TypeError: Cannot use 'in' operator to search for 'promiseLibrary' in myproj

[denizdogan]

Do you want to request a feature or report a bug?

Bug

What is the current behavior?

/Users/deniz/Code/myproj/node_modules/mongoose/lib/connection.js:463
  if (!('promiseLibrary' in options)) {
                         ^

TypeError: Cannot use 'in' operator to search for 'promiseLibrary' in myproj
    at NativeConnection.Connection.openUri (/Users/deniz/Code/myproj/node_modules/mongoose/lib/connection.js:463:26)
    at Mongoose.createConnection (/Users/deniz/Code/myproj/node_modules/mongoose/lib/index.js:189:17)
    at Object.<anonymous> (/Users/deniz/Code/myproj/dist/index.js:19:36)
    at Module._compile (internal/modules/cjs/loader.js:689:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:700:10)
    at Module.load (internal/modules/cjs/loader.js:599:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:538:12)
    at Function.Module._load (internal/modules/cjs/loader.js:530:3)
    at Function.Module.runMain (internal/modules/cjs/loader.js:742:12)
    at startup (internal/bootstrap/node.js:236:19)
    at bootstrapNodeJSCore (internal/bootstrap/node.js:560:3)

If the current behavior is a bug, please provide the steps to reproduce.

import mongoose from 'mongoose'

const connection = mongoose.createConnection(
  process.env.MONGODB_HOST,
  process.env.MONGODB_DATABASE,
  process.env.MONGODB_PORT
)

export default connection

...or transpiled...

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;

var _mongoose = _interopRequireDefault(require("mongoose"));

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

var connection = _mongoose.default.createConnection(process.env.MONGODB_HOST, process.env.MONGODB_DATABASE, process.env.MONGODB_PORT);

var _default = connection;
exports.default = _default;

I've verified that the values in process.env are valid.

What is the expected behavior?

Expected is no error or better error message

Please mention your node.js, mongoose and MongoDB version.

• Node 10.6.0
• mongoose 5.2.4
• MongoDB 4.0.0

[lineus]

The parameter signature you are using with createConnection() is no longer valid as of mongoose 5, covered in the migration guide here.

I noticed that the mongoose 5 docs still have this specific signature in the api docs' createConnection example. I will put in a PR to remove this example momentarily.