javascript - NodeJS Bluebird promise 在处理程序中创建但未从中返回

Question

我有以下 nodejs 代码作为快速中间件功能

Middleware.is_authenticated = function(req, res, next)
{
    if(req.system_session == undefined || req.system_session.login_status == false) return res.status(401).send({errors: true, error: 'invalid_session', session: req.system_session}).end();

    Session.validate_session(req.system_session, req.ip, req.headers['user-agent'])

    .then(function(session)
    {
        return next();
    })

    .catch(function(err)
    {
        req.system_session.destroy();
        return res.status(401).send({errors: true, error: err.message, session: req.system_session}).end();
    });
};

我的 Session.validate_session 代码:

Session.validate_session = function(user, user_ip, user_agent)
{
    return new Promise(function(resolve, reject)
    {
        if(user.user_id == null || user.user_name == null || user.user_rank == null || user.user_session == null || user_ip == null || user_agent == null) return reject(new Error('invalid_session'));

        new api_session({user_session: user.user_session}).fetch({columns: ['user_id', 'user_name', 'user_rank', 'user_session', 'user_ip', 'user_agent']})

        .then(function(result)
        {
            if(result == null) return reject(new Error('invalid_session'));

            return result.toJSON();
        })

        .then(function(session)
        {
            if(session == null || session.user_id != user.user_id || session.user_name != user.user_name || session.user_rank != user.user_rank || session.user_ip != user_ip || session.user_agent != user_agent) return reject(new Error('invalid_session'));

            return resolve(session);
        })

        .catch(function(err)
        {
            return reject(err);
        });
    });
};

一切都在正常工作，一切都在数据库中完美执行，以及解析“下一个”路由，甚至显示响应。但无论我尝试什么，我总是得到“在处理程序中创建了一个 promise ，但没有从它返回”

Warning: a promise was created in a handler at middleware.js:12:11 but was not returned from it

at new Promise (/Users/Bill/Documents/app/node_modules/bluebird/js/release/promise.js:77:14)
at Object.Permission.permission_list (/Users/Bill/Documents/app/app/security/permission.js:8:10)
at PermissionService.permission_list (/Users/Bill/Documents/app/app/http/services/permission_service.js:6:14)
at Layer.handle [as handle_request] (/Users/Bill/Documents/app/node_modules/express/lib/router/layer.js:95:5)
at next (/Users/Bill/Documents/app/node_modules/express/lib/router/route.js:131:13)
at /Users/Bill/Documents/app/app/http/middleware.js:12:11
at processImmediate [as _immediateCallback] (timers.js:383:17)

From previous event:
at Middleware.is_authenticated (/Users/Bill/Documents/app/app/http/middleware.js:10:4)
at Layer.handle [as handle_request] (/Users/Bill/Documents/app/node_modules/express/lib/router/layer.js:95:5)
at next (/Users/Bill/Documents/app/node_modules/express/lib/router/route.js:131:13)
at Route.dispatch (/Users/Bill/Documents/app/node_modules/express/lib/router/route.js:112:3)
at Layer.handle [as handle_request] (/Users/Bill/Documents/app/node_modules/express/lib/router/layer.js:95:5)
at /Users/Bill/Documents/app/node_modules/express/lib/router/index.js:277:22
at Function.process_params (/Users/Bill/Documents/app/node_modules/express/lib/router/index.js:330:12)
at next (/Users/Bill/Documents/app/node_modules/express/lib/router/index.js:271:10)
at clientSession (/Users/Bill/Documents/app/node_modules/client-sessions/lib/client-sessions.js:630:5)
at Layer.handle [as handle_request] (/Users/Bill/Documents/app/node_modules/express/lib/router/layer.js:95:5)
at trim_prefix (/Users/Bill/Documents/app/node_modules/express/lib/router/index.js:312:13)
at /Users/Bill/Documents/app/node_modules/express/lib/router/index.js:280:7
at Function.process_params (/Users/Bill/Documents/app/node_modules/express/lib/router/index.js:330:12)
at next (/Users/Bill/Documents/app/node_modules/express/lib/router/index.js:271:10)
at SendStream.error (/Users/Bill/Documents/app/node_modules/express/node_modules/serve-static/index.js:121:7)
at emitOne (events.js:77:13)
at SendStream.emit (events.js:169:7)
at SendStream.error (/Users/Bill/Documents/app/node_modules/express/node_modules/send/index.js:275:17)
at SendStream.onStatError (/Users/Bill/Documents/app/node_modules/express/node_modules/send/index.js:392:12)

如果有人有任何解决方案那就太好了。我在我的项目中有很多 promise ，它们都非常相似，而且都运行良好，但我就是无法理解这个。

Answer 1

这来自基于 promise 的代码 (Session.validate_session) 与基于回调的代码 (next) 的混合。预计 next() 调用不是异步的(不创建任何 promise )或者返回那个 promise ，但它没有(blame express) .

有两种方法可以避免警告:

• 让 express 进行错误处理，并在发生错误时调用 next。在这种情况下，您可以使用 .asCallback method :

  Middleware.is_authenticated = function(req, res, next) {
      if (req.system_session == undefined || req.system_session.login_status == false)
          var promise = Promise.reject(new Error('invalid_session'));
      else
          var promise = Session.validate_session(req.system_session, req.ip, req.headers['user-agent']);
  
      promise.asCallback(next);
  };
  

• 作为warning explanation说，你可以显式地返回null而不是返回next()产生的undefined值:

  Middleware.is_authenticated = function(req, res, next) {
      if (req.system_session == undefined || req.system_session.login_status == false)
          var promise = Promise.reject(new Error('invalid_session'));
      else
          var promise = Session.validate_session(req.system_session, req.ip, req.headers['user-agent'])
          .catch(function(err) {
              req.system_session.destroy();
              throw err;
          });
  
      promise.then(function(session) {
          next();
          return null;
      }, function(err) {
          res.status(401).send({errors: true, error: err.message, session: req.system_session}).end();
      });
  };