Merge branch '21446-service-external-wiki-only-works-when-project-wiki-is-enabled' into 'master'

Fix "Wiki" link not appearing in navigation for projects with external wiki

## Are there points in the code the reviewer needs to double check?

No

## What are the relevant issue numbers?

Closes #21446

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [x] Added for this feature/bug
  - [ ] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !6057

CHANGELOG

@@ -51,6 +51,7 @@ v 8.11.3 (unreleased)
   - Allow system info page to handle case where info is unavailable
   - Label list shows all issues (opened or closed) with that label
   - Don't show resolve conflicts link before MR status is updated
+  - Fix "Wiki" link not appearing in navigation for projects with external wiki
   - Fix IE11 fork button bug !598
   - Don't prevent viewing the MR when git refs for conflicts can't be found on disk
   - Fix external issue tracker "Issues" link leading to 404s

app/models/ability.rb

@@ -355,7 +355,7 @@ class Ability
         rules += named_abilities('project_snippet')
       end
 
-      unless project.wiki_enabled
+      unless project.has_wiki?
         rules += named_abilities('wiki')
       end
 

app/models/project.rb

@@ -680,6 +680,10 @@ class Project < ActiveRecord::Base
     update_column(:has_external_issue_tracker, services.external_issue_trackers.any?)
   end
 
+  def has_wiki?
+    wiki_enabled? || has_external_wiki?
+  end
+
   def external_wiki
     if has_external_wiki.nil?
       cache_has_external_wiki # Populate

spec/models/ability_spec.rb

@@ -282,4 +282,17 @@ describe Ability, lib: true do
       end
     end
   end
+
+  describe '.project_disabled_features_rules' do
+    let(:project) { build(:project) }
+
+    subject { described_class.project_disabled_features_rules(project) }
+
+    context 'wiki named abilities' do
+      it 'disables wiki abilities if the project has no wiki' do
+        expect(project).to receive(:has_wiki?).and_return(false)
+        expect(subject).to include(:read_wiki, :create_wiki, :update_wiki, :admin_wiki)
+      end
+    end
+  end
 end

spec/models/project_spec.rb

@@ -506,6 +506,18 @@ describe Project, models: true do
     end
   end
 
+  describe '#has_wiki?' do
+    let(:no_wiki_project) { build(:project, wiki_enabled: false, has_external_wiki: false) }
+    let(:wiki_enabled_project) { build(:project, wiki_enabled: true) }
+    let(:external_wiki_project) { build(:project, has_external_wiki: true) }
+
+    it 'returns true if project is wiki enabled or has external wiki' do
+      expect(wiki_enabled_project).to have_wiki
+      expect(external_wiki_project).to have_wiki
+      expect(no_wiki_project).not_to have_wiki
+    end
+  end
+
   describe '#external_wiki' do
     let(:project) { create(:project) }