middleware-chain | Chain your node.js middleware | Runtime Evironment library

As mentioned in formidable's README, "This is a low-level package". Therefore suitable for usage together with Node's http module.

You can't simply pass it as a express middleware, and the body parsing is done its own way.

Now, to the issues with your code:

1. express' "standard" body parser, body-parser, doesn't handle multipart requests. Therefore if you send anything else (urlencoded or JSON requests), express-validator will work fine.
2. You specified your validations before body parsing takes place. So when express-validator does its thing, it will see an empty req.body.
   Even if formidable worked out-of-box with express, according to your code it would be too late to validate anything.

As a side note, in my opinion a much better option in case you want to go a 100% express is multer.