18 files changed, 369 insertions, 8 deletions

diff --git a/app/models/project.rb b/app/models/project.rb
index 2c4288c2b59..7f78eceec1e 100644
--- a/app/models/project.rb
+++ b/app/models/project.rb
@@ -160,6 +160,7 @@ class Project < ActiveRecord::Base
   has_one :pushover_service
   has_one :jira_service
   has_one :redmine_service
+  has_one :youtrack_service
   has_one :custom_issue_tracker_service
   has_one :bugzilla_service
   has_one :gitlab_issue_tracker_service, inverse_of: :project
diff --git a/app/models/project_services/youtrack_service.rb b/app/models/project_services/youtrack_service.rb
new file mode 100644
index 00000000000..957be685aea
--- /dev/null
+++ b/app/models/project_services/youtrack_service.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+class YoutrackService < IssueTrackerService
+  validates :project_url, :issues_url, presence: true, public_url: true, if: :activated?
+
+  prop_accessor :description, :project_url, :issues_url
+
+  # {PROJECT-KEY}-{NUMBER} Examples: YT-1, PRJ-1
+  def self.reference_pattern(only_long: false)
+    if only_long
+      /(?<issue>\b[A-Z][A-Za-z0-9_]*-\d+)/
+    else
+      /(?<issue>\b[A-Z][A-Za-z0-9_]*-\d+)|(#{Issue.reference_prefix}(?<issue>\d+))/
+    end
+  end
+
+  def title
+    'YouTrack'
+  end
+
+  def description
+    if self.properties && self.properties['description'].present?
+      self.properties['description']
+    else
+      'YouTrack issue tracker'
+    end
+  end
+
+  def self.to_param
+    'youtrack'
+  end
+
+  def fields
+    [
+      { type: 'text', name: 'description', placeholder: description },
+      { type: 'text', name: 'project_url', placeholder: 'Project url', required: true },
+      { type: 'text', name: 'issues_url', placeholder: 'Issue url', required: true }
+    ]
+  end
+end
diff --git a/app/models/service.rb b/app/models/service.rb
index 3461e0bfe70..da523bfa426 100644
--- a/app/models/service.rb
+++ b/app/models/service.rb
@@ -266,6 +266,7 @@ class Service < ActiveRecord::Base
       prometheus
       pushover
       redmine
+      youtrack
       slack_slash_commands
       slack
       teamcity
diff --git a/changelogs/unreleased/add-youtrack-integration.yml b/changelogs/unreleased/add-youtrack-integration.yml
new file mode 100644
index 00000000000..f500e625145
--- /dev/null
+++ b/changelogs/unreleased/add-youtrack-integration.yml
@@ -0,0 +1,5 @@
+---
+title: Add YouTrack integration service
+merge_request: 25361
+author: Yauhen Kotau @bessorion
+type: added
diff --git a/doc/api/services.md b/doc/api/services.md
index 9275a1ccda8..c44f5cc5781 100644
--- a/doc/api/services.md
+++ b/doc/api/services.md
@@ -1102,3 +1102,39 @@ GET /projects/:id/services/mock-ci
 ```
 
 [11435]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/11435
+
+## YouTrack
+
+YouTrack issue tracker
+
+### Create/Edit YouTrack service
+
+Set YouTrack service for a project.
+
+```
+PUT /projects/:id/services/youtrack
+```
+
+Parameters:
+
+| Parameter | Type | Required | Description |
+| --------- | ---- | -------- | ----------- |
+| `issues_url` | string | true | Issue url |
+| `project_url` | string | true | Project url |
+| `description` | string | false | Description |
+
+### Delete YouTrack Service
+
+Delete YouTrack service for a project.
+
+```
+DELETE /projects/:id/services/youtrack
+```
+
+### Get YouTrack Service Settings
+
+Get YouTrack service settings for a project.
