Add reviewers detail to merge request unmergeable email

We currently have Assignee information only on text version so we'll
follow the same reasoning to be consistent.

app/mailers/previews/notify_preview.rb

@@ -92,6 +92,10 @@ class NotifyPreview < ActionMailer::Preview
     Notify.merge_request_status_email(user.id, merge_request.id, 'reopened', user.id).message
   end
 
+  def merge_request_unmergeable_email
+    Notify.merge_request_unmergeable_email(user.id, merge_request.id, 'conflict').message
+  end
+
   def merged_merge_request_email
     Notify.merged_merge_request_email(user.id, merge_request.id, user.id).message
   end

app/views/notify/merge_request_unmergeable_email.text.haml

@@ -6,3 +6,4 @@ Merge Request URL: #{project_merge_request_url(@merge_request.target_project, @m
 
 Author: #{sanitize_name(@merge_request.author_name)}
 = assignees_label(@merge_request)
+= reviewers_label(@merge_request)

changelogs/unreleased/300750-add-missing-reviewers-information-to-merge_request_unmergeable_ema.yml

+---
+title: Add reviewers detail to merge request unmergeable email
+merge_request: 55582
+author:
+type: added

spec/mailers/emails/merge_requests_spec.rb

@@ -24,6 +24,37 @@ RSpec.describe Emails::MergeRequests do
   let(:recipient) { assignee }
   let(:current_user_sanitized) { 'www_example_com' }
 
+  describe '#merge_request_unmergeable_email' do
+    subject { Notify.merge_request_unmergeable_email(recipient.id, merge_request.id) }
+
+    it_behaves_like 'an answer to an existing thread with reply-by-email enabled' do
+      let(:model) { merge_request }
+    end
+
+    it_behaves_like 'a multiple recipients email'
+    it_behaves_like 'it should show Gmail Actions View Merge request link'
+    it_behaves_like 'an unsubscribeable thread'
+    it_behaves_like 'appearance header and footer enabled'
+    it_behaves_like 'appearance header and footer not enabled'
+
+    it 'is sent as the merge request author' do
+      sender = subject.header[:from].addrs[0]
+      expect(sender.display_name).to eq(merge_request.author.name)
+      expect(sender.address).to eq(gitlab_sender)
+    end
+
+    it 'has the correct subject and body' do
+      aggregate_failures do
+        is_expected.to have_referable_subject(merge_request, reply: true)
+        is_expected.to have_body_text(project_merge_request_path(project, merge_request))
+        is_expected.to have_body_text('due to conflict.')
+        is_expected.to have_link(merge_request.to_reference, href: project_merge_request_url(merge_request.target_project, merge_request))
+        is_expected.to have_text_part_content(assignee.name)
+        is_expected.to have_text_part_content(reviewer.name)
+      end
+    end
+  end
+
   describe '#closed_merge_request_email' do
     subject { Notify.closed_merge_request_email(recipient.id, merge_request.id, current_user.id) }
 
@@ -131,13 +162,13 @@ RSpec.describe Emails::MergeRequests do
 
     it "has required details" do
       aggregate_failures do
-        expect(subject).to have_content title
-        expect(subject).to have_content merge_request.to_reference
-        expect(subject).to have_content current_user.name
-        expect(subject.html_part).to have_content(assignee.name)
-        expect(subject.text_part).to have_content(assignee.name)
-        expect(subject.html_part).to have_content(reviewer.name)
-        expect(subject.text_part).to have_content(reviewer.name)
+        is_expected.to have_content(title)
+        is_expected.to have_content(merge_request.to_reference)
+        is_expected.to have_content(current_user.name)
+        is_expected.to have_text_part_content(assignee.name)
+        is_expected.to have_html_part_content(assignee.name)
+        is_expected.to have_text_part_content(reviewer.name)
+        is_expected.to have_html_part_content(reviewer.name)
       end
     end
   end

spec/mailers/notify_spec.rb

@@ -464,44 +464,6 @@ RSpec.describe Notify do
         end
       end
 
-      describe 'that are unmergeable' do
-        let_it_be(:merge_request) do
-          create(:merge_request, :conflict,
-                 source_project: project,
-                 target_project: project,
-                 author: current_user,
-                 assignees: [assignee],
-                 description: 'Awesome description')
-        end
-
-        subject { described_class.merge_request_unmergeable_email(recipient.id, merge_request.id) }
-
-        it_behaves_like 'a multiple recipients email'
-        it_behaves_like 'an answer to an existing thread with reply-by-email enabled' do
-          let(:model) { merge_request }
-        end
-
-        it_behaves_like 'it should show Gmail Actions View Merge request link'
-        it_behaves_like 'an unsubscribeable thread'
-        it_behaves_like 'appearance header and footer enabled'
-        it_behaves_like 'appearance header and footer not enabled'
-
-        it 'is sent as the merge request author' do
-          sender = subject.header[:from].addrs[0]
-          expect(sender.display_name).to eq(merge_request.author.name)
-          expect(sender.address).to eq(gitlab_sender)
-        end
-
-        it 'has the correct subject and body' do
-          aggregate_failures do
-            is_expected.to have_referable_subject(merge_request, reply: true)
-            is_expected.to have_body_text(project_merge_request_path(project, merge_request))
-            is_expected.to have_body_text('due to conflict.')
-            is_expected.to have_link(merge_request.to_reference, href: project_merge_request_url(merge_request.target_project, merge_request))
-          end
-        end
-      end
-
       shared_examples 'a push to an existing merge request' do
         let(:push_user) { create(:user) }
 

spec/support/matchers/email_matcher.rb

+# frozen_string_literal: true
+
+RSpec::Matchers.define :have_text_part_content do |expected|
+  match do |actual|
+    @actual = actual.text_part.body.to_s
+    expect(@actual).to include(expected)
+  end
+
+  diffable
+end
+
+RSpec::Matchers.define :have_html_part_content do |expected|
+  match do |actual|
+    @actual = actual.html_part.body.to_s
+    expect(@actual).to include(expected)
+  end
+
+  diffable
+end