Verify function and properly throwing an error?

[RayDeanTech]

The .json(), .raw(), .text(), and .urlencoded() parsers each have their own verify(req, res, buf, encoding) function.

What is the intention of the verify function? Is it primarily used for "whole body" validation? (Like, confirming req.body is a valid JSON object or parse-able XML doc, etc... ?)

The JSON example below is pretty sexy, but I'm having trouble throwing an error properly for the XML example:

Trying to validate that req.body is a parse-able XML document... but can't quite figure out how to properly throw an error:

     const xml2js = require('xml2js');
     const xmlParser = xml2js.Parser();

    verify: (req, res, buf, encoding) => {
            console.log(`text parser, body encoding: ${encoding}`)

            xmlParser.parseString(req.body, (err, result) => {
                if (err) {
                    console.log(err)
                    res.status(400).send(err);
                    throw Error(err);
                } else {
                    console.log(result)
                    return true;
                }
            })



    }

Here's a pretty sweet (working) example of throwing an error if the req.body is invalid JSON (don't know where I stole this from). This does not crash my application.

app.use(express.json({
	verify: (req, res, buf, encoding) => {
		try {
			JSON.parse(buf);
		} catch (e) {
			res.status(400).send(e.message);
			throw Error('invalid JSON');
		}
	}
}));

[dougwilson]

The verify argument is called before the body has been parsed and is meant to be used to abort prior to parsing by throwing an error. The purpose of the option is for body signature valudation.

[krzysdz]

An example would be verification of requests received on webhook like when using Messenger Platform API (example from Facebook: https://github.com/fbsamples/messenger-platform-samples/blob/f7558fe2b0f21b8e5d25a5a18472ccd140f8628c/node/app.js#L145-L173, verifyRequestSignature is passed as verify in the line 24).

[RayDeanTech]

Ok... I think in my case I'm going to just do the XML validation stuff somewhere in my controller.

The ability to do the JSON buffer thingy inside that verify function is super-cool IMHO. XML is such a pain.

Thank you!!!!!! :)