Cannot find module '_isMockFunction'

[idahogurl]

Description

Starting with VS Code 1.74.1, I get the following error when running tests using Jest. It works with VS Code 1.73.1

 Cannot find module '_isMockFunction'
    Require stack:
    - /Users/Rebecca.Vest/dev/vs-code-prettier-eslint/.vscode-test/vscode-darwin-arm64-1.74.1/Visual Studio Code.app/Contents/Resources/app/out/bootstrap-amd.js
    - /Users/Rebecca.Vest/dev/vs-code-prettier-eslint/.vscode-test/vscode-darwin-arm64-1.74.1/Visual Studio Code.app/Contents/Resources/app/out/bootstrap-fork.js

Reproduction

1. Clone https://www.github.com/idahogurl/vs-code-prettier-eslint
2. Run yarn to install node modules
3. Run yarn test

This may be a VS Code issue.

[connor4312]

This is caused by Jest trying to check a property on every global. Which is questionable in a world where WeakSet exists. That is then triggers a proxy getter and causes this error.

@alexdima not sure if you want to do anything here

[JustinGrote]

@idahogurl downgrading to Jest 27.5.1 fixed this for me, I don't know specifically what version this got added in but a revert does fix it.

[rbuckton]

I put together a PR to work around this for jest: jestjs/jest#14188

I also have a workaround you can do locally. In your start.ts (or whatever script you point to with --extensionTestsPath), add the following lines to the top of the file:

declare global {
    var _VSCODE_NODE_MODULES: any;
}

if (globalThis._VSCODE_NODE_MODULES) {
    globalThis._VSCODE_NODE_MODULES = new Proxy(globalThis._VSCODE_NODE_MODULES, {
        get(target, p, receiver) {
            if (p === "_isMockFunction") return undefined;
            return Reflect.get(target, p, receiver);
        }
    });
}

This wraps the _VSCODE_NODE_MODULES proxy with one that simply returns undefined for _isMockFunction.

[jrieken]

Did this get fixed in jest or is this still an issue?

[vscodenpa]

This issue has been closed automatically because it needs more information and has not had recent activity. See also our issue reporting guidelines.

Happy Coding!