SlackService - respect `notify_only_default_branch` for push events

app/models/project_services/chat_notification_service.rb

@@ -99,7 +99,7 @@ class ChatNotificationService < Service
   def get_message(object_kind, data)
     case object_kind
     when "push", "tag_push"
-      ChatMessage::PushMessage.new(data)
+      ChatMessage::PushMessage.new(data) if notify_for_ref?(data)
     when "issue"
       ChatMessage::IssueMessage.new(data) unless update?(data)
     when "merge_request"
@@ -145,10 +145,16 @@ class ChatNotificationService < Service
   end
 
   def notify_for_ref?(data)
-    return true if data[:object_attributes][:tag]
+    return true if data.dig(:object_attributes, :tag)
     return true unless notify_only_default_branch?
 
-    data[:object_attributes][:ref] == project.default_branch
+    ref = if data[:ref]
+            Gitlab::Git.ref_name(data[:ref])
+          else
+            data.dig(:object_attributes, :ref)
+          end
+
+    ref == project.default_branch
   end
 
   def notify_for_pipeline?(data)

changelogs/unreleased/33570-slack-notify-default-branch.yml

@@ -0,0 +1,5 @@
+---
+title: Fix Slack/Mattermost notifications not respecting `notify_only_default_branch` setting for pushes
+merge_request: 17345
+author:
+type: fixed

spec/support/slack_mattermost_notifications_shared_examples.rb

@@ -337,6 +337,7 @@ RSpec.shared_examples 'slack or mattermost notifications' do
 
         before do
           chat_service.notify_only_default_branch = true
+          WebMock.stub_request(:post, webhook_url)
         end
 
         it 'does not call the Slack/Mattermost API for pipeline events' do
@@ -345,6 +346,23 @@ RSpec.shared_examples 'slack or mattermost notifications' do
 
           expect(result).to be_falsy
         end
+
+        it 'does not notify push events if they are not for the default branch' do
+          ref = "#{Gitlab::Git::BRANCH_REF_PREFIX}test"
+          push_sample_data = Gitlab::DataBuilder::Push.build(project, user, nil, nil, ref, [])
+
+          chat_service.execute(push_sample_data)
+
+          expect(WebMock).not_to have_requested(:post, webhook_url)
+        end
+
+        it 'notifies about push events for the default branch' do
+          push_sample_data = Gitlab::DataBuilder::Push.build_sample(project, user)
+
+          chat_service.execute(push_sample_data)
+
+          expect(WebMock).to have_requested(:post, webhook_url).once
+        end
       end
 
       context 'when disabled' do