Add invite email experiment

This creates an experiment for a new invite email design that is
simpler for our users and only has one call to action instead of
multiple. In the first iteration, this is only for new users and
we're tracking how many more users accept the invitation with
the new design compared to the old one.

.haml-lint_todo.yml

@@ -117,6 +117,7 @@ linters:
       - "app/views/import/bitbucket_server/status.html.haml"
       - "app/views/invites/show.html.haml"
       - "app/views/layouts/_mailer.html.haml"
+      - "app/views/layouts/experiment_mailer.html.haml"
       - "app/views/layouts/header/_default.html.haml"
       - "app/views/layouts/header/_new_dropdown.haml"
       - "app/views/layouts/notify.html.haml"

app/assets/stylesheets/mailer.scss

@@ -48,6 +48,22 @@ a {
   font-weight: 500;
 }
 
+.invite-header {
+  margin-top: 0;
+}
+
+.invite-actions {
+  margin-top: 24px;
+}
+
+.invite-btn-join {
+  border-radius: $border-radius-default;
+  padding: $gl-btn-vert-padding $gl-btn-horz-padding;
+  cursor: pointer;
+  background-color: $purple;
+  color: $white;
+}
+
 tr td {
   font-family: $mailer-font;
 }

app/controllers/invites_controller.rb

@@ -12,11 +12,13 @@ class InvitesController < ApplicationController
   respond_to :html
 
   def show
+    track_experiment('opened')
     accept if skip_invitation_prompt?
   end
 
   def accept
     if member.accept_invite!(current_user)
+      track_experiment('accepted')
       redirect_to invite_details[:path], notice: _("You have been granted %{member_human_access} access to %{title} %{name}.") %
         { member_human_access: member.human_access, title: invite_details[:title], name: invite_details[:name] }
     else
@@ -96,4 +98,17 @@ class InvitesController < ApplicationController
                           }
                         end
   end
+
+  def track_experiment(action)
+    return unless params[:new_user_invite]
+
+    property = params[:new_user_invite] == 'experiment' ? 'experiment_group' : 'control_group'
+
+    Gitlab::Tracking.event(
+      Gitlab::Experimentation::EXPERIMENTS[:invite_email][:tracking_category],
+      action,
+      property: property,
+      value: Digest::MD5.hexdigest(member.to_global_id.to_s)
+    )
+  end
 end

app/mailers/emails/members.rb

@@ -51,9 +51,32 @@ module Emails
 
       return unless member_exists?
 
-      member_email_with_layout(
-        to: member.invite_email,
-        subject: subject("Invitation to join the #{member_source.human_name} #{member_source.model_name.singular}"))
+      subject_line = subject("Invitation to join the #{member_source.human_name} #{member_source.model_name.singular}")
+
+      if member.invite_to_unknown_user? && Feature.enabled?(:invite_email_experiment)
+        subject_line = subject("#{member.created_by.name} invited you to join GitLab") if member.created_by
+        @invite_url_params = { new_user_invite: 'experiment' }
+
+        member_email_with_layout(
+          to: member.invite_email,
+          subject: subject_line,
+          template: 'member_invited_email_experiment',
+          layout: 'experiment_mailer'
+        )
+
+        Gitlab::Tracking.event(Gitlab::Experimentation::EXPERIMENTS[:invite_email][:tracking_category], 'sent', property: 'experiment_group')
+      else
+        @invite_url_params = member.invite_to_unknown_user? ? { new_user_invite: 'control' } : {}
+
+        member_email_with_layout(
+          to: member.invite_email,
+          subject: subject_line
+        )
+
+        if member.invite_to_unknown_user?
+          Gitlab::Tracking.event(Gitlab::Experimentation::EXPERIMENTS[:invite_email][:tracking_category], 'sent', property: 'control_group')
+        end
+      end
     end
 
     def member_invite_accepted_email(member_source_type, member_id)
@@ -107,10 +130,15 @@ module Emails
       @member_source_type.classify.constantize
     end
 