+
+```
+GET /projects/:id/services/youtrack
+```
diff --git a/doc/integration/external-issue-tracker.md b/doc/integration/external-issue-tracker.md
index 075feaeead9..edd1af423ca 100644
--- a/doc/integration/external-issue-tracker.md
+++ b/doc/integration/external-issue-tracker.md
@@ -1,8 +1,8 @@
 # External issue tracker
 
 GitLab has a great issue tracker but you can also use an external one such as
-Jira, Redmine, or Bugzilla. Issue trackers are configurable per GitLab project and allow
-you to do the following:
+Jira, Redmine, YouTrack, or Bugzilla. Issue trackers are configurable per GitLab project
+and allow you to do the following:
 
 - you can reference these external issues inside GitLab interface
   (merge requests, commits, comments) and they will be automatically converted
@@ -20,6 +20,7 @@ To enable an external issue tracker you must configure the appropriate **Service
 Visit the links below for details:
 
 - [Redmine](../user/project/integrations/redmine.md)
+- [YouTrack](../user/project/integrations/youtrack.md)
 - [Jira](../user/project/integrations/jira.md)
 - [Bugzilla](../user/project/integrations/bugzilla.md)
 - [Custom Issue Tracker](../user/project/integrations/custom_issue_tracker.md)
diff --git a/doc/user/project/integrations/project_services.md b/doc/user/project/integrations/project_services.md
index cec9018b67f..e2f23827360 100644
--- a/doc/user/project/integrations/project_services.md
+++ b/doc/user/project/integrations/project_services.md
@@ -50,6 +50,7 @@ Click on the service links to see further configuration instructions and details
 | [Prometheus](prometheus.md) | Monitor the performance of your deployed apps |
 | Pushover | Pushover makes it easy to get real-time notifications on your Android device, iPhone, iPad, and Desktop |
 | [Redmine](redmine.md) | Redmine issue tracker |
+| [YouTrack](youtrack.md) | YouTrack issue tracker |
 
 ## Services templates
 
diff --git a/doc/user/project/integrations/youtrack.md b/doc/user/project/integrations/youtrack.md
new file mode 100644
index 00000000000..2ab14a8db2c
--- /dev/null
+++ b/doc/user/project/integrations/youtrack.md
@@ -0,0 +1,31 @@
+# YouTrack Service
+
+JetBrains YouTrack is a web-based issue tracking and project management platform.
+Please refer official [documentation](https://www.jetbrains.com/help/youtrack/standalone/YouTrack-Documentation.html) for details about YouTrack itself.
+
+
+1. To enable the YouTrack integration in a project, navigate to the
+[Integrations page](project_services.md#accessing-the-project-services), click
+the **YouTrack** service, and fill in the required details on the page as described
+in the table below.
+
+    | Field | Description |
+    | ----- | ----------- |
+    | `description`   | A name for the issue tracker (to differentiate between instances, for example) |
+    | `project_url`   | The URL to the project in YouTrack which is being linked to this GitLab project |
+    | `issues_url`    | The URL to the issue in YouTrack project that is linked to this GitLab project. Note that the `issues_url` requires `:id` in the URL. This ID is used by GitLab as a placeholder to replace the issue number. |
+
+    Once you have configured and enabled YouTrack you'll see the YouTrack link on the GitLab project pages that takes you to the appropriate YouTrack project.
+
+1. To disable the internal issue tracking system in a project, navigate to the General page, expand [Permissions](../settings/index.md#sharing-and-permissions), and slide the Issues switch invalid.
+
+    ![Issue configuration](img/issue_configuration.png)
+
+## Referencing issues in YouTrack
+
+Issues in YouTrack can be referenced as `<PROJECT>-<ID>` where `<PROJECT>`
+starts with a capital letter which is then followed by capital or lower case
+letters, numbers or underscores, and `<ID>` is a number (example `Api_32-143`).
+
+`<PROJECT>` part is included into issue_id and links can point any YouTrack
+project (`issues_url` + issue_id)
diff --git a/doc/user/project/issues/index.md b/doc/user/project/issues/index.md
index 5a3ac9c175b..907a305fe23 100644
--- a/doc/user/project/issues/index.md
+++ b/doc/user/project/issues/index.md
@@ -155,7 +155,7 @@ For further details, see [Importing issues from CSV](csv_import.md)
 
 Alternatively to GitLab's built-in Issue Tracker, you can also use an [external
 tracker](../../../integration/external-issue-tracker.md) such as Jira, Redmine,
-or Bugzilla.
+YouTrack, or Bugzilla.
