habitica/website/src/middlewares/api-v3/errorHandler.js

'use strict';

// The error handler middleware that handles all errors 
// and respond to the client

let errors = require('../../libs/api-v3/errors');
let CustomError = errors.CustomError;
let InternalServerError = errors.InternalServerError;

module.exports = function (err, req, res, next) {
  // TODO add logging
  
  // In case of a CustomError class, use it's data
  // Otherwise try to identify the type of error (mongoose validation, mongodb unique, ...)
  // If we can't identify it, respond with a generic 500 error

  let responseErr = err instanceof CustomError ? err : null;

  if (!responseErr) {
    // Try to identify the error...
    // ...
    // Otherwise create an InternalServerError and use it
    // we don't want to leak anything, just a generic error message
    responseErr = new InternalServerError();
  }

  return res
    .status(responseErr.httpCode)
    .json({
      error: responseErr.name,
      message: responseErr.message
    });
};