Fix error when updating release with milestones

This commit fixes a bug that occured when attempting to update a
release that had at least one milestone associated. This was caused
by the UI incorrectly sending the entire milestone object to the API
instead of only sending the milestone title.

app/assets/javascripts/releases/util.js

@@ -15,13 +15,17 @@ import {
 export const releaseToApiJson = (release, createFrom = null) => {
   const name = release.name?.trim().length > 0 ? release.name.trim() : null;
 
+  // Milestones may be either a list of milestone objects OR just a list
+  // of milestone titles. The API requires only the titles be sent.
+  const milestones = (release.milestones || []).map(m => m.title || m);
+
   return convertObjectPropsToSnakeCase(
     {
       name,
       tagName: release.tagName,
       ref: createFrom,
       description: release.description,
-      milestones: release.milestones,
+      milestones,
       assets: release.assets,
     },
     { deep: true },

changelogs/unreleased/nfriend-fix-milestone-array-payload.yml

+---
+title: Fix error when updating releases with milestone associations through the UI
+merge_request: 47222
+author:
+type: fixed

spec/features/projects/releases/user_views_edit_release_spec.rb

@@ -4,7 +4,7 @@ require 'spec_helper'
 
 RSpec.describe 'User edits Release', :js do
   let_it_be(:project) { create(:project, :repository) }
-  let_it_be(:release) { create(:release, project: project, name: 'The first release' ) }
+  let_it_be(:release) { create(:release, :with_milestones, milestones_count: 1, project: project, name: 'The first release' ) }
   let_it_be(:user) { create(:user) }
 
   before do

spec/frontend/releases/util_spec.js

@@ -73,6 +73,18 @@ describe('releases/util.js', () => {
         expect(releaseToApiJson(release)).toMatchObject(expectedJson);
       });
     });
+
+    describe('when milestones contains full milestone objects', () => {
+      it('converts the milestone objects into titles', () => {
+        const release = {
+          milestones: [{ title: '13.2' }, { title: '13.3' }, '13.4'],
+        };
+
+        const expectedJson = { milestones: ['13.2', '13.3', '13.4'] };
+
+        expect(releaseToApiJson(release)).toMatchObject(expectedJson);
+      });
+    });
   });
 
   describe('apiJsonToRelease', () => {