Merge branch 'feature/group-level-labels' into 'master'

Add group level labels

## What does this MR do?

Add group level labels.

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

* `LabelsFinder`
* `Gitlab::Gfm::ReferenceRewriter`
* `Banzai::Filter::LabelReferenceFilter`

## Why was this MR needed?

We'll be adding more feature that allow you to do cross-project management of issues.

## Screenshots (if relevant)

* Group Labels
    ![Group Labels](/uploads/2244c06ad68eae4fb246fb4c81bf8060/2.png)

* Project Labels
    ![Project Labels](/uploads/c5839516d2282b51f7418d9dadbeceb4/1.png)

* Expanded references for group labels when moving issue to another project
    ![Expanded references for group labels when moving issue to another project](/uploads/0c9ab248a8420d4978d59349ae3d42e5/3.png)

## 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)
- [x] API support added
- Tests
  - [x] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [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)

## What are the relevant issue numbers?

#19997

See merge request !6425

6 files changed, 254 insertions, 56 deletions

diff --git a/spec/models/group_label_spec.rb b/spec/models/group_label_spec.rb
new file mode 100644
index 00000000000..85eb889225b
--- /dev/null
+++ b/spec/models/group_label_spec.rb
@@ -0,0 +1,47 @@
+require 'spec_helper'
+
+describe GroupLabel, models: true do
+  describe 'relationships' do
+    it { is_expected.to belong_to(:group) }
+  end
+
+  describe 'validations' do
+    it { is_expected.to validate_presence_of(:group) }
+  end
+
+  describe '#subject' do
+    it 'aliases group to subject' do
+      subject = described_class.new(group: build(:group))
+
+      expect(subject.subject).to be(subject.group)
+    end
+  end
+
+  describe '#to_reference' do
+    let(:label) { create(:group_label) }
+
+    context 'using id' do
+      it 'returns a String reference to the object' do
+        expect(label.to_reference).to eq "~#{label.id}"
+      end
+    end
+
+    context 'using name' do
+      it 'returns a String reference to the object' do
+        expect(label.to_reference(format: :name)).to eq %(~"#{label.name}")
+      end
+
+      it 'uses id when name contains double quote' do
+        label = create(:label, name: %q{"irony"})
+        expect(label.to_reference(format: :name)).to eq "~#{label.id}"
+      end
+    end
+
+    context 'using invalid format' do
+      it 'raises error' do
+        expect { label.to_reference(format: :invalid) }
+          .to raise_error StandardError, /Unknown format/
+      end
+    end
+  end
+end
diff --git a/spec/models/group_spec.rb b/spec/models/group_spec.rb
index 0b3ef9b98fd..ac862055ebc 100644
--- a/spec/models/group_spec.rb
+++ b/spec/models/group_spec.rb
@@ -12,6 +12,7 @@ describe Group, models: true do
     it { is_expected.to have_many(:project_group_links).dependent(:destroy) }
     it { is_expected.to have_many(:shared_projects).through(:project_group_links) }
     it { is_expected.to have_many(:notification_settings).dependent(:destroy) }
+    it { is_expected.to have_many(:labels).class_name('GroupLabel') }
 
     describe '#members & #requesters' do
       let(:requester) { create(:user) }
diff --git a/spec/models/label_priority_spec.rb b/spec/models/label_priority_spec.rb
new file mode 100644
index 00000000000..d18c2f7949a
--- /dev/null
+++ b/spec/models/label_priority_spec.rb
@@ -0,0 +1,20 @@
+require 'spec_helper'
+
+describe LabelPriority, models: true do
+  describe 'relationships' do
+    it { is_expected.to belong_to(:project) }
+    it { is_expected.to belong_to(:label) }
+  end
+
+  describe 'validations' do
+    it { is_expected.to validate_presence_of(:project) }
+    it { is_expected.to validate_presence_of(:label) }
+    it { is_expected.to validate_numericality_of(:priority).only_integer.is_greater_than_or_equal_to(0) }
+
+    it 'validates uniqueness of label_id scoped to project_id' do
+      create(:label_priority)
+
+      expect(subject).to validate_uniqueness_of(:label_id).scoped_to(:project_id)
+    end
+  end
+end
diff --git a/spec/models/label_spec.rb b/spec/models/label_spec.rb
index 5a5d1a5d60c..0c163659a71 100644
--- a/spec/models/label_spec.rb
+++ b/spec/models/label_spec.rb
@@ -1,46 +1,42 @@
 require 'spec_helper'
 
