How to change the default error output in restify

Question

Is there any way that I can change the default error output? Say I'm going to change the rest error output:

{
    "code": "InvalidArgumentError",
    "message": "blah blah..."
}

to:

{
    "code": 10001,
    "message": "blah blah",
    "extraMsg": "blah blah"
}

Here are some of my ideas:

• Listen to the error events.
  It seems like not all the RestError have emitted extra events (like NotFound, MethodNotAllowed, VersionNotAllowed... do). So I can't catch all the errors to rewrite them.

• Listen to an event before response data sent.
  I look through the official documents and have found nothing relative.

• Modify the implementation of the RestError class.
  Well it's obviously not a good approach.

Any other ideas?

Jube

Answer 1

Finally I provide a customized JSON formatter to get what I want:

var server = restify.createServer( {
    formatters: {
        'application/json': function customizedFormatJSON( req, res, body ) {
            // Copied from restify/lib/formatters/json.js

            if ( body instanceof Error ) {
                // snoop for RestError or HttpError, but don't rely on
                // instanceof
                res.statusCode = body.statusCode || 500;

                if ( body.body ) {
                    body = {
                        code: 10001,
                        scode: body.body.code,
                        msg: body.body.message
                    };
                } else {
                    body = {
                        code: 10001,
                        msg: body.message
                    };
                }
            } else if ( Buffer.isBuffer( body ) ) {
                body = body.toString( 'base64' );
            }

            var data = JSON.stringify( body );
            res.setHeader( 'Content-Length', Buffer.byteLength( data ) );

            return data;
        }
    }
} );

Jube

Answer 2

While the answers above might work, the easiest way to add a custom field to the error body is to call the restify error constructor with an object (hash) instead of a string. The object has to contain the body key which is what you will see in the browser.

For example:

return next(new restify.InvalidArgumentError({body: {field: 'password', message: 'Password has to be at least 6 characters long'}}));

or

return next(new restify.UnauthorizedError({body: {foo: 'bar', name: 'john doe', message: 'whatever error message'}}));

Coranto

Answer 3

Restify offer many ways to implement error management : http://mcavage.github.io/node-restify/#Error-handling

Why don't you create a new error type "myError" just like sample code :

var restify = require('restify');
var util    = require('util');

function MyError(message) {
  restify.RestError.call(this, {
    restCode      : 'MyError',
    statusCode    : 418,
    message       : message,
    constructorOpt: MyError
  });  
  this.name = 'MyError';
}

util.inherits(MyError, restify.RestError);

For common errors I think that overloading methods is not such a bad idea... (I don't speak about modifying restify, just overloading functions using prototype)

(edited)

Fotinas

Extending RestError to create new Error Type will not help solve my problem. Maybe I'll try overloading functions using prototype.Thanks! – Jube

After a lot of research and some experience with restify I will give this a go as mangling with the formatters seems a bit much lifting. – Rostrum

Answer 4

I was able to provide additional data adding a property to the body object. Notice the this.body.errors = errors line

var restify = require('restify');
var util = require('util');

function ValidationError(message, errors) {
    restify.RestError.call(this, {
        restCode: 'ValidationError',
        statusCode: 400,
        message: message,
        constructorOpt: ValidationError
    });
    this.name = 'ValidationError';
    this.body.errors = errors; //<---
}

util.inherits(ValidationError, restify.RestError);
`

Crossgarnet

Answer 5

You can use restify-errors-options

Your example simply becomes:

const restify = require('restify');
const errors = require('restify-errors');
const errorsOptions = require('restify-errors-options');

errorsOptions.add('extraMsg');
const err = new errors.BadRequestError({extraMsg: 'whatever you want'});

err.toJSON();
//=> {code: 'BadRequest', message: '', extraMsg: 'whatever you want'}

Please also note that the solution provided was only tested on restify 5.x

Follow this issue for more information.

Octans