Only generate repository push email once

The repository push email can be very expensive to generate, especially
with syntax-highlighted diffs. Instead of generating the email for each
recipient, generate one email object and reset the Message-Id and To
headers for each recipient. (Cloning would also be expensive in the case
of large emails, although probably not as bad as generating from
scratch.)

1 files changed, 51 insertions, 14 deletions

diff --git a/spec/workers/emails_on_push_worker_spec.rb b/spec/workers/emails_on_push_worker_spec.rb
index 3600c771075..439da765c2c 100644
--- a/spec/workers/emails_on_push_worker_spec.rb
+++ b/spec/workers/emails_on_push_worker_spec.rb
@@ -6,29 +6,66 @@ describe EmailsOnPushWorker do
   let(:project) { create(:project) }
   let(:user) { create(:user) }
   let(:data) { Gitlab::PushDataBuilder.build_sample(project, user) }
+  let(:recipients) { user.email }
+  let(:perform) { subject.perform(project.id, recipients, data.stringify_keys) }
 
   subject { EmailsOnPushWorker.new }
 
-  before do
-    allow(Project).to receive(:find).and_return(project)
-  end
-
   describe "#perform" do
-    it "sends mail" do
-      subject.perform(project.id, user.email, data.stringify_keys)
+    context "when there are no errors in sending" do
+      let(:email) { ActionMailer::Base.deliveries.last }
+
+      before { perform }
 
-      email = ActionMailer::Base.deliveries.last
-      expect(email.subject).to include('Change some files')
-      expect(email.to).to eq([user.email])
+      it "sends a mail with the correct subject" do
+        expect(email.subject).to include('Change some files')
+      end
+
+      it "sends the mail to the correct recipient" do
+        expect(email.to).to eq([user.email])
+      end
     end
 
-    it "gracefully handles an input SMTP error" do
-      ActionMailer::Base.deliveries.clear
-      allow(Notify).to receive(:repository_push_email).and_raise(Net::SMTPFatalError)
+    context "when there is an SMTP error" do
+      before do
+        ActionMailer::Base.deliveries.clear
+        allow(Notify).to receive(:repository_push_email).and_raise(Net::SMTPFatalError)
+        perform
+      end
+
+      it "gracefully handles an input SMTP error" do
+        expect(ActionMailer::Base.deliveries.count).to eq(0)
+      end
+    end
+
+    context "when there are multiple recipients" do
+      let(:recipients) do
+        1.upto(5).map { |i| user.email.sub('@', "+#{i}@") }.join("\n")
+      end
+
+      before do
+        # This is a hack because we modify the mail object before sending, for efficency,
+        # but the TestMailer adapter just appends the objects to an array. To clone a mail
+        # object, create a new one!
+        #   https://github.com/mikel/mail/issues/314#issuecomment-12750108
+        allow_any_instance_of(Mail::TestMailer).to receive(:deliver!).and_wrap_original do |original, mail|
+          original.call(Mail.new(mail.encoded))
+        end
+
+        ActionMailer::Base.deliveries.clear
+      end
 
-      subject.perform(project.id, user.email, data.stringify_keys)
+      it "sends the mail to each of the recipients" do
+        perform
+        expect(ActionMailer::Base.deliveries.count).to eq(5)
+        expect(ActionMailer::Base.deliveries.map(&:to).flatten).to contain_exactly(*recipients.split)
+      end
 
-      expect(ActionMailer::Base.deliveries.count).to eq(0)
+      it "only generates the mail once" do
+        expect(Notify).to receive(:repository_push_email).once.and_call_original
+        expect(Premailer::Rails::CustomizedPremailer).to receive(:new).once.and_call_original
+        perform
+      end
     end
   end
 end