javascript - Bluebird 无法拒绝错误的问题。解决就好了。错误使应用程序崩溃

Question

我正在处理 app使用 node-imap ，而且我一直在处理错误或缺少错误时遇到了困难。我有以下功能:

////imap-helpers.js
function searchBox(searchTerm, bodies){
  return new Promise(function(resolve, reject){
    searchTerm = searchTerm || ['ALL']
    bodies = bodies || ['HEADER.FIELDS (FROM TO CC BCC SUBJECT)','TEXT']
    imap.search(searchTerm, function(err, results){
      if (err) reject(err)
      var messages = [], newMessage = {}, count=0;
      var f = imap.fetch(results, {
        bodies: bodies,
        struct: true
      });

      f.on('message', function(msg) {
        newMessage = {}

        msg.on('body', function(stream, info) {
          //When we get a message, append the header to header, text to body.
          stream.on('data', function(chunk){
            if (info.which !== 'TEXT')
              newMessage.rawHeader += chunk.toString('utf8')
            else
              newMessage.body += chunk.toString('utf8')
          })

          //When stream is done, strip the unparsable characters at the beginning before parsing.
          //NOTE: I'm not actually sure what these unparseable characters actually are
          //but this all works kosher.
          stream.once('end', function() {
            if (info.which !== 'TEXT'){
              newMessage.rawHeader = newMessage.rawHeader.replace(/^undefined/, '')
              newMessage.header = Imap.parseHeader(newMessage.rawHeader)
            }
            if(newMessage.body)
              newMessage.body = newMessage.body.replace(/^undefined/, '')
          })
        })

        msg.once('attributes', function(attrs) {
          newMessage.attrs = attrs
        })

        msg.once('end', function() {
          messages[count] = _.omit(newMessage, 'rawHeader')
          count++
        })

      })

      f.on('error', function(e){
        reject(e)
      })

      f.once('end', function(){
        resolve(messages)
      })

    })
  })
}

exports.getByUID = function(boxName, uid){
  boxName = boxName || 'INBOX'
  var searchTerm = ['ALL',['UID',uid]]
  return imap.openBoxAsync(boxName, false).then(function(){
    return searchBox(searchTerm, ['HEADER.FIELDS (FROM TO CC BCC SUBJECT)']).then(function(messages){
      return messages
    }).catch(function(e){
      throw e
    })
  }).catch(function(e){
    return e
  })
}

然后我可以在文件中调用它。

//imap-controller.js - severely amended version
  getOne: function(req, res){
    methods.getByUID('INBOX',req.params.uid).then(function(response){
      res.json(response)
    }).catch(function(e){
      res.json({error: e.message})
    })
  }

但问题是我没有运气将错误返回给 Controller 。它只是不断地打破程序

Unhandled rejection Error: Nothing to fetch
    at Connection._fetch (/Users/dkranec/github/imap/node_modules/imap/lib/Connection.js:778:11)
    at Connection.fetch (/Users/dkranec/github/imap/node_modules/imap/lib/Connection.js:771:15)
    at Connection.tryCatcher (/Users/dkranec/github/imap/node_modules/bluebird/js/main/util.js:26:23)
    at Connection.ret [as fetchAsync] (eval at <anonymous> (/Users/dkranec/github/imap/node_modules/bluebird/js/main/promisify.js:163:12), <anonymous>:15:23)
    at /Users/dkranec/github/imap/app.js:34:12
    at tryCatcher (/Users/dkranec/github/imap/node_modules/bluebird/js/main/util.js:26:23)
    at Promise._settlePromiseFromHandler (/Users/dkranec/github/imap/node_modules/bluebird/js/main/promise.js:503:31)
    at Promise._settlePromiseAt (/Users/dkranec/github/imap/node_modules/bluebird/js/main/promise.js:577:18)
    at Promise._settlePromises (/Users/dkranec/github/imap/node_modules/bluebird/js/main/promise.js:693:14)
    at Async._drainQueue (/Users/dkranec/github/imap/node_modules/bluebird/js/main/async.js:123:16)
    at Async._drainQueues (/Users/dkranec/github/imap/node_modules/bluebird/js/main/async.js:133:10)
    at Immediate.Async.drainQueues [as _onImmediate] (/Users/dkranec/github/imap/node_modules/bluebird/js/main/async.js:15:14)
    at processImmediate [as _immediateCallback] (timers.js:371:17)

请在此处查看我在此主题上发表的相关 reddit 帖子，其中包含此功能的小版本，作为我制作的应用程序，如果您认为您可以帮助解决此问题，我也会遇到问题 here .基本上是同一问题的另一个版本，但会捕获错误但不会在成功时发出 imap.fetch 发射器。我赢不了!

Answer 1

在 searchBox()主要要做的是return;在 reject(err); 之后，正如@KirillSlatin 在上面的评论中所说。

这是整个功能以及一些进一步(未经测试)的建议:

function searchBox(searchTerm, bodies) {
    return new Promise(function(resolve, reject) {
        searchTerm = searchTerm || ['ALL'];
        imap.search(searchTerm, function(err, results) {
            if (err) {
                reject(err);
                return; // <<<<<<<<<<<<<<<<<<< 
            }
            var messages = [],
                f = imap.fetch(results, {
                    bodies: bodies || ['HEADER.FIELDS (FROM TO CC BCC SUBJECT)','TEXT'],
                    struct: true
                });
            f.on('message', function(msg) {
                var rawHeader = '',
                    newMessage = { body: '' };
                msg.on('body', function(stream, info) {
                    stream.on('data', function(chunk) { ((info.which == 'TEXT') ? newMessage.body : rawHeader) += chunk.toString('utf8') });
                    // stream.once('end', function() { });//no point doing anything here providing msg.once('end') fires later.
                });
                msg.once('attributes', function(attrs) { newMessage.attrs = attrs; });
                msg.once('end', function() {
                    newMessage.header = rawHeader.length ? Imap.parseHeader(rawHeader) : '';
                    newMessage.attrs = newMessage.attrs || [];//safety
                    messages.push(newMessage);
                });
            });
            f.on('error', reject);
            f.once('end', function() { resolve(messages); });
        });
    });
}

与 newMessage在 f.on('message') 中声明处理程序，当嵌套事件发生时，无论事件调度的性质如何 - 同步或异步，都没有消息串扰的机会。

和 .getByUID()将传递任何错误而无需捕获/重新抛出:

exports.getByUID = function(boxName, uid) {
    return imap.openBoxAsync(boxName || 'INBOX', false).then(function() {
        return searchBox(['ALL', ['UID', uid]], ['HEADER.FIELDS (FROM TO CC BCC SUBJECT)']);
    });
}