Loopback 4 won't start after upgrading dependencies

[Bananenbrot1]

Dear loopback community,

I just upgraded my packages inside my project to the latest versions, after the upgrade the application wont start. When trying to debug, it always stops while running app.start().

I´m getting following error.

I tried setting up a new loopback application and it works inside there.

TypeError: Cannot set properties of undefined (setting 'application/json')
      at reduceSpecContent (node_modules/@loopback/openapi-v3/src/build-responses-from-metadata.ts:59:32)
      at Array.reduce (<anonymous>)
      at reduceSpecResponses (node_modules/@loopback/openapi-v3/src/build-responses-from-metadata.ts:78:49)
      at Array.reduce (<anonymous>)
      at buildResponsesFromMetadata (node_modules/@loopback/openapi-v3/src/build-responses-from-metadata.ts:149:57)
      at resolveControllerSpec (node_modules/@loopback/openapi-v3/src/controller-spec.ts:220:49)
      at getControllerSpec (node_modules/@loopback/openapi-v3/src/controller-spec.ts:531:12)
      at RestServer._createHttpHandler (node_modules/@loopback/rest/src/rest.server.ts:444:40)
      at RestServer._setupHandlerIfNeeded (node_modules/@loopback/rest/src/rest.server.ts:416:10)
      at RestServer.start (node_modules/@loopback/rest/src/rest.server.ts:975:10)
      at invokeTargetMethod (node_modules/@loopback/context/src/invocation.ts:263:47)
      at /Users/kirsche/Entwicklung/gutachter-backend/node_modules/@loopback/context/src/invocation.ts:240:12
      at transformValueOrPromise (node_modules/@loopback/context/src/value-promise.ts:298:12)
      at invokeTargetMethodWithInjection (node_modules/@loopback/context/src/invocation.ts:235:33)
      at invokeMethod (node_modules/@loopback/context/src/invocation.ts:181:14)
      at LifeCycleObserverRegistry.invokeObserver (node_modules/@loopback/core/src/lifecycle-registry.ts:193:25)
      at /Users/kirsche/Entwicklung/gutachter-backend/node_modules/@loopback/core/src/lifecycle-registry.ts:176:19
      at Array.map (<anonymous>)
      at LifeCycleObserverRegistry.notifyObservers (node_modules/@loopback/core/src/lifecycle-registry.ts:174:33)
      at LifeCycleObserverRegistry.notifyGroups (node_modules/@loopback/core/src/lifecycle-registry.ts:235:20)
      at processTicksAndRejections (node:internal/process/task_queues:96:5)
      at LifeCycleObserverRegistry.start (node_modules/@loopback/core/src/lifecycle-registry.ts:256:5)
      at GutachterBackendApplication.start (node_modules/@loopback/core/src/application.ts:365:5)
      at GutachterBackendApplication.start (node_modules/@loopback/boot/src/mixins/boot.mixin.ts:80:7)
      at setupApplication (src/__tests__/acceptance/test-helper.ts:36:3)
      at Context.<anonymous> (src/__tests__/acceptance/user.controller.acceptance.ts:17:22)

My application.ts

import {BootMixin} from '@loopback/boot';
import {ApplicationConfig} from '@loopback/core';
import {RepositoryMixin} from '@loopback/repository';
import {RestApplication} from '@loopback/rest';
import {RestExplorerBindings, RestExplorerComponent} from '@loopback/rest-explorer';
import {ServiceMixin} from '@loopback/service-proxy';
import * as dotenv from 'dotenv';
import * as dotenvExt from 'dotenv-extended';
import {AuthenticationComponent, Strategies} from 'loopback4-authentication';
import {AuthorizationBindings, AuthorizationComponent} from 'loopback4-authorization';
import multer from 'multer';
import path from 'path';
import {v4 as uuidv4} from 'uuid';
import {FILE_UPLOAD_SERVICE, STORAGE_DIRECTORY} from './keys';
import {BearerTokenVerifyProvider, ClientPasswordVerifyProvider, LocalPasswordVerifyProvider, ResourceOwnerVerifyProvider} from './modules/auth';
import {MySequence} from './sequence';

export {ApplicationConfig};

export class GutachterBackendApplication extends BootMixin(ServiceMixin(RepositoryMixin(RestApplication))) {
  constructor(options: ApplicationConfig = {}) {
    dotenv.config();
    dotenvExt.load({
      schema: '.env.example',
      errorOnMissing: false,
    });

    options.rest = options.rest || {};
    options.rest.port = +(process.env.PORT ?? 1337);
    options.rest.host = process.env.HOST;
    super(options);

