Remove invalid uniqueItems property from CRDs when Sets are used

[sbernauer]

Motivation

This fixes the error message Forbidden: uniqueItems cannot be set to true since the runtime complexity becomes quadratic in case a HashSet (or similar) is used.

Solution

Don't write the field uniqueItems.
Ideally we could set x-kubernetes-list-type instead, but I'm not really comfortable making this change as I'm not so deep into this topic.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.4%. Comparing base (6d0c9b1) to head (e90ae39).

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #1484     +/-   ##
=======================================
+ Coverage   74.4%   74.4%   +0.1%     
=======================================
  Files         78      78             
  Lines       6775    6778      +3     
=======================================
+ Hits        5034    5037      +3     
  Misses      1741    1741             

Files	Coverage Δ
kube-core/src/schema.rs	90.0% <100.0%> (+0.3%)	⬆️
kube-derive/tests/crd_schema_test.rs	96.9% <100.0%> (+0.2%)	⬆️

... and 1 file with indirect coverage changes

[clux]

Thanks for reporting this. I think the fix makes sense. Unsure of whether it makes sense to feature gate it to above Kubernetes 1.30 via k8s_if_le_1_30 but that requires k8s-openapi to actually release an 1.30 one first.

[sbernauer]

Sorry for force-pushing, as always I forgot to sign my commits...

Maybe my "As of version 1.30 Kubernetes does not support [...]" comment was a bit misleading.
I got the error on both 1.27 and 1.29, I just added the current latest version 1.30 for future readers as the behavior might be changed in a future k8s version. Happy to remove it as it can cause confusion.

With that in mind would a feature gate still make sense here?

[clux]

This makes sense to me. Thanks!

[clux]

A feature gate might make sense, but that would mean we wait to include this until we can gate on 1.30 (so basically bump openapi, merge this with a gate, then release next kube). 🤔

[clux]

Do you have a source for the removal of uniqueItems support?

[sbernauer]

I still can't wrap my head around the whole feature gate thing.

They earliest occurrence of this error message I could find is from 2017: kubernetes/kubernetes@fd09c3d
Since then (and probably forever) uniqueItems can not be set to true.

[clux]

Ah, then I don't think we don't need to feature gate it imo as it's always been considered invalid (even if it hasn't been promoted to a hard error until recently). If people care about it then they can fix it properly with the override, and they will actually see the effects of this immediately with our change here (by us changing the CRD output slightly) so it should be more helpful to get this immediately than to wait for 1.30.

[sbernauer]

even if it hasn't been promoted to a hard error until recently

Ah that was the part I was missing. Thanks for the clarification!