Realm-js: Jest tests with jest.resetModules() fails after upgrade to 2.2.4

[jerdie]

Goals

update to [email protected]

Expected Results

Successful test

Actual Results

got error from test with realm imported

    TypeError: Cannot redefine property: Worker
        at Function.defineProperty (native)

    > 1 | import Realm from 'realm';

Steps to Reproduce

1. install realm2.2.4
2.

import Realm from 'realm';
describe("Testing realm", () => {
    beforeEach(() => {
        jest.resetModules();
    });
    test("realm", () => {
        const realm2 = require('realm')
    })
})

1. run test

Version of Realm and Tooling

• Realm JS SDK Version: 2.2.4
• Node or React Native: React native jest
• Client OS & Version: Windows
• Which debugger for React Native: None

Adding configurable: true in realm/lib/index.js's Object.defineProperty(realmConstructor fixes the issue.
Not sure if this is a bug. Can you provide a workaround?

[jerdie]

Update:

I noticed that this happens on tests that have mocks. Error occurs when the test has import, do a jest.resetModules() or jest.resetAllMocks() and then do a require('realm').

[kneth]

I can easily imagine that mocking can lead to troubles. A Realm object is not a plain JavaScript object as the object is managed by Realm and not the JS engine.

We have to investigate a bit further and I label it as a bug for now.

Thanks for the report and the suggested fix.

[jdelafon]

Edit: Same problem with Realm 2.2.1 and 2.2.6.
Edit: Deleting and re-cloning my project solved the problem
Edit: Deleting ".realm.lock", ".realm.management", ".realm.note" does not solve it.

Error occurs when the test has import, do a jest.resetModules() or jest.resetAllMocks() and then do a require('realm').

Sorry but I don't understand what the workaround is.

I import Realm in a service that I want to test, I cannot just require('realm') in each one of my tests.

I am not using Jest mocks, but I get the same error on all test suites involving Realm.

It happens randomly, too, while adding code and without changing any lib version. I reverted my work to a commit where the tests did pass, but now they do not anymore. Any cache to reset maybe (I tried jest --clearCache) ?

[jerdie]

Still haven't found a workaround for this. I just stated how to replicate it in my last comment. Once i get the error, all of my test that has a module that imports realm also gets the error. I'm stuck using "realm": "~2.1.1".

[benweidig]

Running into the same issue, some of my services import Realm directly so jest.resetModules() isn't fixing it 100% for me

[kneth]

I would like to know if anyone have tried to upgrade to 2.2.14?

[jerdie]

@kneth
Still having the same error for test in description in 2.2.14.

``` FAIL __tests__TestRealm.js
● Testing realm › realm

TypeError: Cannot redefine property: Worker
    at Function.defineProperty (native)

   5 |     });
   6 |     test("realm", () => {
>  7 |         const realm2 = require('realm')
   8 |     })
   9 | })

"dependencies": {
"react": "16.0.0",
"react-native": "0.51.0",
"realm": "^2.2.14"
},
```

[alexbassy]

I too get this Cannot redefine property: Worker error message. 😓

The tests run fine the first time, then when they're rerun (with --watch), I get that message. I've tried all the workarounds in this thread:

• jest.resetModules() and jest.resetAllMocks() in beforeEach and reassigning the variable to require('realm')
• delete the repo and start again (worth a shot)
• upgrade to latest versions of realm and jest (2.2.14 and 22.4.2 respectively)
• I tried passing in the Realm import from the test file, and using the provided in my class

Now I will downgrading to an older version of Realm to see if that works

Edit:

Here is a quick gist I made that reproduces the problem. Tests pass the first time, but second time round:

Edit again:

I searched for Worker in the realm module, and changing this line in node_modules/realm/lib/index.js:125 fixes my problem 🎉

Object.defineProperty(realmConstructor, 'Worker', {value: nodeRequire('./worker')});

// to

if (!realmConstructor.Worker) {
    Object.defineProperty(realmConstructor, 'Worker', {value: nodeRequire('./worker')});
}

I'm new to Realm and I don't use the "Sync" option at all, so I'm not sure if this causes a problem or not. This seems more like a symptom of a problem than the cause, so I'll hold off creating a PR 😛

[kneth]

I close the issue as #1695 has been merged and released as part of 2.2.15.

[weijiederrick91]

hi may i ask if any workaround for the above problem cause i keep on have
Test suite failed to run

TypeError: Cannot redefine property: Worker
    at Function.defineProperty (<anonymous>)

  1 | 'use strict'
  2 | 
> 3 | import Realm from 'realm';
  4 | import { getModelList } from './DatabaseModel';
  5 | import {log} from '../../Log'
  6 | export const File = 'DatabaseService'

  at Object.<anonymous> (node_modules/realm/lib/index.js:125:14)
  at Object.<anonymous> (src/lib/managers/mgrDatabase/DatabaseService.js:3:12)
  at Object.<anonymous> (src/lib/managers/mgrResource.js:135:71)

[max-konin]

Hi. After update to 2.2.15:

TypeError: Cannot redefine property: Permissions
        at Function.defineProperty (<anonymous>)

[kneth]

I have merged #1723 but we need to backport it to the 2.2.x series (branch 2.2.x).