feat(compartment-mapper): support treating top-level return in CJS as a way to export from module

[naugtur]

Description

One of the rarely used ways to export from a CJS module is to return a reference instead of setting module.exports to that reference. This PR adds support for that behavior and a tiny fixture in tests to ensure it works in all scenarios.

Security Considerations

N/A

Scaling Considerations

N/A

Documentation Considerations

It's part of CJS and also something very few people know. Documenting it would lead to more confusion than not.

Testing Considerations

Covered with a case in existing test coverage.

Compatibility Considerations

Increases ecosystem compatibility by the few unfortunate packages that use this way of exporting.

Upgrade Considerations

None

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Comments suppressed due to low confidence (3)

packages/compartment-mapper/src/parse-pre-cjs.js:51

• Ensure that the test suite includes scenarios where functor.call returns undefined, so that the fallback to module.exports is properly validated.

const returnValue = functor.call(

packages/compartment-mapper/src/parse-cjs.js:58

• Verify that tests cover cases when functor.call returns a defined value versus undefined, ensuring consistency in export behavior.

const returnValue = functor.call(

packages/compartment-mapper/src/parse-cjs-shared-export-wrapper.js:187

• Confirm that tests validate both branches of the conditional that selects returnValue or module.exports, ensuring that shared export logic behaves as expected.

const afterExecute = returnValue => {