`formatError` error ignores custom error properties

[teckays]

I am throwing a custom error inside the resolver with additional parameters, unfortunately all custom fields are being stripped out from the formatError: error => {} callback.

// error 
class CustomError {
    constructor () {
        this.foo = 'bar'
    }
}

// resolver
try {
     throw new CustomError()
}

// graphQL
...
formatError: err => {
    console.log(err.foo) // undefined
}

[teckays]

Sorry, figured out that this is actually a bug in the graphql-js package

[teckays]

A "not very obvious err.originalError solution" found here: graphql/graphql-js#1192

[IvanGoncharov]

@teckays You don't need to replace formatError at all. If you do:

class CustomError {
    constructor () {
        this.extensions = { foo: 'bar' };
    }
}

It will be automatically exposed 🎉

[vnphanquang]

@teckays You don't need to replace formatError at all. If you do:

class CustomError {
    constructor () {
        this.extensions = { foo: 'bar' };
    }
}

It will be automatically exposed 🎉

I think this piece of information would be very helpful if added to the documentation (README). formatError is also helpful.