-    def member_email_with_layout(to:, subject:)
+    def member_email_with_layout(to:, subject:, template: nil, layout: 'mailer')
       mail(to: to, subject: subject) do |format|
-        format.html { render layout: 'mailer' }
-        format.text { render layout: 'mailer' }
+        if template
+          format.html { render template, layout: layout }
+          format.text { render template, layout: layout }
+        else
+          format.html { render layout: layout }
+          format.text { render layout: layout }
+        end
       end
     end
   end

app/models/member.rb

@@ -395,6 +395,10 @@ class Member < ApplicationRecord
     end
   end
 
+  def invite_to_unknown_user?
+    invite? && user_id.nil?
+  end
+
   private
 
   def send_invite

app/views/invites/show.html.haml

@@ -25,5 +25,5 @@
 
 - if !member?
   .actions
-    = link_to _("Accept invitation"), accept_invite_url(@token), method: :post, class: "btn btn-success"
+    = link_to _("Accept invitation"), accept_invite_url(@token, new_user_invite: params[:new_user_invite]), method: :post, class: "btn btn-success"
     = link_to _("Decline"), decline_invite_url(@token), method: :post, class: "btn btn-danger gl-ml-3"

app/views/layouts/experiment_mailer.html.haml

+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+%html{ lang: "en" }
+  %head
+    %meta{ content: "text/html; charset=UTF-8", "http-equiv" => "Content-Type" }/
+    %meta{ content: "width=device-width, initial-scale=1", name: "viewport" }/
+    %meta{ content: "IE=edge", "http-equiv" => "X-UA-Compatible" }/
+    %title= message.subject
+
+    -# Avoid premailer processing of client-specific styles (@media tag not supported)
+    -# We need to inline the contents here because mail clients (e.g. iOS Mail, Outlook)
+    -# do not support linked stylesheets.
+    %style{ type: 'text/css', 'data-premailer': 'ignore' }
+      = asset_to_string('mailer_client_specific.css').html_safe
+
+    = stylesheet_link_tag 'mailer.css'
+  %body
+    %table#body{ border: "0", cellpadding: "0", cellspacing: "0" }
+      %tbody
+        %tr.line
+          %td
+        %tr.header
+          %td
+            = html_header_message
+            = header_logo
+        %tr
+          %td
+            %table.wrapper{ border: "0", cellpadding: "0", cellspacing: "0" }
+              %tbody
+                %tr
+                  %td.wrapper-cell{ style: "padding: 0" }
+                    %table.content{ border: "0", cellpadding: "0", cellspacing: "0" }
+                      %tbody
+                        = yield
+
+        = render_if_exists 'layouts/mailer/additional_text'
+
+        %tr.footer
+          %td{ style: "padding: 24px 0" }
+            %img{ alt: "GitLab", height: "33", width: "90", src: image_url('mailers/gitlab_footer_logo.gif') }
+            %p{ style: "color: #949ba5; max-width: 640px; margin: 0 auto; text-align: left; font-size: 12px;" }
+              GitLab is a complete DevOps platform, delivered as a single application, fundamentally changing the way
+              %br
+              Development, Security, and Ops teams collaborate.
+
+        = yield :additional_footer
+        %tr
+          %td.footer-message
+            = html_footer_message

app/views/notify/member_invited_email.html.haml

@@ -10,7 +10,7 @@
       #{member_source.model_name.singular} as #{content_tag :span, member.human_access, class: :highlight}.
 
     %p
-      = link_to 'Accept invitation', invite_url(@token)
+      = link_to 'Accept invitation', invite_url(@token, @invite_url_params)
       or
       = link_to 'decline', decline_invite_url(@token)
 

app/views/notify/member_invited_email.text.erb

 You have been invited <%= "by #{sanitize_name(member.created_by.name)} " if member.created_by %>to join the <%= member_source.human_name %> <%= member_source.model_name.singular %> as <%= member.human_access %>.
 
