Original implementation to allow users to subscribe to labels

1. Allow subscribing (the current user) to a label

- Refactor the `Subscription` coffeescript class
  - The main change is that it accepts a container, and conducts all
    DOM queries within its scope. We need this because the labels
    page has multiple instances of `Subscription` on the same page.

2. Creating an issue or MR with labels notifies users subscribed to those labels

- Label `has_many` subscribers through subscriptions.

3. Adding a label to an issue or MR notifies users subscribed to those labels

- This only applies to subscribers of the label that has just been
  added, not all labels for the issue.

7 files changed, 216 insertions, 15 deletions

diff --git a/spec/factories/labels.rb b/spec/factories/labels.rb
index 6e70af10af3..91a7400afa1 100644
--- a/spec/factories/labels.rb
+++ b/spec/factories/labels.rb
@@ -13,7 +13,7 @@
 
 FactoryGirl.define do
   factory :label do
-    title "Bug"
+    title { FFaker::Color.name }
     color "#990000"
     project
   end
diff --git a/spec/models/concerns/subscribable_spec.rb b/spec/models/concerns/subscribable_spec.rb
new file mode 100644
index 00000000000..9ee60426a5d
--- /dev/null
+++ b/spec/models/concerns/subscribable_spec.rb
@@ -0,0 +1,16 @@
+require "spec_helper"
+
+describe Subscribable, "Subscribable" do
+  let(:resource) { create(:issue) }
+  let(:user) { create(:user) }
+
+  describe "#subscribed?" do
+    it do
+      expect(resource.subscribed?(user)).to be_falsey
+      resource.toggle_subscription(user)
+      expect(resource.subscribed?(user)).to be_truthy
+      resource.toggle_subscription(user)
+      expect(resource.subscribed?(user)).to be_falsey
+    end
+  end
+end
diff --git a/spec/services/issues/update_service_spec.rb b/spec/services/issues/update_service_spec.rb
index e579e49dfa7..dc9d8329751 100644
--- a/spec/services/issues/update_service_spec.rb
+++ b/spec/services/issues/update_service_spec.rb
@@ -48,7 +48,7 @@ describe Issues::UpdateService, services: true do
       it { expect(@issue.assignee).to eq(user2) }
       it { expect(@issue).to be_closed }
       it { expect(@issue.labels.count).to eq(1) }
-      it { expect(@issue.labels.first.title).to eq('Bug') }
+      it { expect(@issue.labels.first.title).to eq(label.name) }
 
       it 'should send email to user2 about assign of new issue and email to user3 about issue unassignment' do
         deliveries = ActionMailer::Base.deliveries
@@ -148,6 +148,60 @@ describe Issues::UpdateService, services: true do
       end
     end
 
+    context "when the issue is relabeled" do
+      it "sends notifications for subscribers of newly added labels" do
+        subscriber, non_subscriber = create_list(:user, 2)
+        label.toggle_subscription(subscriber)
+        2.times { label.toggle_subscription(non_subscriber) }
+
+        opts = { label_ids: [label.id] }
+
+        perform_enqueued_jobs do
+          @issue = Issues::UpdateService.new(project, user, opts).execute(issue)
+        end
+
+        @issue.reload
+        should_email(subscriber)
+        should_not_email(non_subscriber)
+      end
+
+      it "does send notifications for existing labels" do
+        second_label = create(:label)
+        issue.labels << label
+        subscriber, non_subscriber = create_list(:user, 2)
+        label.toggle_subscription(subscriber)
+        2.times { label.toggle_subscription(non_subscriber) }
+
+        opts = { label_ids: [label.id, second_label.id] }
+
+        perform_enqueued_jobs do
+          @issue = Issues::UpdateService.new(project, user, opts).execute(issue)
+        end
+
+        @issue.reload
+        should_email(subscriber)
+        should_not_email(non_subscriber)
+      end
+
+      it "does not send notifications for removed labels" do
+        second_label = create(:label)
+        issue.labels << label
+        subscriber, non_subscriber = create_list(:user, 2)
+        label.toggle_subscription(subscriber)
+        2.times { label.toggle_subscription(non_subscriber) }
+
+        opts = { label_ids: [second_label.id] }
+
+        perform_enqueued_jobs do
+          @issue = Issues::UpdateService.new(project, user, opts).execute(issue)
+        end
+
+        @issue.reload
+        should_not_email(subscriber)
+        should_not_email(non_subscriber)
+      end
+    end
+
     context 'when Issue has tasks' do
       before { update_issue({ description: "- [ ] Task 1\n- [ ] Task 2" }) }
 
