Error while test extracting. Cannot convert object to primitive value

[X-Guardian]

Thanks for a great VSCode plugin.

I'm using the default evaluation-cjs extractWith option and not all of my tests are showing up in the VSCode test viewer. Looking at the Mocha Test Runner logs, I'm seeing lots of Error while test extracting Cannot convert object to primitive value messages.

I can re-create the issue with this simple test file:

import assert from 'assert';
import process from 'node:process';

const thisProcess = String(process);

describe('test1', function () {
    it('should be true', function () {
        assert.equal(true, true);
    });
});

which produces the following error when refreshing the test list in VSCode:

Error while test extracting  Cannot convert object to primitive value /mocha-test/src/test1/test1.spec.ts:25
const thisProcess = String(import_node_process.default);
                    ^

TypeError: Cannot convert object to primitive value

Any thoughts?

[Danielku15]

Hey there. Seems this problem started with some changes in ECMAScript2026.
I already narrowed down the problem and I'm working on a fix 😉

The cause is (if it's interesting):

In the evaluation-cjs mode all imports are mocked to avoid unexpected side-effects. assert and process are actually a Proxy object during test discovery, same for all members.

With ECMAScript2026 the String constructor accesses the Symbol.toPrimitive of the passed object. And the extension is violating the contract of ES2026:

The language does not enforce alignment between the hint and the result type, although Symbol.toPrimitive must return a primitive, or a TypeError is thrown. (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/toPrimitive)

As we return again a proxy from toPrimitive the seen error appears.

[X-Guardian]

Great to hear you were already aware of the issue @Danielku15. I'll await the fix with anticipation.

[Danielku15]

Fix is already merged and available in 1.3.2 😉 you should be able to upgrade already

[X-Guardian]

Thanks @Danielku15. Just updated in VSCode to v1.3.2 and all the test extraction errors are gone!

In the OpenVSX Marketplace (used by Cursor), the latest version is 1.3.0. Can you update it here too?

[Danielku15]

It likely took a bit longer until it made it through the verification but it was deployed along the VS Code Marketplace and is available by now:

https://open-vsx.org/extension/coderline/mocha-vscode/1.3.2