Fix endless redirections when accessing user OAuth applications when they are disabled

Also hides the "Applications" nav button if OAuth applications are disabled by the admin.

Closes #14770

CHANGELOG

@@ -3,6 +3,7 @@ Please view this file on the master branch, on stable branches it's out of date.
 v 8.9.0 (unreleased)
   - Bulk assign/unassign labels to issues.
   - Ability to prioritize labels !4009 / !3205 (Thijs Wouters)
+  - Fix endless redirections when accessing user OAuth applications when they are disabled
   - Allow enabling wiki page events from Webhook management UI
   - Bump rouge to 1.11.0
   - Make EmailsOnPushWorker use Sidekiq mailers queue

app/controllers/oauth/applications_controller.rb

@@ -32,7 +32,7 @@ class Oauth::ApplicationsController < Doorkeeper::ApplicationsController
   def verify_user_oauth_applications_enabled
     return if current_application_settings.user_oauth_applications?
 
-    redirect_to applications_profile_url
+    redirect_to profile_path
   end
 
   def set_index_vars

app/views/layouts/nav/_profile.html.haml

@@ -10,11 +10,12 @@
       = icon('gear fw')
       %span
         Account
-  = nav_link(controller: 'oauth/applications') do
-    = link_to applications_profile_path, title: 'Applications' do
-      = icon('cloud fw')
-      %span
-        Applications
+  - if current_application_settings.user_oauth_applications?
+    = nav_link(controller: 'oauth/applications') do
+      = link_to applications_profile_path, title: 'Applications' do
+        = icon('cloud fw')
+        %span
+          Applications
   = nav_link(controller: :emails) do
     = link_to profile_emails_path, title: 'Emails' do
       = icon('envelope-o fw')

spec/controllers/oauth/applications_controller_spec.rb

+require 'spec_helper'
+
+describe Oauth::ApplicationsController do
+  let(:user) { create(:user) }
+
+  context 'project members' do
+    before do
+      sign_in(user)
+    end
+
+    describe 'GET #index' do
+      it 'shows list of applications' do
+        get :index
+
+        expect(response.status).to eq(200)
+      end
+
+      it 'redirects back to profile page if OAuth applications are disabled' do
+        settings = double(user_oauth_applications?: false)
+        allow_any_instance_of(Gitlab::CurrentSettings).to receive(:current_application_settings).and_return(settings)
+
+        get :index
+
+        expect(response.status).to eq(302)
+        expect(response).to redirect_to(profile_path)
+      end
+    end
+  end
+end