Prevent autogenerated OAuth username to clash with existing namespace.

app/models/namespace.rb

@@ -44,6 +44,10 @@ class Namespace < ActiveRecord::Base
 
   scope :root, -> { where('type IS NULL') }
 
+  def self.by_path(path)
+    where('lower(path) = :value', value: path.downcase).first
+  end
+
   def self.search(query)
     where("name LIKE :query OR path LIKE :query", query: "%#{query}%")
   end

app/models/user.rb

@@ -252,7 +252,7 @@ class User < ActiveRecord::Base
 
       counter = 0
       base = username
-      while by_login(username).present?
+      while User.by_login(username).present? || Namespace.by_path(username).present?
         counter += 1 
         username = "#{base}#{counter}"
       end
@@ -290,7 +290,8 @@ class User < ActiveRecord::Base
 
   def namespace_uniq
     namespace_name = self.username
-    if Namespace.find_by(path: namespace_name)
+    existing_namespace = Namespace.by_path(namespace_name)
+    if existing_namespace && existing_namespace != self.namespace
       self.errors.add :username, "already exists"
     end
   end

spec/models/user_spec.rb

@@ -303,8 +303,8 @@ describe User do
 
   describe ".clean_username" do
 
-    let!(:user1) { create(:user, username: "johngitlab-etc") }
-    let!(:user2) { create(:user, username: "JohnGitLab-etc1") }
+    let!(:user) { create(:user, username: "johngitlab-etc") }
+    let!(:namespace) { create(:namespace, path: "JohnGitLab-etc1") }
 
     it "cleans a username and makes sure it's available" do
       expect(User.clean_username("-john+gitlab-ETC%.git@gmail.com")).to eq("johngitlab-ETC2")