-Accept invitation: <%= invite_url(@token) %>
+Accept invitation: <%= invite_url(@token, @invite_url_params) %>
 Decline invitation: <%= decline_invite_url(@token) %>

app/views/notify/member_invited_email_experiment.html.haml

+%tr
+  %td.text-content
+    %h2.invite-header
+      = s_('InviteEmail|You are invited!')
+    %p
+      - if member.created_by
+        = html_escape(s_("InviteEmail|%{inviter} invited you")) % { inviter: (link_to member.created_by.name, user_url(member.created_by)).html_safe }
+      = html_escape(s_("InviteEmail|to join the %{strong_start}%{project_or_group_name}%{strong_end}")) % { strong_start: '<strong>'.html_safe, strong_end: '</strong>'.html_safe, project_or_group_name: member_source.human_name }
+      %br
+      = s_("InviteEmail|%{project_or_group} as a %{role}") % { project_or_group: member_source.model_name.singular, role: member.human_access.downcase }
+    %p.invite-actions
+      = link_to s_('InviteEmail|Join now'), invite_url(@token, @invite_url_params), class: 'invite-btn-join'

app/views/notify/member_invited_email_experiment.text.erb

+<% project_and_role = s_('InviteEmail|to join the %{project_or_group_name} %{project_or_group} as a %{role}') \
+  % { project_or_group_name: member_source.human_name, project_or_group: member_source.model_name.singular, role: member.human_access.downcase } %>
+
+<% if member.created_by %>
+<%= s_('InviteEmail|%{inviter} invited you') % { inviter: sanitize_name(member.created_by.name) } %> <%= project_and_role %>
+<% else %>
+<%= s_('InviteEmail|You have been invited') %> <%= project_and_role %>
+<% end %>
+
+Join now: <%= invite_url(@token, @invite_url_params) %>

lib/gitlab/experimentation.rb

@@ -62,6 +62,9 @@ module Gitlab
       },
       customize_homepage: {
         tracking_category: 'Growth::Expansion::Experiment::CustomizeHomepage'
+      },
+      invite_email: {
+        tracking_category: 'Growth::Acquisition::Experiment::InviteEmail'
       }
     }.freeze
 

locale/gitlab.pot

@@ -13414,6 +13414,27 @@ msgstr ""
 msgid "Invite teammates (optional)"
 msgstr ""
 
+msgid "InviteEmail|%{inviter} invited you"
+msgstr ""
+
+msgid "InviteEmail|%{project_or_group} as a %{role}"
+msgstr ""
+
+msgid "InviteEmail|Join now"
+msgstr ""
+
+msgid "InviteEmail|You are invited!"
+msgstr ""
+
+msgid "InviteEmail|You have been invited"
+msgstr ""
+
+msgid "InviteEmail|to join the %{project_or_group_name} %{project_or_group} as a %{role}"
+msgstr ""
+
+msgid "InviteEmail|to join the %{strong_start}%{project_or_group_name}%{strong_end}"
+msgstr ""
+
 msgid "Invited"
 msgstr ""
 

spec/controllers/invites_controller_spec.rb

@@ -7,6 +7,7 @@ RSpec.describe InvitesController do
   let_it_be(:user) { create(:user) }
   let(:member) { create(:project_member, :invited, invite_token: token, invite_email: user.email) }
   let(:project_members) { member.source.users }
+  let(:md5_member_global_id) { Digest::MD5.hexdigest(member.to_global_id.to_s) }
 
   before do
     controller.instance_variable_set(:@member, member)
@@ -14,9 +15,13 @@ RSpec.describe InvitesController do
   end
 
   describe 'GET #show' do
+    let(:params) { { id: token } }
+
+    subject(:request) { get :show, params: params }
+
     it 'accepts user if invite email matches signed in user' do
       expect do
-        get :show, params: { id: token }
+        request
       end.to change { project_members.include?(user) }.from(false).to(true)
 
       expect(response).to have_gitlab_http_status(:found)
@@ -27,11 +32,105 @@ RSpec.describe InvitesController do
       member.invite_email = 'bogus@email.com'
 
       expect do
-        get :show, params: { id: token }
+        request
       end.not_to change { project_members.include?(user) }
 
