esm: fix esm load bug

[ZYSzys]

If module.reflect is undefined, just run into else condition.

Fixes: #25482

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

[guybedford]

Unfortunately we can't just override the module map - it has to be treated as an immutable map otherwise we can possibly get race conditions in loading / different instances.

The fix here has to be to ensure the onReady function is available as soon as the moduleMap entry is set.

[guybedford]

(or change the architecture to not need an onReady)

[ZYSzys]

So how should this to be fixed specifically ？Can you please give me some more guides ?

I've changed it like we previously did: https://github.com/nodejs/node/pull/24560/files#diff-76195ce57689942222a27f0dbda6d3b7L641

Sincerely /cc @devsnek who actual implement the refactor in #24560 (comment)

[devsnek]

lite ci run to see if this fix passes https://ci.nodejs.org/job/node-test-pull-request-lite-pipeline/2243/

[guybedford]

One thing to try might be checking if reflect is available once module.modulePromise has resolved. It would be good to get a test case that captures what is happening in #25482 as well.

Thanks @ZYSzys for your efforts here.

[devsnek]

the current change passes all tests, so maybe we're on to something?

cc @bmeck for some hopeful insight

[guybedford]

So the problem here is that the CJS cache injects into the ESM loader so they share the same instances, but in the case where the ESM loader has already loaded the module, the CJS version should not override the existing ESM version.

So the fix is correct.

I've merged the test case from #27443 into this PR, and can confirm it is fully resolved.

Please lets land this soon and backport the patch as well.

[Trott]

LGTM, but I'd prefer we cherry-pick or am in the test to preserve authorship for the contributor who wrote it, unless there's a good reason not to do that.

[ZYSzys]

@Trott I've cherry-pick the test and will squash the last fixup when landed, is it ok now ?

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/23083/

[guybedford]

Thanks @ZYSzys for updating that - of course we should retain the original commit.

[ZYSzys]

Landed in 523a9fb...ac3b98c

@aduh95 Thanks and congratulate for your first(Oh, it's not your first time 😅, but still congratulate) contribution to Node.js core 🎉.