Honestly, for me it has worked pretty reliably outside of NixOS. I think there's a lot of false information on the internet, where people got stuck with a problem, then tried a bunch of different things without a structured process and somewhere in the middle they ran gralde clean and deleted all cashes. Then when they get unstuck they claim "cleaning and deleting all cashes will fix your problems", which is not the case most of the time.

In this particular case, I suspect that one of the jars from Gradle's native platform does something that doesn't work correctly on NixOS. Maybe it expects something to be in an FHS location, or something like that.

Right now, I don't know how we would fix this, because we can't install a fixed version of that jar into the cache, because we don't know the cache location beforehands.

ollijh has requested that we bump the default Gradle version to 9 as part of this PR, but to me this seems premature. I would think that the individual package maintainers should update individually and perhaps follow what the upstream packages are doing. And projects that use non-built-in plugins often need to wait for plugins to be updated.

I tried bumping three packages selected arbitrarily and none of them worked. See https://github.com/NixOS/nixpkgs/pull/421047#issuecomment-3189716199

Looks like there's been progress on removing gradle_7: https://github.com/NixOS/nixpkgs/issues/358845

(It looks like openjfx wasn't on the list. It looks like removing gradle_7 might mean no openjfx prior to 23, leaving only jfx 25 as a supported version. Apps can always pull the version of jfx they need from Maven Central, I suppose. I'm not sure how this will affect building JDKs with bundled jfx.)

But it sounds like (if I understand emily correctly) there is consensus here (in this room) that we can merge Gradle 9 without changing the default or making changes to any packages that use Gradle. This means initially that use of Gradle 9 will be opt-in.

And that we should remove Gradle 7 before 25.11, but Gradle 8 can remain the default for 25.11.

Is this a fair summary?

But it sounds like (if I understand emily correctly) there is consensus here (in this room) that we can merge Gradle 9 without changing the default or making changes to any packages that use Gradle. This means initially that use of Gradle 9 will (initially) be opt-in.

And that we should remove Gradle 7 before 25.11, but Gradle 8 can remain the default for 25.11.

Is this a fair summary?