 describe Label, models: true do
-  let(:label) { create(:label) }
+  describe 'modules' do
+    it { is_expected.to include_module(Referable) }
+    it { is_expected.to include_module(Subscribable) }
+  end
 
   describe 'associations' do
-    it { is_expected.to belong_to(:project) }
-
-    it { is_expected.to have_many(:label_links).dependent(:destroy) }
     it { is_expected.to have_many(:issues).through(:label_links).source(:target) }
+    it { is_expected.to have_many(:label_links).dependent(:destroy) }
     it { is_expected.to have_many(:lists).dependent(:destroy) }
-  end
-
-  describe 'modules' do
-    subject { described_class }
-
-    it { is_expected.to include_module(Referable) }
+    it { is_expected.to have_many(:priorities).class_name('LabelPriority') }
   end
 
   describe 'validation' do
-    it { is_expected.to validate_presence_of(:project) }
+    it { is_expected.to validate_uniqueness_of(:title).scoped_to([:group_id, :project_id]) }
 
     it 'validates color code' do
-      expect(label).not_to allow_value('G-ITLAB').for(:color)
-      expect(label).not_to allow_value('AABBCC').for(:color)
-      expect(label).not_to allow_value('#AABBCCEE').for(:color)
-      expect(label).not_to allow_value('GGHHII').for(:color)
-      expect(label).not_to allow_value('#').for(:color)
-      expect(label).not_to allow_value('').for(:color)
-
-      expect(label).to allow_value('#AABBCC').for(:color)
-      expect(label).to allow_value('#abcdef').for(:color)
+      is_expected.not_to allow_value('G-ITLAB').for(:color)
+      is_expected.not_to allow_value('AABBCC').for(:color)
+      is_expected.not_to allow_value('#AABBCCEE').for(:color)
+      is_expected.not_to allow_value('GGHHII').for(:color)
+      is_expected.not_to allow_value('#').for(:color)
+      is_expected.not_to allow_value('').for(:color)
+
+      is_expected.to allow_value('#AABBCC').for(:color)
+      is_expected.to allow_value('#abcdef').for(:color)
     end
 
     it 'validates title' do
-      expect(label).not_to allow_value('G,ITLAB').for(:title)
-      expect(label).not_to allow_value('').for(:title)
-
-      expect(label).to allow_value('GITLAB').for(:title)
-      expect(label).to allow_value('gitlab').for(:title)
-      expect(label).to allow_value('G?ITLAB').for(:title)
-      expect(label).to allow_value('G&ITLAB').for(:title)
-      expect(label).to allow_value("customer's request").for(:title)
+      is_expected.not_to allow_value('G,ITLAB').for(:title)
+      is_expected.not_to allow_value('').for(:title)
+
+      is_expected.to allow_value('GITLAB').for(:title)
+      is_expected.to allow_value('gitlab').for(:title)
+      is_expected.to allow_value('G?ITLAB').for(:title)
+      is_expected.to allow_value('G&ITLAB').for(:title)
+      is_expected.to allow_value("customer's request").for(:title)
     end
   end
 
@@ -51,45 +47,59 @@ describe Label, models: true do
     end
   end
 
-  describe '#to_reference' do
-    context 'using id' do
-      it 'returns a String reference to the object' do
-        expect(label.to_reference).to eq "~#{label.id}"
-      end
-    end
+  describe 'priorization' do
+    subject(:label) { create(:label) }
 
-    context 'using name' do
-      it 'returns a String reference to the object' do
-        expect(label.to_reference(format: :name)).to eq %(~"#{label.name}")
+    let(:project) { label.project }
+
+    describe '#prioritize!' do
+      context 'when label is not prioritized' do
+        it 'creates a label priority' do
+          expect { label.prioritize!(project, 1) }.to change(label.priorities, :count).by(1)
+        end
+
+        it 'sets label priority' do
+          label.prioritize!(project, 1)
+
+          expect(label.priorities.first.priority).to eq 1
+        end
       end
 
-      it 'uses id when name contains double quote' do
-        label = create(:label, name: %q{"irony"})
-        expect(label.to_reference(format: :name)).to eq "~#{label.id}"
+      context 'when label is prioritized' do
+        let!(:priority) { create(:label_priority, project: project, label: label, priority: 0) }
+
+        it 'does not create a label priority' do
+          expect { label.prioritize!(project, 1) }.not_to change(label.priorities, :count)
+        end
+
+        it 'updates label priority' do
+          label.prioritize!(project, 1)
+
+          expect(priority.reload.priority).to eq 1
+        end
       end
     end
 
