Nodejs imap-simple UnhandledPromiseRejectionWarning issue

Question

I'm currently using the nodejs package imap-simple to check an email is sent.

I've copied and pasted the relevant code from the imap-simple site to firstly delete existing emails.

The code is as follows;

 
var config = {
    imap: {
        user: '[email protected]',
        password: 'yourpassword',
        host: 'imap.gmail.com',
        port: 993,
        tls: true,
        authTimeout: 3000
    }
};
imaps.connect(config).then(function (connection) {        
    connection.openBox('INBOX').then(function () {
    
        var searchCriteria = ['ALL'];
        var fetchOptions = { bodies: ['TEXT'], struct: true };
        return connection.search(searchCriteria, fetchOptions);
 
    //Loop over each message
    }).then(function (messages) {
        let taskList = messages.map(function (message) {
            return new Promise((res, rej) => {
                var parts = imaps.getParts(message.attributes.struct); 
                parts.map(function (part) {
                    return connection.getPartData(message, part)
                    .then(function (partData) {
                        
                        //Display e-mail body
                        if (part.disposition == null && part.encoding != "base64"){
                            console.log(partData);
                        }
 
                        //Mark message for deletion
                        connection.addFlags(message.attributes.uid, "\Deleted", (err) => {
                            if (err){
                                console.log('Problem marking message for deletion');
                                rej(err);
                            }
 
                            res(); //Final resolve
                        })
                    });
                });
            });    
        })
 
        return Promise.all(taskList).then(() => {
            connection.imap.closeBox(true, (err) => { //Pass in false to avoid delete-flagged messages being removed
                if (err){
                    console.log(err);
                }
            });
            connection.end();
        });
    });
});

However, it appears to be failing and when it fails the following error is recorded;

(node:8063) UnhandledPromiseRejectionWarning: Error: read ECONNRESET at TCP.onStreamRead (internal/stream_base_commons.js:111:27) (node:8063) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1) (node:8063) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

I'm not really sure why this unhandled error is being created (as the code has been pasted from the imap-simple site - apart from the user credentials of course).

I've read elsewhere that I probably need to add a catch somewhere, but I've never used promises before so some guidance as to where I need to add these catch commands within the imap-simple code would be greatly appreciated.

TheFloppyToast TheFloppyToast · Accepted Answer · 2020-09-09T10:52:39

If the connection to the imap server itself failes, then you might want to check your config and authentication. In any case to catch the errors you can use the following:

imaps.connect(config).then(function (connection) {  
    ....
})
.then(....)
.catch((e) => {}) //handle error here

Since you are using .then() you can simply chain a .catch() as you would a .then(). This works if you have multiple .then() chained as well, however for your nested async calls you might want to add another .catch() in the same way.

Nodejs imap-simple UnhandledPromiseRejectionWarning issue

1 Answers