Process emails for projects with not unique service desk keys

Prevent errors with emails sent to projects
with not unique service desk keys.

Changelog: fixed
MR: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/62139

app/models/project.rb

@@ -636,6 +636,12 @@ class Project < ApplicationRecord
   scope :with_tracing_enabled, -> { joins(:tracing_setting) }
   scope :with_enabled_error_tracking, -> { joins(:error_tracking_setting).where(project_error_tracking_settings: { enabled: true }) }
 
+  scope :with_service_desk_key, -> (key) do
+    # project_key is not indexed for now
+    # see https://gitlab.com/gitlab-org/gitlab/-/merge_requests/24063#note_282435524 for details
+    joins(:service_desk_setting).where('service_desk_settings.project_key' => key)
+  end
+
   enum auto_cancel_pending_pipelines: { disabled: 0, enabled: 1 }
 
   chronic_duration_attr :build_timeout_human_readable, :build_timeout,
@@ -837,12 +843,6 @@ class Project < ApplicationRecord
 
       from_union([with_issues_enabled, with_merge_requests_enabled]).select(:id)
     end
-
-    def find_by_service_desk_project_key(key)
-      # project_key is not indexed for now
-      # see https://gitlab.com/gitlab-org/gitlab/-/merge_requests/24063#note_282435524 for details
-      joins(:service_desk_setting).find_by('service_desk_settings.project_key' => key)
-    end
   end
 
   def initialize(attributes = nil)

lib/gitlab/email/handler/service_desk_handler.rb

@@ -65,10 +65,9 @@ module Gitlab
         def project_from_key
           return unless match = service_desk_key.match(PROJECT_KEY_PATTERN)
 
-          project = Project.find_by_service_desk_project_key(match[:key])
-          return unless valid_project_key?(project, match[:slug])
-
-          project
+          Project.with_service_desk_key(match[:key]).find do |project|
+            valid_project_key?(project, match[:slug])
+          end
         end
 
         def valid_project_key?(project, slug)

spec/lib/gitlab/email/handler/service_desk_handler_spec.rb

@@ -168,7 +168,7 @@ RSpec.describe Gitlab::Email::Handler::ServiceDeskHandler do
       end
 
       context 'when using service desk key' do
-        let_it_be(:service_desk_settings) { create(:service_desk_setting, project: project, project_key: 'mykey') }
+        let_it_be(:service_desk_key) { 'mykey' }
         let(:email_raw) { service_desk_fixture('emails/service_desk_custom_address.eml') }
         let(:receiver) { Gitlab::Email::ServiceDeskReceiver.new(email_raw) }
 
@@ -176,6 +176,10 @@ RSpec.describe Gitlab::Email::Handler::ServiceDeskHandler do
           stub_service_desk_email_setting(enabled: true, address: 'support+%{key}@example.com')
         end
 
+        before_all do
+          create(:service_desk_setting, project: project, project_key: service_desk_key)
+        end
+
         it_behaves_like 'a new issue request'
 
         context 'when there is no project with the key' do
@@ -193,6 +197,20 @@ RSpec.describe Gitlab::Email::Handler::ServiceDeskHandler do
             expect { receiver.execute }.to raise_error(Gitlab::Email::ProjectNotFound)
           end
         end
+
+        context 'when there are multiple projects with same key' do
+          let_it_be(:project_with_same_key) { create(:project, group: group, service_desk_enabled: true) }
+          let(:email_raw) { service_desk_fixture('emails/service_desk_custom_address.eml', slug: project_with_same_key.full_path_slug.to_s) }
+
+          before do
+            create(:service_desk_setting, project: project_with_same_key, project_key: service_desk_key)
+          end
+
+          it 'process email for project with matching slug' do
+            expect { receiver.execute }.to change { Issue.count }.by(1)
+            expect(Issue.last.project).to eq(project_with_same_key)
+          end
+        end
       end
     end
 

spec/models/project_spec.rb

@@ -1584,19 +1584,20 @@ RSpec.describe Project, factory_default: :keep do
     end
   end
 
-  describe '.find_by_service_desk_project_key' do
-    it 'returns the correct project' do
+  describe '.with_service_desk_key' do
+    it 'returns projects with given key' do
       project1 = create(:project)
       project2 = create(:project)
       create(:service_desk_setting, project: project1, project_key: 'key1')
-      create(:service_desk_setting, project: project2, project_key: 'key2')
+      create(:service_desk_setting, project: project2, project_key: 'key1')
+      create(:service_desk_setting, project_key: 'key2')
+      create(:service_desk_setting)
 
-      expect(Project.find_by_service_desk_project_key('key1')).to eq(project1)
-      expect(Project.find_by_service_desk_project_key('key2')).to eq(project2)
+      expect(Project.with_service_desk_key('key1')).to contain_exactly(project1, project2)
     end
 
-    it 'returns nil if there is no project with the key' do
-      expect(Project.find_by_service_desk_project_key('some_key')).to be_nil
+    it 'returns empty if there is no project with the key' do
+      expect(Project.with_service_desk_key('key1')).to be_empty
     end
   end