fix: prevent double response in addAlbum when artistIdFromName throws

apps/backend/controllers/library.controller.ts

@@ -46,6 +46,7 @@ export const addAlbum: RequestHandler = async (req: Request<object, object, NewA
         console.error('Error: Failed to get artist_id from name');
         console.error(e);
         next(e);
+        return;
       }
     }
     if (!artist_id) {

tests/unit/controllers/library.addAlbum.test.ts

@@ -0,0 +1,40 @@
+import { jest } from '@jest/globals';
+
+jest.mock('../../../apps/backend/services/library.service', () => ({
+  artistIdFromName: jest.fn(),
+}));
+
+import { Request, Response, NextFunction } from 'express';
+import { addAlbum } from '../../../apps/backend/controllers/library.controller';
+import * as libraryService from '../../../apps/backend/services/library.service';
+
+function buildReqResNext(body: Record<string, unknown>) {
+  const req = { body } as unknown as Request;
+  const res = {
+    status: jest.fn().mockReturnThis(),
+    send: jest.fn().mockReturnThis(),
+    json: jest.fn().mockReturnThis(),
+  } as unknown as Response;
+  const next = jest.fn() as unknown as NextFunction;
+  return { req, res, next };
+}
+
+describe('addAlbum', () => {
+  it('should not send a response after calling next(e) when artistIdFromName throws', async () => {
+    const error = new Error('db connection lost');
+    (libraryService.artistIdFromName as jest.Mock).mockRejectedValue(error);
+
+    const { req, res, next } = buildReqResNext({
+      album_title: 'Test Album',
+      label: 'Test Label',
+      genre_id: 1,
+      format_id: 1,
+      artist_name: 'Test Artist',
+    });
+
+    await addAlbum(req, res, next);
+
+    expect(next).toHaveBeenCalledWith(error);
+    expect(res.send as jest.Mock).not.toHaveBeenCalled();
+  });
+});