acklen-keystone/admin/server/middleware/apiError.js

Web Application Framework and Admin GUI / Content Management System built on Express.js and Mongoose

var assign = require('object-assign');

/*
	This middleware simplifies returning errors from the API.

	Example usage patterns and expected responses:
		apiError('database error', err) => 500 { err }
		apiError(403, 'invalid csrf') => 403 { error: 'invalid csrf' }
		apiError(403, 'validation errors', err) => 403 { error: 'validation errors', detail: err }
		apiError(403, 'not allowed', 'You can not delete yourself') => 403 { error: 'not allowed', detail: 'You can not delete yourself' }
		apiError(400, err) => 400 { err }
		apiError(err) => 500 { err }
*/

module.exports = function (req, res, next) {
	res.apiError = function apiError (statusCode, error, detail) {
		// process arguments
		if (typeof statusCode !== 'number' && detail === undefined) {
			detail = error;
			error = statusCode;
			statusCode = 500;
		}
		// apply the status code
		if (statusCode) {
			res.status(statusCode);
		}
		// unpack { error, detail } objects passed as the error argument w/o detail argument
		if (!detail && typeof error === 'object'
			&& error.toString() === '[object Object]'
			&& error.error && error.detail)
		{
			detail = error.detail;
			error = error.error;
		}
		// turn Errors into useful output
		if (error instanceof Error) {
			error = error.name !== 'Error' ? error.name + ': ' + error.message : error.message;
		}
		if (detail instanceof Error) {
			detail = detail.name !== 'Error' ? detail.name + ': ' + detail.message : detail.message;
		}
		// send error as json
		var data = typeof error === 'string' || (error && detail)
			? { error: error, detail: detail }
			: error;
		res.json(data);
		return assign({
			statusCode: statusCode,
		}, data);
	};
	next();
};