File upload middleware does not work when I chain it with other middlewares. I get req.file = undefined

Author: imhazard17Created Mar 23, 2024Updated Mar 27, 2026

Labelsquestionrequires-triage

When I try to upload file without chaining the middlewares, the file upload works but when I chain it with other middlewares like input validation and authentication the file does not upload and I get req.file/req.files object as undefined.

Kindly help me to find what the issue is as I have been not able to find one yet.

I use postman to test the api and have set the correct body, authorization token and form data but still the error persists.

Github link of the project: https://github.com/imhazard17/user_mvp

Endpoint

// PUT /upl/upload
router.put('/upload', [userInputValidation, authentication, upload.single('file')], errForward(async (req, res) => {
    if (!req.file) {
        return res.status(404).json({ err: 'File not uploaded' })
    }

    return res.status(200).json({ file: req.file })
}))

Authentication middleware

function authentication(req, res, next) {
    if(!req.headers.authorization) {
        return res.status(411).json({
            err: 'Could not find auth token'
        })
    }

    const authToken = req.headers.authorization.split(' ')[1]

    let jwtVerifyRes
    
    try {
        jwtVerifyRes = jwt.verify(authToken, process.env.JWT_SECRET)
    } catch(e) {
        return res.status(403).json({
            err: 'Could not authenticate user'
        })
    } finally {
        req.locals = {}
        req.locals.userId = parseInt(jwtVerifyRes)
        next()
    }
}

Input validation middleware

function userInputValidation(req, res, next) {
    const schema = z.object({
        username: z.string().min(5).max(30)
        password: z.string().min(8).max(40),
        firstName: z.string().max(30).optional(),
        lastName: z.string().max(30).optional(),
    })

    try {
        schema.parse(req.body)
    } catch(e) {
        return res.status(411).json({
            err: 'Wrong inputs recieved'
        })
    } finally {
        next()
    }
}

Source: expressjs/multer

View original on GitHub View discussion on GitHub