diff --git a/spec/services/merge_requests/update_service_spec.rb b/spec/services/merge_requests/update_service_spec.rb
index 99703c7a8ec..104e63ccfee 100644
--- a/spec/services/merge_requests/update_service_spec.rb
+++ b/spec/services/merge_requests/update_service_spec.rb
@@ -53,7 +53,7 @@ describe MergeRequests::UpdateService, services: true do
       it { expect(@merge_request.assignee).to eq(user2) }
       it { expect(@merge_request).to be_closed }
       it { expect(@merge_request.labels.count).to eq(1) }
-      it { expect(@merge_request.labels.first.title).to eq('Bug') }
+      it { expect(@merge_request.labels.first.title).to eq(label.name) }
       it { expect(@merge_request.target_branch).to eq('target') }
 
       it 'should execute hooks with update action' do
@@ -176,6 +176,60 @@ describe MergeRequests::UpdateService, services: true do
       end
     end
 
+    context "when the merge request is relabeled" do
+      it "sends notifications for subscribers of newly added labels" do
+        subscriber, non_subscriber = create_list(:user, 2)
+        label.toggle_subscription(subscriber)
+        2.times { label.toggle_subscription(non_subscriber) }
+
+        opts = { label_ids: [label.id] }
+
+        perform_enqueued_jobs do
+          @merge_request = MergeRequests::UpdateService.new(project, user, opts).execute(merge_request)
+        end
+
+        @merge_request.reload
+        should_email(subscriber)
+        should_not_email(non_subscriber)
+      end
+
+      it "does send notifications for existing labels" do
+        second_label = create(:label)
+        merge_request.labels << label
+        subscriber, non_subscriber = create_list(:user, 2)
+        label.toggle_subscription(subscriber)
+        2.times { label.toggle_subscription(non_subscriber) }
+
+        opts = { label_ids: [label.id, second_label.id] }
+
+        perform_enqueued_jobs do
+          @merge_request = MergeRequests::UpdateService.new(project, user, opts).execute(merge_request)
+        end
+
+        @merge_request.reload
+        should_email(subscriber)
+        should_not_email(non_subscriber)
+      end
+
+      it "does not send notifications for removed labels" do
+        second_label = create(:label)
+        merge_request.labels << label
+        subscriber, non_subscriber = create_list(:user, 2)
+        label.toggle_subscription(subscriber)
+        2.times { label.toggle_subscription(non_subscriber) }
+
+        opts = { label_ids: [second_label.id] }
+
+        perform_enqueued_jobs do
+          @merge_request = MergeRequests::UpdateService.new(project, user, opts).execute(merge_request)
+        end
+
+        @merge_request.reload
+        should_not_email(subscriber)
+        should_not_email(non_subscriber)
+      end
+    end
+
     context 'when MergeRequest has tasks' do
       before { update_merge_request({ description: "- [ ] Task 1\n- [ ] Task 2" }) }
 
diff --git a/spec/services/notification_service_spec.rb b/spec/services/notification_service_spec.rb
index 2d0b5df4224..35afa768057 100644
--- a/spec/services/notification_service_spec.rb
+++ b/spec/services/notification_service_spec.rb
@@ -224,6 +224,16 @@ describe NotificationService, services: true do
 
         should_not_email(issue.assignee)
       end
+
+      it "should email subscribers of the issue's labels" do
+        subscriber, non_subscriber = create_list(:user, 2)
+        label = create(:label, issues: [issue])
+        label.toggle_subscription(subscriber)
+        2.times { label.toggle_subscription(non_subscriber) }
+        notification.new_issue(issue, @u_disabled)
+        should_email(subscriber)
+        should_not_email(non_subscriber)
+      end
     end
 
