JSON stringified error does not contain message

[Jokero]

In my app I use res.status(err.status).send(err) to send error. send uses JSON.stringify for objects. Stringified error does not contain message.

Example:

var createError = require('http-errors');

var error  = createError(404, 'message', { description: 'description' });
var error2 = createError(404, { message: 'message', description: 'description' });

console.log(JSON.stringify(error));  // {"description":"description"}
console.log(JSON.stringify(error2)); // {"description":"description"}

[dougwilson]

As far as I know, this is the way JavaScript itself works (try running JSON.stringify(new Error('oops!'))). If you would like to fix this, please feel free to make a PR :)

[dougwilson]

@Jokero any interest in making a PR for this?

[Jokero]

I want to make a PR in the future to completely update this module. https://github.com/Jokero/http-error/blob/master/index.js

[dougwilson]

Ok, @Jokero , though this module's interface is part of Koa, so any major changes please make sure you discuss with the Koa project first.

[jonathanong]

i'm 👍 to making everything stringify-able, particularly err.message and err.code (i think it was code that couldn't be stringified...)

here's of an example of us hacking around it: https://github.com/stream-utils/raw-body/blob/1e45346682da648ab02e5c92577de10caab905ac/index.js#L167

i don't see how this would break backwards incompatibility, but we could just add it to koa v2

[Jokero]

@jonathanong As workaround I created separate npm module https://github.com/Jokero/http-error-constructor

Every property instead of statusCode, status and name is stringified. I excluded statusCode and status because you can always get it from response without any additional field in error body.

It's possible to create error with custom status code (there is http-errors issue for it). I use real constructors instead of error factories, so additionally you can do like this:

var err = new HttpError.BadRequest();
console.log(err instanceof HttpError);            // true
console.log(err instanceof HttpError.BadRequest); // true

It fixes another issue.

[dougwilson]

@jonathanong what do you think if we just added a toJSON method to the root prototype that would understand how to serialize all the properties (especially the non-own properties like statusCode)? It could potentially implement the .expose logic in the serialization, but not sure if that's a good idea or not.