 
 ### Issue API
 
diff --git a/lib/api/services.rb b/lib/api/services.rb
index 145897516a0..bda6be51553 100644
--- a/lib/api/services.rb
+++ b/lib/api/services.rb
@@ -592,6 +592,26 @@ module API
           desc: 'The description of the tracker'
         }
       ],
+      'youtrack' => [
+        {
+          required: true,
+          name: :project_url,
+          type: String,
+          desc: 'The project URL'
+        },
+        {
+          required: true,
+          name: :issues_url,
+          type: String,
+          desc: 'The issues URL'
+        },
+        {
+          required: false,
+          name: :description,
+          type: String,
+          desc: 'The description of the tracker'
+        }
+      ],
       'slack' => [
         CHAT_NOTIFICATION_SETTINGS,
         CHAT_NOTIFICATION_FLAGS,
@@ -665,6 +685,7 @@ module API
       PrometheusService,
       PushoverService,
       RedmineService,
+      YoutrackService,
       SlackService,
       MattermostService,
       MicrosoftTeamsService,
diff --git a/spec/factories/projects.rb b/spec/factories/projects.rb
index f7ef34d773b..30d3b22d868 100644
--- a/spec/factories/projects.rb
+++ b/spec/factories/projects.rb
@@ -313,6 +313,20 @@ FactoryBot.define do
     end
   end
 
+  factory :youtrack_project, parent: :project do
+    has_external_issue_tracker true
+
+    after :create do |project|
+      project.create_youtrack_service(
+        active: true,
+        properties: {
+          'project_url' => 'http://youtrack/projects/project_guid_in_youtrack',
+          'issues_url' => 'http://youtrack/issues/:id'
+        }
+      )
+    end
+  end
+
   factory :jira_project, parent: :project do
     has_external_issue_tracker true
     jira_service
diff --git a/spec/features/projects/services/user_activates_issue_tracker_spec.rb b/spec/features/projects/services/user_activates_issue_tracker_spec.rb
index 7cd5b12802b..74b9a2b20cd 100644
--- a/spec/features/projects/services/user_activates_issue_tracker_spec.rb
+++ b/spec/features/projects/services/user_activates_issue_tracker_spec.rb
@@ -6,11 +6,17 @@ describe 'User activates issue tracker', :js do
 
   let(:url) { 'http://tracker.example.com' }
 
-  def fill_form(active = true)
+  def fill_short_form(active = true)
     check 'Active' if active
 
     fill_in 'service_project_url', with: url
     fill_in 'service_issues_url', with: "#{url}/:id"
+  end
+
+  def fill_full_form(active = true)
+    fill_short_form(active)
+    check 'Active' if active
+
     fill_in 'service_new_issue_url', with: url
   end
 
@@ -21,14 +27,20 @@ describe 'User activates issue tracker', :js do
     visit project_settings_integrations_path(project)
   end
 
-  shared_examples 'external issue tracker activation' do |tracker:|
+  shared_examples 'external issue tracker activation' do |tracker:, skip_new_issue_url: false|
     describe 'user sets and activates the Service' do
       context 'when the connection test succeeds' do
         before do
           stub_request(:head, url).to_return(headers: { 'Content-Type' => 'application/json' })
 
           click_link(tracker)
-          fill_form
+
+          if skip_new_issue_url
+            fill_short_form
+          else
+            fill_full_form
+          end
+
           click_button('Test settings and save changes')
           wait_for_requests
         end
@@ -50,7 +62,13 @@ describe 'User activates issue tracker', :js do
           stub_request(:head, url).to_raise(HTTParty::Error)
 
           click_link(tracker)
-          fill_form
+
+          if skip_new_issue_url
+            fill_short_form
+          else
+            fill_full_form
+          end
+
           click_button('Test settings and save changes')
           wait_for_requests
 
@@ -69,7 +87,13 @@ describe 'User activates issue tracker', :js do
     describe 'user sets the service but keeps it disabled' do
       before do
         click_link(tracker)
-        fill_form(false)
+
+        if skip_new_issue_url
+          fill_short_form(false)
+        else
+          fill_full_form(false)
+        end
+
         click_button('Save changes')
       end
 
@@ -87,6 +111,7 @@ describe 'User activates issue tracker', :js do