-    context 'using invalid format' do
-      it 'raises error' do
-        expect { label.to_reference(format: :invalid) }
-          .to raise_error StandardError, /Unknown format/
+    describe '#unprioritize!' do
+      it 'removes label priority' do
+        create(:label_priority, project: project, label: label, priority: 0)
+
+        expect { label.unprioritize!(project) }.to change(label.priorities, :count).by(-1)
       end
     end
 
-    context 'cross project reference' do
-      let(:project) { create(:project) }
-
-      context 'using name' do
-        it 'returns cross reference with label name' do
-          expect(label.to_reference(project, format: :name))
-            .to eq %Q(#{label.project.to_reference}~"#{label.name}")
+    describe '#priority' do
+      context 'when label is not prioritized' do
+        it 'returns nil' do
+          expect(label.priority(project)).to be_nil
         end
       end
 
-      context 'using id' do
-        it 'returns cross reference with label id' do
-          expect(label.to_reference(project, format: :id))
-            .to eq %Q(#{label.project.to_reference}~#{label.id})
+      context 'when label is prioritized' do
+        it 'returns label priority' do
+          create(:label_priority, project: project, label: label, priority: 1)
+
+          expect(label.priority(project)).to eq 1
         end
       end
     end
diff --git a/spec/models/project_label_spec.rb b/spec/models/project_label_spec.rb
new file mode 100644
index 00000000000..18c9d449ee5
--- /dev/null
+++ b/spec/models/project_label_spec.rb
@@ -0,0 +1,120 @@
+require 'spec_helper'
+
+describe ProjectLabel, models: true do
+  describe 'relationships' do
+    it { is_expected.to belong_to(:project) }
+  end
+
+  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
+
+      it 'does not returns error when title does not change' do
+        project_label = create(:label, project: project, name: 'Security')
+        create(:group_label, group: group, name: 'Security')
+        project_label.description = 'Security related stuff.'
+
+        project_label.valid?
+
+        expect(project_label.errors[:title]).to be_empty
+      end
+    end
+
+    context 'when attempting to add more than one priority to the project label' do
+      it 'returns error' do
+        subject.priorities.build
+        subject.priorities.build
+
+        subject.valid?
+
+        expect(subject.errors[:priorities]).to include 'Number of permitted priorities exceeded'
+      end
+    end
+  end
+
+  describe '#subject' do
+    it 'aliases project to subject' do
+      subject = described_class.new(project: build(:empty_project))
+
+      expect(subject.subject).to be(subject.project)
+    end
+  end
+
+  describe '#to_reference' do
+    let(:label) { create(:label) }
+
+    context 'using id' do
+      it 'returns a String reference to the object' do
+        expect(label.to_reference).to eq "~#{label.id}"
+      end
+    end
+
+    context 'using name' do
+      it 'returns a String reference to the object' do
+        expect(label.to_reference(format: :name)).to eq %(~"#{label.name}")
+      end
+
+      it 'uses id when name contains double quote' do
+        label = create(:label, name: %q{"irony"})
+        expect(label.to_reference(format: :name)).to eq "~#{label.id}"
+      end
+    end
+
+    context 'using invalid format' do
+      it 'raises error' do
+        expect { label.to_reference(format: :invalid) }
+          .to raise_error StandardError, /Unknown format/
+      end
+    end
+
+    context 'cross project reference' do
+      let(:project) { create(:project) }
+
+      context 'using name' do
+        it 'returns cross reference with label name' do
+          expect(label.to_reference(project, format: :name))
+            .to eq %Q(#{label.project.to_reference}~"#{label.name}")
+        end
+      end
+
+      context 'using id' do
+        it 'returns cross reference with label id' do
+          expect(label.to_reference(project, format: :id))
+            .to eq %Q(#{label.project.to_reference}~#{label.id})
+        end
+      end
+    end
+  end
+end
diff --git a/spec/models/project_spec.rb b/spec/models/project_spec.rb
index 67dbcc362f6..e6d98e25d0b 100644
--- a/spec/models/project_spec.rb
+++ b/spec/models/project_spec.rb
@@ -56,7 +56,7 @@ describe Project, models: true do
     it { is_expected.to have_many(:runners) }
     it { is_expected.to have_many(:variables) }
     it { is_expected.to have_many(:triggers) }
-    it { is_expected.to have_many(:labels).dependent(:destroy) }
+    it { is_expected.to have_many(:labels).class_name('ProjectLabel').dependent(:destroy) }
     it { is_expected.to have_many(:users_star_projects).dependent(:destroy) }
     it { is_expected.to have_many(:environments).dependent(:destroy) }
     it { is_expected.to have_many(:deployments).dependent(:destroy) }