Validate if project label title does not exist at group level

app/models/label.rb

@@ -24,13 +24,14 @@ class Label < ActiveRecord::Base
 
   # Don't allow ',' for label titles
   validates :title, presence: true, format: { with: /\A[^,]+\z/ }
-  validates :title, uniqueness: true, unless: :template?
+  validates :title, uniqueness: { scope: [:group_id, :project_id] }
 
   before_save :nullify_priority
 
   default_scope { order(title: :asc) }
 
   scope :templates, -> { where(template: true) }
+  scope :with_title, ->(title) { where(title: title) }
 
   def self.prioritized
     where.not(priority: nil).reorder(:priority, :title)

app/models/project_label.rb

@@ -2,4 +2,18 @@ class ProjectLabel < Label
   belongs_to :project
 
   validates :project, presence: true
+
+  validate :title_must_not_exist_at_group_level
+
+  delegate :group, to: :project, allow_nil: true
+
+  private
+
+  def title_must_not_exist_at_group_level
+    return unless group.present?
+
+    if group.labels.with_title(self.title).exists?
+      errors.add(:title, :label_already_exists_at_group_level, group: group.name)
+    end
+  end
 end

config/locales/en.yml

@@ -5,6 +5,7 @@ en:
   hello: "Hello world"
   errors:
     messages:
+      label_already_exists_at_group_level: "already exists at group level for %{group}. Please choose another one."
       wrong_size: "is the wrong size (should be %{file_size})"
       size_too_small: "is too small (should be at least %{file_size})"
       size_too_big: "is too big (should be at most %{file_size})"

spec/factories/labels.rb

@@ -4,4 +4,10 @@ FactoryGirl.define do
     color "#990000"
     project
   end
+
+  factory :group_label, class: GroupLabel do
+    sequence(:title) { |n| "label#{n}" }
+    color "#990000"
+    group
+  end
 end

spec/models/label_spec.rb

@@ -13,7 +13,7 @@ describe Label, models: true do
   end
 
   describe 'validation' do
-    it { is_expected.to validate_uniqueness_of(:title) }
+    it { is_expected.to validate_uniqueness_of(:title).scoped_to([:group_id, :project_id]) }
 
     it 'validates color code' do
       is_expected.not_to allow_value('G-ITLAB').for(:color)

spec/models/project_label_spec.rb

@@ -7,5 +7,39 @@ describe ProjectLabel, models: true do
 
   describe 'validations' do
     it { is_expected.to validate_presence_of(:project) }
+
+    context 'validates if title must not exist at group level' do
+      let(:group) { create(:group, name: 'gitlab-org') }
+      let(:project) { create(:empty_project, group: group) }
+
+      before do
+        create(:group_label, group: group, title: 'Bug')
+      end
+
+      it 'returns error if title already exists at group level' do
+        label = described_class.new(project: project, title: 'Bug')
+
+        label.valid?
+
+        expect(label.errors[:title]).to include 'already exists at group level for gitlab-org. Please choose another one.'
+      end
+
+      it 'does not returns error if title does not exist at group level' do
+        label = described_class.new(project: project, title: 'Security')
+
+        label.valid?
+
+        expect(label.errors[:title]).to be_empty
+      end
+
+      it 'does not returns error if project does not belong to group' do
+        another_project = create(:empty_project)
+        label = described_class.new(project: another_project, title: 'Bug')
+
+        label.valid?
+
+        expect(label.errors[:title]).to be_empty
+      end
+    end
   end
 end