    // Set up the custom sequence
    this.sequence(MySequence);

    // Set up default home page
    this.static('/', path.join(__dirname, '../public'));

    // Customize @loopback/rest-explorer configuration here
    this.configure(RestExplorerBindings.COMPONENT).to({
      path: '/explorer',
    });
    this.component(RestExplorerComponent);

    // Add authentication component
    this.component(AuthenticationComponent);
    // Customize authentication verify handlers
    this.bind(Strategies.Passport.OAUTH2_CLIENT_PASSWORD_VERIFIER).toProvider(ClientPasswordVerifyProvider);
    this.bind(Strategies.Passport.LOCAL_PASSWORD_VERIFIER).toProvider(LocalPasswordVerifyProvider);
    this.bind(Strategies.Passport.BEARER_TOKEN_VERIFIER).toProvider(BearerTokenVerifyProvider);
    this.bind(Strategies.Passport.RESOURCE_OWNER_PASSWORD_VERIFIER).toProvider(ResourceOwnerVerifyProvider);

    // Add authorization component
    this.bind(AuthorizationBindings.CONFIG).to({
      allowAlwaysPaths: ['/explorer'],
    });
    this.component(AuthorizationComponent);

    // Configure file upload with multer options
    this.configureFileUpload(options.fileStorageDirectory);

    this.projectRoot = __dirname;
    // Customize @loopback/boot Booter Conventions here
    this.bootOptions = {
      controllers: {
        // Customize ControllerBooter Conventions here
        dirs: ['controllers', 'modules'],
        extensions: ['.controller.js'],
        nested: true,
      },
      repositories: {
        dirs: ['repositories'],
        extensions: ['.repository.js'],
        nested: true,
      },
    };
  }

  /**
   * Configure `multer` options for file upload
   */
  protected configureFileUpload(destination?: string) {
    // Upload files to `dist/.sandbox` by default
    destination = destination ?? path.join(__dirname, '../temp');
    this.bind(STORAGE_DIRECTORY).to(destination);
    const multerOptions: multer.Options = {
      storage: multer.diskStorage({
        destination,
        // Use the original file name as is
        filename: (req, file, cb) => {
          cb(null, uuidv4() + '_' + file.originalname);
        },
      }),
    };
    // Configure the file upload service with multer options
    this.configure(FILE_UPLOAD_SERVICE).to(multerOptions);
  }
}

and my index.ts

import {ApplicationConfig, GutachterBackendApplication} from './application';

export * from './application';

export async function main(options: ApplicationConfig = {}) {
  const app = new GutachterBackendApplication(options);
  await app.boot();
  await app.start();

  const url = app.restServer.url;
  console.log(`Server is running at ${url}`);
  console.log(`Try ${url}/ping`);

  return app;
}

if (require.main === module) {
  // Run the application
  const config = {
    rest: {
      port: +(process.env.PORT ?? 3000),
      host: process.env.HOST,
      // The `gracePeriodForClose` provides a graceful close for http/https
      // servers with keep-alive clients. The default value is `Infinity`
      // (don't force-close). If you want to immediately destroy all sockets
      // upon stop, set its value to `0`.
      // See https://www.npmjs.com/package/stoppable
      gracePeriodForClose: 5000, // 5 seconds
      openApiSpec: {
        // useful when used with OpenAPI-to-GraphQL to locate your application
        setServersFromRequest: true,
      },
    },
  };
  main(config).catch(err => {
    console.error('Cannot start the application.', err);
    process.exit(1);
  });
}