VM ESM with dynamic imports resolves promises before linking is complete

• Version: v14.1.0
• Platform: Darwin Simens-MacBook-Pro.local 18.7.0 Darwin Kernel Version 18.7.0: Mon Feb 10 21:08:45 PST 2020; root:xnu-4903.278.28~1/RELEASE_X86_64 x86_64
• Subsystem: VM, ESM

What steps will reproduce the bug?

See https://github.com/SimenB/node-vm-esm-promise-awaiting

Run node --experimental-vm-modules index.js to reproduce.

How often does it reproduce? Is there a required condition?

Almost every time. There seems to be some race condition in there. I've added a manual timeout in there - tweak its numbers to see different behavior. In the code the timeout is 1 second and then one of the tests fail almost every time. Increasing the timeoyt will often make both tests fail

What is the expected behavior?

All linking and execution should happen before the promises resolve.

What do you see instead?

The promises resolve, so the internal state of completed is set to true, which later throws.

Additional information

The reproduction is adapted from a bug report to Jest (https://github.com/facebook/jest/issues/9430#issuecomment-622664754), so apologies if it looks a little wonky. I've tried to emulate sorta what happens under the hood in Jest down to solely node core modules.

Note that I might very well have gotten some semantics wrong in the dynamic linking, so please tell me if I'm doing something really dumb in the reproduction (except having no module cache at all) - I've probably made the same mistake in Jest's implementation. Main difference is that the calls will linger - In jest these would all be inside test() calls or some such that we execute later. I don't think it impacts the reproduction much though - the promises resolve seconds before linking complete, so I don't think it's necessarily tied to dangling promises. I might very well be wrong though.

For some extra context if it's helpful, here's Jest's implementation: https://github.com/facebook/jest/blob/7a3c9977847cc9fafed6f6662289f3c35e44e0c6/packages/jest-runtime/src/index.ts#L323-L456

It's spread a bit around, but those are the essential bits where we use the VM APIs.

Start with index.js in the linked reproduction and run node --experimental-vm-modules index.js on the reported VM/ESM scenario. Trace when the promises resolve relative to linking and execution; the issue is done when linking and execution consistently complete before those promises resolve.