     describe :reassigned_issue do
@@ -326,6 +336,32 @@ describe NotificationService, services: true do
         should_not_email(@u_participating)
       end
     end
+
+    describe :relabel_issue do
+      it "sends email to subscribers of the given labels" do
+        subscriber, non_subscriber = create_list(:user, 2)
+        label = create(:label, issues: [issue])
+        label.toggle_subscription(subscriber)
+        2.times { label.toggle_subscription(non_subscriber) }
+        notification.relabeled_issue(issue, [label], @u_disabled)
+        should_email(subscriber)
+        should_not_email(non_subscriber)
+      end
+
+      it "doesn't send email to anyone but subscribers of the given labels" do
+        label = create(:label, issues: [issue])
+        notification.relabeled_issue(issue, [label], @u_disabled)
+
+        should_not_email(issue.assignee)
+        should_not_email(issue.author)
+        should_not_email(@u_watcher)
+        should_not_email(@u_participant_mentioned)
+        should_not_email(@subscriber)
+        should_not_email(@watcher_and_subscriber)
+        should_not_email(@unsubscriber)
+        should_not_email(@u_participating)
+      end
+    end
   end
 
   describe 'Merge Requests' do
@@ -349,6 +385,17 @@ describe NotificationService, services: true do
         should_not_email(@u_participating)
         should_not_email(@u_disabled)
       end
+
+      it "should email subscribers of the MR's labels" do
+        subscriber, non_subscriber = create_list(:user, 2)
+        label = create(:label)
+        merge_request.labels << label
+        label.toggle_subscription(subscriber)
+        2.times { label.toggle_subscription(non_subscriber) }
+        notification.new_merge_request(merge_request, @u_disabled)
+        should_email(subscriber)
+        should_not_email(non_subscriber)
+      end
     end
 
     describe :reassigned_merge_request do
@@ -410,6 +457,34 @@ describe NotificationService, services: true do
         should_not_email(@u_disabled)
       end
     end
+
+    describe :relabel_merge_request do
+      it "sends email to subscribers of the given labels" do
+        subscriber, non_subscriber = create_list(:user, 2)
+        label = create(:label)
+        merge_request.labels << label
+        label.toggle_subscription(subscriber)
+        2.times { label.toggle_subscription(non_subscriber) }
+        notification.relabeled_merge_request(merge_request, [label], @u_disabled)
+        should_email(subscriber)
+        should_not_email(non_subscriber)
+      end
+
+      it "doesn't send email to anyone but subscribers of the given labels" do
+        label = create(:label)
+        merge_request.labels << label
+        notification.relabeled_merge_request(merge_request, [label], @u_disabled)
+
+        should_not_email(merge_request.assignee)
+        should_not_email(merge_request.author)
+        should_not_email(@u_watcher)
+        should_not_email(@u_participant_mentioned)
+        should_not_email(@subscriber)
+        should_not_email(@watcher_and_subscriber)
+        should_not_email(@unsubscriber)
+        should_not_email(@u_participating)
+      end
+    end
   end
 
   describe 'Projects' do
@@ -467,16 +542,4 @@ describe NotificationService, services: true do
     # Make the watcher a subscriber to detect dupes
     issuable.subscriptions.create(user: @watcher_and_subscriber, subscribed: true)
   end
-
-  def sent_to_user?(user)
-    ActionMailer::Base.deliveries.map(&:to).flatten.count(user.email) == 1
-  end
-
-  def should_email(user)
-    expect(sent_to_user?(user)).to be_truthy
-  end
-
-  def should_not_email(user)
-    expect(sent_to_user?(user)).to be_falsey
-  end
 end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 7d939ca7509..596d607f2a1 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -32,6 +32,7 @@ RSpec.configure do |config|
   config.include LoginHelpers,        type: :feature
   config.include LoginHelpers,        type: :request
   config.include StubConfiguration
+  config.include EmailHelpers
   config.include RelativeUrl,         type: feature
   config.include TestEnv
   config.include ActiveJob::TestHelper
diff --git a/spec/support/email_helpers.rb b/spec/support/email_helpers.rb
new file mode 100644
index 00000000000..a85ab22ce36
--- /dev/null
+++ b/spec/support/email_helpers.rb
@@ -0,0 +1,13 @@
+module EmailHelpers
+  def sent_to_user?(user)
+    ActionMailer::Base.deliveries.map(&:to).flatten.count(user.email) == 1
+  end
+
+  def should_email(user)
+    expect(sent_to_user?(user)).to be_truthy
+  end
+
+  def should_not_email(user)
+    expect(sent_to_user?(user)).to be_falsey
+  end
+end