Support jest esm mode

[viceice]

Feature Request

Description:

I'm using jest in esm mode, because my code simply requires it. But i can't use this library as it expects jest globals.

Possible solution:

Import jest from @jest/globals . https://jestjs.io/docs/ecmascript-modules#differences-between-esm-and-commonjs

• ref #408

[SimenB]

where does jest-extended use jest? it should only use expect, which is still a global (unless you've disabled it)

[viceice]

ok, it's disabled 🙃

but I've also type issues after enable. So if i add 'jest-extended' to my tsconfig.json , it also makes all jest types global again and vscode no longer suggests to import them, which of caus will fail when running tests (at least the jest global isn't available)

[SimenB]

right. if you disable the globals you'll need to extend yourself.

import {expect} from '@jest/globals';
import jestExtendedMatchers from 'jest-extended';

expect.extend(jestExtendedMatchers);

we can probably expose some /all-imported thing which does this. Wanna send a PR?

(some discussion in #333)

[Alexsey]

@SimenB unfortunately, what you suggest is not working because import from jest-extended gives this error:

TS2306: File '/Users/aleksey/Code/DOS-liquidation-bot/node_modules/jest-extended/types/index.d.ts' is not a module.

After spending quite a lot of time and trying everything from docs and issues, I didn't find a single workaround - there is just no way jest-extended can be used with ESM and TypeScript :(

[SimenB]

Does adding export {} at the bottom of that file work?

[Alexsey]

Thank you for the quick reply! It removed the error but types on expect(...) didn't appear

The issue is only with types - adding "setupFilesAfterEnv": ["jest-extended/all"] to jest config itself making the code with @ts-expect-error/@ts-ignore on jest-extended method calls work

UPD: Of course, I have "types": ["node", "jest", "jest-extended"] in compilerOptions of tsconfig. But considering that types is about globals and auto-imports, it shouldn't matter, because with ESM I'm forced to use explicitly imported expect

[johncrim]

I'm having the same issue - was not able to get jest-extended to work in jest using ESM. @Alexsey - did you ever find a solution?

I tried a while back and gave up...

[Alexsey]

Unfortunately, not

[mvshmakov]

For the reference, @testing-library/jest-dom coped with it in the following way: https://github.com/testing-library/jest-dom/issues/426

[Alexsey]

Update for jest-extended v4.0.0:

• the error on import from 'jest-extended' has been fixed
• return value of expect(...) is still missing the jest-extended types

For example expect([]).toBeArray() will give the error:

TS2339: Property 'toBeArray' does not exist on type 'Matchers  & SnapshotMatchers  & Inverse  > & PromiseMatchers '.

[Peeja]

It sort of looks like index.d.ts is trying to merge its matchers into the Expect interface, but instead it's just creating a new local Expect interface.

[Alexsey]

@Peeja this is a TypeScript feature called declaration merging that allows extending the Expect, even though jest-extended code doesn't own it, by redeclaring it. Of course, Expect is expected to be in global scope, otherwise a dummy local Expect interface would be created

[Peeja]

@Alexsey Yes, I know. That's exactly the point I'm making.

[nlwillia]

This hacky import and a declaration workaround seems to work for matchers at least.

import {expect} from '@jest/globals'
expect.extend((await import('jest-extended')).default)

declare module '@jest/expect' {
    export interface Matchers<R extends void | Promise<void>> extends CustomMatchers<R> {}
}

For asymmetric matchers, expect can't be declaration merged because it's a type, but it can be casted. ex: (expect as any).toSatisfy(...)

    "@types/jest": "29.5.9",
    "jest": "29.7.0",
    "jest-extended": "4.0.2",
    "ts-jest": "29.1.1",
    "typescript": "5.3.2"