   end
 
   it_behaves_like 'external issue tracker activation', tracker: 'Redmine'
+  it_behaves_like 'external issue tracker activation', tracker: 'YouTrack', skip_new_issue_url: true
   it_behaves_like 'external issue tracker activation', tracker: 'Bugzilla'
   it_behaves_like 'external issue tracker activation', tracker: 'Custom Issue Tracker'
 end
diff --git a/spec/features/projects/services/user_activates_youtrack_spec.rb b/spec/features/projects/services/user_activates_youtrack_spec.rb
new file mode 100644
index 00000000000..bb6a030c1cf
--- /dev/null
+++ b/spec/features/projects/services/user_activates_youtrack_spec.rb
@@ -0,0 +1,89 @@
+require 'spec_helper'
+
+describe 'User activates issue tracker', :js do
+  let(:user) { create(:user) }
+  let(:project) { create(:project) }
+
+  let(:url) { 'http://tracker.example.com' }
+
+  def fill_form(active = true)
+    check 'Active' if active
+
+    fill_in 'service_project_url', with: url
+    fill_in 'service_issues_url', with: "#{url}/:id"
+  end
+
+  before do
+    project.add_maintainer(user)
+    sign_in(user)
+
+    visit project_settings_integrations_path(project)
+  end
+
+  shared_examples 'external issue tracker activation' do |tracker:|
+    describe 'user sets and activates the Service' do
+      context 'when the connection test succeeds' do
+        before do
+          stub_request(:head, url).to_return(headers: { 'Content-Type' => 'application/json' })
+
+          click_link(tracker)
+          fill_form
+          click_button('Test settings and save changes')
+          wait_for_requests
+        end
+
+        it 'activates the service' do
+          expect(page).to have_content("#{tracker} activated.")
+          expect(current_path).to eq(project_settings_integrations_path(project))
+        end
+
+        it 'shows the link in the menu' do
+          page.within('.nav-sidebar') do
+            expect(page).to have_link(tracker, href: url)
+          end
+        end
+      end
+
+      context 'when the connection test fails' do
+        it 'activates the service' do
+          stub_request(:head, url).to_raise(HTTParty::Error)
+
+          click_link(tracker)
+          fill_form
+          click_button('Test settings and save changes')
+          wait_for_requests
+
+          expect(find('.flash-container-page')).to have_content 'Test failed.'
+          expect(find('.flash-container-page')).to have_content 'Save anyway'
+
+          find('.flash-alert .flash-action').click
+          wait_for_requests
+
+          expect(page).to have_content("#{tracker} activated.")
+          expect(current_path).to eq(project_settings_integrations_path(project))
+        end
+      end
+    end
+
+    describe 'user sets the service but keeps it disabled' do
+      before do
+        click_link(tracker)
+        fill_form(false)
+        click_button('Save changes')
+      end
+
+      it 'saves but does not activate the service' do
+        expect(page).to have_content("#{tracker} settings saved, but not activated.")
+        expect(current_path).to eq(project_settings_integrations_path(project))
+      end
+
+      it 'does not show the external tracker link in the menu' do
+        page.within('.nav-sidebar') do
+          expect(page).not_to have_link(tracker, href: url)
+        end
+      end
+    end
+  end
+
+  it_behaves_like 'external issue tracker activation', tracker: 'YouTrack'
+end
diff --git a/spec/lib/banzai/filter/external_issue_reference_filter_spec.rb b/spec/lib/banzai/filter/external_issue_reference_filter_spec.rb
index a0270d93d50..43222ddb5e2 100644
--- a/spec/lib/banzai/filter/external_issue_reference_filter_spec.rb
+++ b/spec/lib/banzai/filter/external_issue_reference_filter_spec.rb
@@ -121,6 +121,42 @@ describe Banzai::Filter::ExternalIssueReferenceFilter do
     end
   end
 
+  context "youtrack project" do
+    let(:project) { create(:youtrack_project) }
+
+    before do
+      project.update!(issues_enabled: false)
+    end
+
+    context "with right markdown" do
+      let(:issue) { ExternalIssue.new("YT-123", project) }
+      let(:reference) { issue.to_reference }
+
+      it_behaves_like "external issue tracker"
