Don't include changes in webhook payload when old associations are empty

Signed-off-by: Rémy Coutable <remy@rymai.me>

app/models/concerns/issuable.rb

@@ -411,8 +411,8 @@ module Issuable
     changes = previous_changes
 
     if old_associations
-      old_labels = old_associations.fetch(:labels, [])
-      old_assignees = old_associations.fetch(:assignees, [])
+      old_labels = old_associations.fetch(:labels, labels)
+      old_assignees = old_associations.fetch(:assignees, assignees)
 
       if old_labels != labels
         changes[:labels] = [old_labels.map(&:hook_attrs), labels.map(&:hook_attrs)]
@@ -423,7 +423,7 @@ module Issuable
       end
 
       if self.respond_to?(:total_time_spent)
-        old_total_time_spent = old_associations.fetch(:total_time_spent, nil)
+        old_total_time_spent = old_associations.fetch(:total_time_spent, total_time_spent)
 
         if old_total_time_spent != total_time_spent
           changes[:total_time_spent] = [old_total_time_spent, total_time_spent]

changelogs/unreleased/dont-include-changes-in-webhook-payload-when-old-associations-is-empty.yml

+---
+title: Don't include changes in webhook payload when old associations are empty
+merge_request: 35158
+author:
+type: fixed

spec/models/concerns/issuable_spec.rb

@@ -416,6 +416,27 @@ RSpec.describe Issuable do
   describe '#to_hook_data' do
     let(:builder) { double }
 
+    context 'when old_associations is empty' do
+      let(:label) { create(:label) }
+
+      before do
+        issue.update!(labels: [label])
+        issue.assignees << user
+        issue.spend_time(duration: 2, user_id: user.id, spent_at: Time.current)
+        expect(Gitlab::HookData::IssuableBuilder)
+          .to receive(:new).with(issue).and_return(builder)
+      end
+
+      it 'delegates to Gitlab::HookData::IssuableBuilder#build and does not set labels, assignees, nor total_time_spent' do
+        expect(builder).to receive(:build).with(
+          user: user,
+          changes: {})
+
+        # In some cases, old_associations is empty, e.g. on a close event
+        issue.to_hook_data(user)
+      end
+    end
+
     context 'labels are updated' do
       let(:labels) { create_list(:label, 2) }