Allow empty recipient list when pusher is added

Closes #13574

CHANGELOG

@@ -60,6 +60,7 @@ v 8.7.0 (unreleased)
   - API: Expose 'updated_at' for issue, snippet, and merge request notes (Robert Schilling)
   - API: User can leave a project through the API when not master or owner. !3613
   - Fix repository cache invalidation issue when project is recreated with an empty repo (Stan Hu)
+  - Fix: Allow empty recipients list for builds emails service when pushed is added (Frank Groeneveld)
 
 v 8.6.6
   - Fix error on language detection when repository has no HEAD (e.g., master branch). !3654 (Jeroen Bobbeldijk)

app/models/project_services/builds_email_service.rb

@@ -23,7 +23,7 @@ class BuildsEmailService < Service
   prop_accessor :recipients
   boolean_accessor :add_pusher
   boolean_accessor :notify_only_broken_builds
-  validates :recipients, presence: true, if: :activated?
+  validates :recipients, presence: true, if: ->(s) { s.activated? && !s.add_pusher? }
 
   def initialize_properties
     if properties.nil?
@@ -87,10 +87,14 @@ class BuildsEmailService < Service
   end
 
   def all_recipients(data)
-    all_recipients = recipients.split(',').compact.reject(&:blank?)
+    all_recipients = []
+
+    unless recipients.blank?
+      all_recipients += recipients.split(',').compact.reject(&:blank?)
+    end
 
     if add_pusher? && data[:user][:email]
-      all_recipients << "#{data[:user][:email]}"
+      all_recipients << data[:user][:email]
     end
 
     all_recipients

spec/models/project_services/builds_email_service_spec.rb

@@ -3,9 +3,10 @@ require 'spec_helper'
 describe BuildsEmailService do
   let(:build) { create(:ci_build) }
   let(:data) { Gitlab::BuildDataBuilder.build(build) }
-  let(:service) { BuildsEmailService.new }
+  let!(:project) { create(:project, :public, ci_id: 1) }
+  let(:service) { described_class.new(project: project, active: true) }
 
-  describe :execute do
+  describe '#execute' do
     it 'sends email' do
       service.recipients = 'test@gitlab.com'
       data[:build_status] = 'failed'
@@ -40,4 +41,36 @@ describe BuildsEmailService do
       service.execute(data)
     end
   end
+
+  describe 'validations' do
+
+    context 'when pusher is not added' do
+      before { service.add_pusher = false }
+
+      it 'does not allow empty recipient input' do
+        service.recipients = ''
+        expect(service.valid?).to be false
+      end
+
+      it 'does allow non-empty recipient input' do
+        service.recipients = 'test@example.com'
+        expect(service.valid?).to be true
+      end
+
+    end
+
+    context 'when pusher is added' do
+      before { service.add_pusher = true }
+
+      it 'does allow empty recipient input' do
+        service.recipients = ''
+        expect(service.valid?).to be true
+      end
+
+      it 'does allow non-empty recipient input' do
+        service.recipients = 'test@example.com'
+        expect(service.valid?).to be true
+      end
+    end
+  end
 end