Node.js – v20.8.0

That's linking to a performance issue, but the nodejs fixes were about memory leaks and use-after-free.

So it sounds like different issues.

There is already a PR on the way to fix the performance regression with what Jest s doing https://github.com/nodejs/node/pull/49950

Note we also ship a test runner ourselves pretty recently and it may suit your needs.

It's definitely unsettling when we don't fully understand why a fix works. I suppose one could argue that, in that sense, software development is as much art as it is science... you learn and adapt, and over time, the understanding of why certain fixes work may become clearer. I wish I could remember the specific instances of this throughout my career, but I remember at least a few where we were happy to have the fix (even though it was annoying we didn't understand the why) and then months or more later we came to fully understand why. I distinctly remember how, in many of these cases, it felt to us like it would've impossible to even come close to the why without first just having the fix. That's what made it even more frustrating — that we felt we needed to understand the underlying issue in order to fix it but then it felt like there's no way we would've understood what the underlying issue was without the fix! In that way, it kind of all just felt like luck or a miracle...which is definitely not very confidence-inspiring.

Is this for the ESM custom loaders?

I haven’t touched module loader hooks for a while, but my impression is that the changes bring it more conceptually in line with require hooks. Loader authors will likely provide the register call for end users (to load with --import, roughly analogous to loading require hooks with --require?), so you won’t need to call anything in an extra step unless you’re authoring a loader yourself. In which case this provides for composition patterns which the earlier CLI-only entry (mostly) didn’t.

We have at least ±5 more changes on the way to improve streams significantly (Node streams, then web streams), reduce the size of each stream and hot-path common cases.