       expect(response).to have_gitlab_http_status(:ok)
       expect(flash[:notice]).to be_nil
     end
+
+    context 'when new_user_invite is not set' do
+      it 'does not track the user as experiment group' do
+        expect(Gitlab::Tracking).not_to receive(:event)
+
+        request
+      end
+    end
+
+    context 'when new_user_invite is experiment' do
+      let(:params) { { id: token, new_user_invite: 'experiment' } }
+
+      it 'tracks the user as experiment group' do
+        expect(Gitlab::Tracking).to receive(:event).with(
+          'Growth::Acquisition::Experiment::InviteEmail',
+          'opened',
+          property: 'experiment_group',
+          value: md5_member_global_id
+        )
+        expect(Gitlab::Tracking).to receive(:event).with(
+          'Growth::Acquisition::Experiment::InviteEmail',
+          'accepted',
+          property: 'experiment_group',
+          value: md5_member_global_id
+        )
+
+        request
+      end
+    end
+
+    context 'when new_user_invite is control' do
+      let(:params) { { id: token, new_user_invite: 'control' } }
+
+      it 'tracks the user as control group' do
+        expect(Gitlab::Tracking).to receive(:event).with(
+          'Growth::Acquisition::Experiment::InviteEmail',
+          'opened',
+          property: 'control_group',
+          value: md5_member_global_id
+        )
+        expect(Gitlab::Tracking).to receive(:event).with(
+          'Growth::Acquisition::Experiment::InviteEmail',
+          'accepted',
+          property: 'control_group',
+          value: md5_member_global_id
+        )
+
+        request
+      end
+    end
+  end
+
+  describe 'POST #accept' do
+    let(:params) { { id: token } }
+
+    subject(:request) { post :accept, params: params }
+
+    context 'when new_user_invite is not set' do
+      it 'does not track an event' do
+        expect(Gitlab::Tracking).not_to receive(:event)
+
+        request
+      end
+    end
+
+    context 'when new_user_invite is experiment' do
+      let(:params) { { id: token, new_user_invite: 'experiment' } }
+
+      it 'tracks the user as experiment group' do
+        expect(Gitlab::Tracking).to receive(:event).with(
+          'Growth::Acquisition::Experiment::InviteEmail',
+          'accepted',
+          property: 'experiment_group',
+          value: md5_member_global_id
+        )
+
+        request
+      end
+    end
+
+    context 'when new_user_invite is control' do
+      let(:params) { { id: token, new_user_invite: 'control' } }
+
+      it 'tracks the user as control group' do
+        expect(Gitlab::Tracking).to receive(:event).with(
+          'Growth::Acquisition::Experiment::InviteEmail',
+          'accepted',
+          property: 'control_group',
+          value: md5_member_global_id
+        )
+
+        request
+      end
+    end
   end
 end

spec/mailers/notify_spec.rb

@@ -868,36 +868,116 @@ RSpec.describe Notify do
       end
     end
 
-    def invite_to_project(project, inviter:)
+    def invite_to_project(project, inviter:, user: nil)
       create(
         :project_member,
         :developer,
         project: project,
         invite_token: '1234',
         invite_email: 'toto@example.com',
-        user: nil,
+        user: user,
         created_by: inviter
       )
     end
 
     describe 'project invitation' do
       let(:maintainer) { create(:user).tap { |u| project.add_maintainer(u) } }
-      let(:project_member) { invite_to_project(project, inviter: maintainer) }
+      let(:project_member) { invite_to_project(project, inviter: inviter) }
+      let(:inviter) { maintainer }
 
       subject { described_class.member_invited_email('project', project_member.id, project_member.invite_token) }
 
-      it_behaves_like 'an email sent from GitLab'
-      it_behaves_like 'it should not have Gmail Actions links'
-      it_behaves_like "a user cannot unsubscribe through footer link"
-      it_behaves_like 'appearance header and footer enabled'
-      it_behaves_like 'appearance header and footer not enabled'
+      context 'when invite_email_experiment is disabled' do
+        before do
+          stub_feature_flags(invite_email_experiment: false)
+        end
 
