Refactors ActiveJob to SidekiqWorker: Follows::SendEmailNotificationWorker (#5322) [deploy]

* Refactors ActiveJob to SidekiqWorker: Follows::SendEmailNotificationWorker
* improves naming of User#receives_follower_email_notifications?
* adjust expect count for spec SendEmailNotificationWorker

app/jobs/follows/send_email_notification_job.rb

@@ -1,3 +1,4 @@
+# @TODO: to be removed in favor of `app/workers/follows/send_email_notification_worker.rb`
 module Follows
   class SendEmailNotificationJob < ApplicationJob
     queue_as :send_follow_email_notification

app/mailers/notify_mailer.rb

@@ -1,4 +1,8 @@
 class NotifyMailer < ApplicationMailer
+  SUBJECTS = {
+    new_follower_email: "just followed you on dev.to".freeze
+  }.freeze
+
   def new_reply_email(comment)
     @user = comment.parent_user
     return if RateLimitChecker.new.limit_by_email_recipient_address(@user.email)
@@ -15,7 +19,7 @@ class NotifyMailer < ApplicationMailer
     @follower = follow.follower
     @unsubscribe = generate_unsubscribe_token(@user.id, :email_follower_notifications)
 
-    mail(to: @user.email, subject: "#{@follower.name} just followed you on dev.to")
+    mail(to: @user.email, subject: "#{@follower.name} #{SUBJECTS[__method__]}")
   end
 
   def new_mention_email(mention)

app/models/follow.rb

@@ -46,7 +46,7 @@ class Follow < ApplicationRecord
   def send_email_notification
     return unless followable.class.name == "User" && followable.email?
 
-    Follows::SendEmailNotificationJob.perform_later(id)
+    Follows::SendEmailNotificationWorker.perform_async(id)
   end
 
   def modify_chat_channel_status

app/models/user.rb

@@ -451,6 +451,11 @@ class User < ApplicationRecord
     credits.unspent.size >= num_credits_needed
   end
 
+  def receives_follower_email_notifications?
+    email.present? &&
+      email_follower_notifications
+  end
+
   private
 
   def index_id

app/workers/follows/send_email_notification_worker.rb

@@ -0,0 +1,17 @@
+module Follows
+  class SendEmailNotificationWorker
+    include Sidekiq::Worker
+    sidekiq_options queue: :mailers, retry: 10
+
+    def perform(follow_id, mailer = NotifyMailer.name)
+      follow = Follow.find_by(id: follow_id, followable_type: "User")
+      return unless follow&.followable.present? && follow.followable.receives_follower_email_notifications?
+
+      return if EmailMessage.where(user_id: follow.followable_id).
+        where("sent_at > ?", rand(15..35).hours.ago).
+        where("subject LIKE ?", "%#{NotifyMailer::SUBJECTS[:new_follower_email]}").exists?
+
+      mailer.constantize.new_follower_email(follow).deliver
+    end
+  end
+end

spec/models/follow_spec.rb

@@ -26,10 +26,10 @@ RSpec.describe Follow, type: :model do
       end.to have_enqueued_job(Follows::CreateChatChannelJob)
     end
 
-    it "enqueues send notification job" do
+    it "enqueues send notification worker" do
       expect do
         described_class.create(follower: user, followable: user_2)
-      end.to have_enqueued_job(Follows::SendEmailNotificationJob)
+      end.to change(Follows::SendEmailNotificationWorker.jobs, :size).by(1)
     end
   end
 
@@ -73,7 +73,7 @@ RSpec.describe Follow, type: :model do
     it "sends an email notification" do
       user_2.update_column(:email_follower_notifications, true)
       expect do
-        perform_enqueued_jobs do
+        Sidekiq::Testing.inline! do
           described_class.create!(follower: user, followable: user_2)
         end
       end.to change(EmailMessage, :count).by(1)

spec/models/user_spec.rb

@@ -727,4 +727,21 @@ RSpec.describe User, type: :model do
       expect(user.enough_credits?(1)).to be(true)
     end
   end
+
+  describe "#receives_follower_email_notifications?" do
+    it "returns false if user has no email" do
+      user.assign_attributes(email: nil)
+      expect(user.receives_follower_email_notifications?).to be(false)
+    end
+
+    it "returns false if user opted out from follower notifications" do
+      user.assign_attributes(email_follower_notifications: false)
+      expect(user.receives_follower_email_notifications?).to be(false)
+    end
+
+    it "returns true if user opted in from follower notifications and has an email" do
+      user.assign_attributes(email_follower_notifications: true)
+      expect(user.receives_follower_email_notifications?).to be(true)
+    end
+  end
 end

spec/workers/follows/send_email_notification_worker_spec.rb

@@ -0,0 +1,56 @@
+require "rails_helper"
+
+class MockMailer
+  def self.deliver; end
+end
+
+RSpec.describe Follows::SendEmailNotificationWorker, type: :worker do
+  subject(:worker) { described_class }
+
+  let_it_be(:user) { create(:user) }
+  let_it_be(:user2) { create(:user) }
+  let_it_be(:follow) { create(:follow, follower: user, followable: user2) }
+
+  describe "#perform" do
+    before do
+      allow(NotifyMailer).to receive(:new_follower_email).and_return(MockMailer)
+      allow(MockMailer).to receive(:deliver)
+      worker.perform_async(follow_id)
+    end
+
+    context "with follow" do
+      let(:follow_id) { follow.id }
+
+      it "sends a new_follower_email" do
+        user2.update_column(:email_follower_notifications, true)
+        worker.drain
+
+        expect(MockMailer).to have_received(:deliver).once
+      end
+
+      it "doesn't send an email if user has disabled notifications" do
+        user2.update_column(:email_follower_notifications, false)
+        worker.drain
+
+        expect(MockMailer).not_to have_received(:deliver)
+      end
+
+      it "doesn't create an EmailMessage if it already exists" do
+        subject = "#{user.username} just followed you on dev.to"
+        EmailMessage.create!(user_id: user2.id, sent_at: Time.current, subject: subject)
+
+        worker.drain
+
+        expect(MockMailer).not_to have_received(:deliver)
+      end
+    end
+
+    context "without follow" do
+      let(:follow_id) { nil }
+
+      it "does not break" do
+        expect { worker.drain }.not_to raise_error
+      end
+    end
+  end
+end