => {}, 'self' => {}, 'name' => {}, 'ancestors' => {} },
+           current_user: current_user)
+      .walk(described_class)
+      .to_json
+  end
+
+  context 'without an ancestor' do
+    it 'renders as expected' do
+      expect(json)
+        .to be_json_eql(
+          {
+            id: project.id,
+            _type: "Project",
+            name: project.name,
+            _links: {
+              ancestors: [],
+              self: {
+                href: api_v3_paths.project(project.id),
+                title: project.name
+              }
+            }
+          }.to_json)
+    end
+  end
+
+  context 'with an ancestor' do
+    let!(:parent) do
+      create(:project).tap do |parent|
+        project.parent = parent
+        project.save
+      end
+    end
+
+    let!(:grandparent) do
+      create(:project).tap do |grandparent|
+        parent.parent = grandparent
+        parent.save
+      end
+    end
+
+    it 'renders as expected' do
+      expect(json)
+        .to be_json_eql(
+          {
+            id: project.id,
+            _type: "Project",
+            name: project.name,
+            _links: {
+              ancestors: [
+                {
+                  href: api_v3_paths.project(grandparent.id),
+                  title: grandparent.name
+                },
+                {
+                  href: api_v3_paths.project(parent.id),
+                  title: parent.name
+                }
+              ],
+              self: {
+                href: api_v3_paths.project(project.id),
+                title: project.name
+              }
+            }
+          }.to_json)
+    end
+  end
+end

spec/requests/api/v3/projects/index_resource_spec.rb

@@ -42,6 +42,12 @@ describe 'API v3 Project resource index', type: :request, content_type: :json do
   let(:other_project) do
     create(:project, public: false)
   end
+  let(:parent_project) do
+    create(:project, public: false, members: { current_user => role }).tap do |parent|
+      project.parent = parent
+      project.save
+    end
+  end
   let(:role) { create(:role) }
   let(:filters) { [] }
   let(:get_path) do
@@ -83,14 +89,6 @@ describe 'API v3 Project resource index', type: :request, content_type: :json do
   context 'when filtering for project by ancestor' do
     let(:projects) { [project, other_project, parent_project] }
 
-    let(:parent_project) do
-      parent_project = create(:project, public: false, members: { current_user => role })
-
-      project.update_attribute(:parent_id, parent_project.id)
-
-      parent_project
-    end
-
     let(:filters) do
       [{ ancestor: { operator: '=', values: [parent_project.id.to_s] } }]
     end
@@ -228,24 +226,39 @@ describe 'API v3 Project resource index', type: :request, content_type: :json do
   end
 
   context 'when signaling the properties to include' do
-    let(:projects) { [project] }
-    let(:select) { 'elements/id,elements/name' }
+    let(:projects) { [project, parent_project] }
+    let(:select) { 'elements/id,elements/name,elements/ancestors,total' }
     let(:get_path) do
       api_v3_paths.path_for :projects, select: select
     end
-
-    it 'is the reduced set of properties of the embedded elements' do
-      expected = {
+    let(:expected) do
+      {
+        total: 2,
         _embedded: {
           elements: [
+            {
+              id: parent_project.id,
+              name: parent_project.name,
+              _links: {
+                ancestors: []
+              }
+            },
             {
               id: project.id,
-              name: project.name
+              name: project.name,
+              _links: {
+                ancestors: [
+                  href: api_v3_paths.project(parent_project.id),
+                  title: parent_project.name
+                ]
+              }
             }
           ]
         }
       }
+    end
 
+    it 'is the reduced set of properties of the embedded elements' do
       expect(last_response.body)
         .to be_json_eql(expected.to_json)
     end