+    end
+
+    context "with underscores in the prefix" do
+      let(:issue) { ExternalIssue.new("PRJ_1-123", project) }
+      let(:reference) { issue.to_reference }
+
+      it_behaves_like "external issue tracker"
+    end
+
+    context "with lowercase letters in the prefix" do
+      let(:issue) { ExternalIssue.new("YTkPrj-123", project) }
+      let(:reference) { issue.to_reference }
+
+      it_behaves_like "external issue tracker"
+    end
+
+    context "with a single-letter prefix" do
+      let(:issue) { ExternalIssue.new("T-123", project) }
+      let(:reference) { issue.to_reference }
+
+      it_behaves_like "external issue tracker"
+    end
+  end
+
   context "jira project" do
     let(:project) { create(:jira_project) }
     let(:reference) { issue.to_reference }
diff --git a/spec/lib/gitlab/import_export/all_models.yml b/spec/lib/gitlab/import_export/all_models.yml
index f2eccec4635..018a5d3dd3d 100644
--- a/spec/lib/gitlab/import_export/all_models.yml
+++ b/spec/lib/gitlab/import_export/all_models.yml
@@ -233,6 +233,7 @@ project:
 - pushover_service
 - jira_service
 - redmine_service
+- youtrack_service
 - custom_issue_tracker_service
 - bugzilla_service
 - gitlab_issue_tracker_service
diff --git a/spec/lib/gitlab/import_export/project.json b/spec/lib/gitlab/import_export/project.json
index 1327f414498..773651dd226 100644
--- a/spec/lib/gitlab/import_export/project.json
+++ b/spec/lib/gitlab/import_export/project.json
@@ -6630,6 +6630,26 @@
   "deploy_keys": [],
   "services": [
     {
+      "id": 101,
+      "title": "YouTrack",
+      "project_id": 5,
+      "created_at": "2016-06-14T15:01:51.327Z",
+      "updated_at": "2016-06-14T15:01:51.327Z",
+      "active": false,
+      "properties": {},
+      "template": false,
+      "push_events": true,
+      "issues_events": true,
+      "merge_requests_events": true,
+      "tag_push_events": true,
+      "note_events": true,
+      "job_events": true,
+      "type": "YoutrackService",
+      "category": "issue_tracker",
+      "default": false,
+      "wiki_page_events": true
+    },
+    {
       "id": 100,
       "title": "JetBrains TeamCity CI",
       "project_id": 5,
diff --git a/spec/models/project_services/youtrack_service_spec.rb b/spec/models/project_services/youtrack_service_spec.rb
new file mode 100644
index 00000000000..9524b526a46
--- /dev/null
+++ b/spec/models/project_services/youtrack_service_spec.rb
@@ -0,0 +1,38 @@
+require 'spec_helper'
+
+describe YoutrackService do
+  describe 'Associations' do
+    it { is_expected.to belong_to :project }
+    it { is_expected.to have_one :service_hook }
+  end
+
+  describe 'Validations' do
+    context 'when service is active' do
+      before do
+        subject.active = true
+      end
+
+      it { is_expected.to validate_presence_of(:project_url) }
+      it { is_expected.to validate_presence_of(:issues_url) }
+      it_behaves_like 'issue tracker service URL attribute', :project_url
+      it_behaves_like 'issue tracker service URL attribute', :issues_url
+    end
+
+    context 'when service is inactive' do
+      before do
+        subject.active = false
+      end
+
+      it { is_expected.not_to validate_presence_of(:project_url) }
+      it { is_expected.not_to validate_presence_of(:issues_url) }
+    end
+  end
+
+  describe '.reference_pattern' do
+    it_behaves_like 'allows project key on reference pattern'
+
+    it 'does allow project prefix on the reference' do
+      expect(described_class.reference_pattern.match('YT-123')[:issue]).to eq('YT-123')
+    end
+  end
+end
diff --git a/spec/models/project_spec.rb b/spec/models/project_spec.rb
index 65cf04de13c..9cc9894003d 100644
--- a/spec/models/project_spec.rb
+++ b/spec/models/project_spec.rb
@@ -50,6 +50,7 @@ describe Project do
     it { is_expected.to have_one(:teamcity_service) }
     it { is_expected.to have_one(:jira_service) }
     it { is_expected.to have_one(:redmine_service) }
+    it { is_expected.to have_one(:youtrack_service) }
     it { is_expected.to have_one(:custom_issue_tracker_service) }
     it { is_expected.to have_one(:bugzilla_service) }
     it { is_expected.to have_one(:gitlab_issue_tracker_service) }