-      it 'contains all the useful information' do
-        is_expected.to have_subject "Invitation to join the #{project.full_name} project"
-        is_expected.to have_body_text project.full_name
-        is_expected.to have_body_text project.full_name
-        is_expected.to have_body_text project_member.human_access
-        is_expected.to have_body_text project_member.invite_token
+        it_behaves_like 'an email sent from GitLab'
+        it_behaves_like 'it should not have Gmail Actions links'
+        it_behaves_like "a user cannot unsubscribe through footer link"
+        it_behaves_like 'appearance header and footer enabled'
+        it_behaves_like 'appearance header and footer not enabled'
+
+        it 'contains all the useful information' do
+          is_expected.to have_subject "Invitation to join the #{project.full_name} project"
+          is_expected.to have_body_text project.full_name
+          is_expected.to have_body_text project_member.human_access
+          is_expected.to have_body_text project_member.invite_token
+        end
+
+        context 'when member is invited via an email address' do
+          it 'does add a param to the invite link' do
+            is_expected.to have_body_text 'new_user_invite=control'
+          end
+
+          it 'tracks an event' do
+            expect(Gitlab::Tracking).to receive(:event).with(
+              'Growth::Acquisition::Experiment::InviteEmail',
+              'sent',
+              property: 'control_group'
+            )
+
+            subject.deliver_now
+          end
+        end
+
+        context 'when member is already a user' do
+          let(:project_member) { invite_to_project(project, inviter: maintainer, user: create(:user)) }
+
+          it 'does not add a param to the invite link' do
+            is_expected.not_to have_body_text 'new_user_invite'
+          end
+
+          it 'does not track an event' do
+            expect(Gitlab::Tracking).not_to receive(:event)
+
+            subject.deliver_now
+          end
+        end
+      end
+
+      context 'when invite_email_experiment is enabled' do
+        before do
+          stub_feature_flags(invite_email_experiment: true)
+        end
+
+        it_behaves_like 'an email sent from GitLab'
+        it_behaves_like 'it should not have Gmail Actions links'
+        it_behaves_like "a user cannot unsubscribe through footer link"
+
+        context 'when there is no inviter' do
+          let(:inviter) { nil }
+
+          it 'contains all the useful information' do
+            is_expected.to have_subject "Invitation to join the #{project.full_name} project"
+            is_expected.to have_body_text project.full_name
+            is_expected.to have_body_text project_member.human_access.downcase
+            is_expected.to have_body_text project_member.invite_token
+          end
+        end
+
+        context 'when there is an inviter' do
+          it 'contains all the useful information' do
+            is_expected.to have_subject "#{inviter.name} invited you to join GitLab"
+            is_expected.to have_body_text project.full_name
+            is_expected.to have_body_text project_member.human_access.downcase
+            is_expected.to have_body_text project_member.invite_token
+          end
+        end
+
+        it 'adds a param to the invite link' do
+          is_expected.to have_body_text 'new_user_invite=experiment'
+        end
+
+        it 'tracks an event' do
+          expect(Gitlab::Tracking).to receive(:event).with(
+            'Growth::Acquisition::Experiment::InviteEmail',
+            'sent',
+            property: 'experiment_group'
+          )
+
+          subject.deliver_now
+        end
       end
     end
 
@@ -1416,37 +1496,115 @@ RSpec.describe Notify do
       end
     end
 
-    def invite_to_group(group, inviter:)
+    def invite_to_group(group, inviter:, user: nil)
       create(
         :group_member,
         :developer,
         group: group,
         invite_token: '1234',
         invite_email: 'toto@example.com',
-        user: nil,
+        user: user,
         created_by: inviter
       )
     end
 
     describe 'group invitation' do
       let(:owner) { create(:user).tap { |u| group.add_user(u, Gitlab::Access::OWNER) } }
-      let(:group_member) { invite_to_group(group, inviter: owner) }
+      let(:group_member) { invite_to_group(group, inviter: inviter) }
+      let(:inviter) { owner }
 
       subject { described_class.member_invited_email('group', group_member.id, group_member.invite_token) }
 
-      it_behaves_like 'an email sent from GitLab'
-      it_behaves_like 'it should not have Gmail Actions links'
-      it_behaves_like "a user cannot unsubscribe through footer link"
-      it_behaves_like 'appearance header and footer enabled'
-      it_behaves_like 'appearance header and footer not enabled'
-      it_behaves_like 'it requires a group'
+      context 'when invite_email_experiment is disabled' do
+        before do
+          stub_feature_flags(invite_email_experiment: false)
+        end
 
