Fix for https://github.com/samselikoff/ember-cli-mirage/issues/1386

mirage.js

import Response from "ember-cli-mirage/response";
import RouteHandler from "ember-cli-mirage/route-handler";
import FunctionHandler from "ember-cli-mirage/route-handlers/function";
import { MirageError } from "ember-cli-mirage/assert";

// Workaround for https://github.com/samselikoff/ember-cli-mirage/issues/1386
RouteHandler.prototype._getMirageResponseForRequest = function (request) {
  let result;
  try {
    /*
        We need to do this for the #serialize convenience method. Probably is
        a better way.
      */
    if (this.handler instanceof FunctionHandler) {
      this.handler.setRequest(request);
    }

    result = this.handler.handle(request);
  } catch(e) {
    if (e instanceof MirageError) {
      throw e;
    } else {
      console.error(`Mirage ${request.method} handler for the url ${request.url} threw an error:\n\n${e.stack || e}`); // eslint-disable-line no-console

      result = new Response(500, {}, e.message || e);
    }
  }

  return this._toMirageResponse(result);
};