Enum breaks ts-jest

[bodinsamuel]

May be related to #944 #962

Issue

I struggled to find a good reason why ts-jest was failing. I first thought my aliases were the source of it. But I reproduced the bug, and finally understood. Accessing an ENUM value is breaking ts-jest.

const a = MyEnum['value'];

It throws:

Cannot find module '../types/tet' from
However, Jest was able to find:

Expected behavior

Well, working obviously 🥺
I found many old issues talking about enum, but nothing in the doc mentioning that specifically.
There is a mention of const enum which is not exactly my case here. And passing isolatedModules to false or true does not change the outcome.

Minimal repo

Here is the smallest repo possible, with all explanation in it (install and run basically)
https://github.com/bodinsamuel/ts-jest-not-working-with-enum/tree/master

[projekt86]

Downgrading to <23.10.0 works for me

[ahnpnl]

hi @bodinsamuel , I've checked your repo. You have tet.d.ts but you don't have tet.ts which causes the error. If you put your enum into tet.ts it will work. d.ts extension is type definition file, I wouldn't put enum definition into d.ts to avoid issues. I will close this issue as it's working.

[ahnpnl]

Please see the detail of explanation here

[ncuillery]

@ahnpnl thanks for the explanation, but what are we supposed to do if the enum is defined in a 3rd-party d.ts file? like https://github.com/software-mansion/react-native-gesture-handler/blob/master/react-native-gesture-handler.d.ts
Duplicate it? 😕

[ahnpnl]

Hi, I think you can ask jest to skip d.ts from transforming. If jest doesn’t give d.ts to ts-jest, typescript compiler api in ts-jest internal wont throw errors. In general, the input files ts-jest processes depending on jest, whatever jest gives, ts-jest will process.

[ncuillery]

Oh sorry I was unclear. My use-case is the following:

I'm using this enum from the react-native-gesture-handler definition file: react-native-gesture-handler.d.ts#L32-L39

So in my code, in the file I'd like to test, I have:

import { [....], State } from "react-native-gesture-handler";

[....]

if (state === State.BEGAN) {

[....]

And my test fails on TypeError: Cannot read property 'BEGAN' of undefined. But I have no control on the State enum. The d.ts is needed, the enum is defined in it.

The best workaround I could find is to mock the State enum in the jest setup file with a plain old JavaScript object:

jest.mock("react-native-gesture-handler", () => ({
  PanGestureHandler: () => "PanGestureHandler",
  NativeViewGestureHandler: () => "NativeViewGestureHandler",
  State: {
    UNDETERMINED: 0,
    FAILED: 1,
    BEGAN: 2,
    CANCELLED: 3,
    ACTIVE: 4,
    END: 5
  }
}));

[ahnpnl]

I don't have any other ways other than your provided workaround :( but I think your workaround looks good. Thanks for sharing. In general, d.ts should be generated from a ts file, that will make it easier to use when distributing a package via npm.