express-validator can not validate while using multer

whenever I submit my form with empty values the express-validator works fine and sends the validation errors, however when I also submit the form with NOT EMPTY VALUES I get errors too, I’m really confused about what’s wrong with this code?

const {check, validationResult} = require('express-validator');
var multer = require('multer');
var upload = multer({dest: 'uploads/'});

router.post(
    '/add',
    [
        check('title', 'title field is required').not().isEmpty(),
        check('text', 'text field is required').not().isEmpty()
    ],
    upload.single('mainImage'),
    (req, res) =>{

        const validationErrors = validationResult(req);

        if(!validationErrors.isEmpty()){
            // in every situation, only this part of code is going to be executed
            return res.status(422).json({errors: validationErrors.array()});
        }else{
            // inserting into DB
            res.send();
        }
});

[nico-sorice]

@Alirezaies

Hi, i know its a little bit late, but since this is one of the first search results for this issue, one way to do it’s using “checkSchema” to check for basically anything in the request object.

You can do something like this:

const multer = require('multer');

const upload = multer({
    limits: {fileSize: 10 * Math.pow(1024, 2 /* MBs*/)},
    fileFilter(req, file, cb){
        //Validate the files as you wish, this is just an example
        cb(null, file.mimetype === 'application/pdf');
    },
});

const {check, checkSchema, validationResult} = require('express-validator');

app.post('/test', [
    upload.fields([
        {name: 'resume_file', maxCount: 1},
        {name: 'another_file', maxCount: 3},
    ]),
    check('email', 'Email field is invalid, etc etc').not().isEmpty().isEmail().isLength({max: 255}),
    checkSchema({
        'resume_file': {
            custom: {
                options: (value, { req, path }) => !!req.files[path],
                errorMessage: 'You should upload a PDF file up to 10Mb',
            },
        },
        'another_file': {
            custom: {
                options: (value, { req, path }) => !!req.files[path] && req.files[path].length >= 2,
                errorMessage: 'You should upload at least two PDF files, up to 10Mb',
            },
        },
    }),
    (req, res, next) => {
        const errors = validationResult(req);

        if(!errors.isEmpty()){
            return res.status(422).json({
                message: 'Request fields or files are invalid, but im handling all of them together!',
                errors: errors.array(),
            })
        }

        //Your route logic, knowing that both the fields, and the files are valid

        return res.status(200).json({
            message: 'Request fields and files are valid!',
        })
    }
]);

And now you can have all your errors messages handled by express-validator, while the file will only be uploaded if it is a valid file acording to your multer fileFilter.

Bear in mind that if you’re using multer.only(field), etc, you will have to change the custom options in the validator accordingly, since .only will make the only file available at req.file, instead of at req.file[path].

[Alirezaies]

by using upload.single('mainImage') before the check(), no validation error will be produced by express-validator, but if I put the upload.single('mainImage') after the check() I get validation errors on both empty and filled form.

StackOverflow didn’t help at all