-      it 'contains all the useful information' do
-        is_expected.to have_subject "Invitation to join the #{group.name} group"
-        is_expected.to have_body_text group.name
-        is_expected.to have_body_text group.web_url
-        is_expected.to have_body_text group_member.human_access
-        is_expected.to have_body_text group_member.invite_token
+        it_behaves_like 'an email sent from GitLab'
+        it_behaves_like 'it should not have Gmail Actions links'
+        it_behaves_like "a user cannot unsubscribe through footer link"
+        it_behaves_like 'appearance header and footer enabled'
+        it_behaves_like 'appearance header and footer not enabled'
+        it_behaves_like 'it requires a group'
+
+        it 'contains all the useful information' do
+          is_expected.to have_subject "Invitation to join the #{group.name} group"
+          is_expected.to have_body_text group.name
+          is_expected.to have_body_text group.web_url
+          is_expected.to have_body_text group_member.human_access
+          is_expected.to have_body_text group_member.invite_token
+        end
+
+        context 'when member is invited via an email address' do
+          it 'does add a param to the invite link' do
+            is_expected.to have_body_text 'new_user_invite=control'
+          end
+
+          it 'tracks an event' do
+            expect(Gitlab::Tracking).to receive(:event).with(
+              'Growth::Acquisition::Experiment::InviteEmail',
+              'sent',
+              property: 'control_group'
+            )
+
+            subject.deliver_now
+          end
+        end
+
+        context 'when member is already a user' do
+          let(:group_member) { invite_to_group(group, inviter: owner, user: create(:user)) }
+
+          it 'does not add a param to the invite link' do
+            is_expected.not_to have_body_text 'new_user_invite'
+          end
+
+          it 'does not track an event' do
+            expect(Gitlab::Tracking).not_to receive(:event)
+
+            subject.deliver_now
+          end
+        end
+      end
+
+      context 'when invite_email_experiment is enabled' do
+        it_behaves_like 'an email sent from GitLab'
+        it_behaves_like 'it should not have Gmail Actions links'
+        it_behaves_like "a user cannot unsubscribe through footer link"
+        it_behaves_like 'it requires a group'
+
+        context 'when there is no inviter' do
+          let(:inviter) { nil }
+
+          it 'contains all the useful information' do
+            is_expected.to have_subject "Invitation to join the #{group.name} group"
+            is_expected.to have_body_text group.name
+            is_expected.to have_body_text group_member.human_access.downcase
+            is_expected.to have_body_text group_member.invite_token
+          end
+        end
+
+        context 'when there is an inviter' do
+          it 'contains all the useful information' do
+            is_expected.to have_subject "#{group_member.created_by.name} invited you to join GitLab"
+            is_expected.to have_body_text group.name
+            is_expected.to have_body_text group_member.human_access.downcase
+            is_expected.to have_body_text group_member.invite_token
+          end
+        end
+
+        it 'does add a param to the invite link' do
+          is_expected.to have_body_text 'new_user_invite'
+        end
+
+        it 'tracks an event' do
+          expect(Gitlab::Tracking).to receive(:event).with(
+            'Growth::Acquisition::Experiment::InviteEmail',
+            'sent',
+            property: 'experiment_group'
+          )
+
+          subject.deliver_now
+        end
       end
     end
 

spec/models/member_spec.rb

@@ -617,6 +617,24 @@ RSpec.describe Member do
     end
   end
 
+  describe "#invite_to_unknown_user?" do
+    subject { member.invite_to_unknown_user? }
+
+    let(:member) { create(:project_member, invite_email: "user@example.com", invite_token: '1234', user: user) }
+
+    context 'when user is nil' do
+      let(:user) { nil }
+
+      it { is_expected.to eq(true) }
+    end
+
+    context 'when user is set' do
+      let(:user) { build(:user) }
+
+      it { is_expected.to eq(false) }
+    end
+  end
+
   describe "destroying a record", :delete do
     it "refreshes user's authorized projects" do
       project = create(:project, :private)