Merge pull request #64641 from sttts/sttts-ObjectConvertor-invariant

Automatic merge from submit-queue (batch tested with PRs 64641, 64532). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

apimachinery: adapt ObjectConvertor invariant

We avoid deepcopies in the codec/conversion stack by re-using data structures. This means that the out object of a conversion must be deepcopied before mutation in order to not mutate the in object as well.

This guarantees that e.g. runtime.Encode (which uses conversion from internal -> versioned) does not mutate the input. This would be highly unexpected (and we do not mention possible mutation of the input for runtime.Encode).
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@ -174,13 +174,16 @@ type ObjectVersioner interface {
// ObjectConvertor converts an object to a different version.
type ObjectConvertor interface {
// Convert attempts to convert one object into another, or returns an error. This method does
// not guarantee the in object is not mutated. The context argument will be passed to
// all nested conversions.
// Convert attempts to convert one object into another, or returns an error. This
// method does not mutate the in object, but the in and out object might share data structures,
// i.e. the out object cannot be mutated without mutating the in object as well.
// The context argument will be passed to all nested conversions.
Convert(in, out, context interface{}) error
// ConvertToVersion takes the provided object and converts it the provided version. This
// method does not guarantee that the in object is not mutated. This method is similar to
// Convert() but handles specific details of choosing the correct output version.
// method does not mutate the in object, but the in and out object might share data structures,
// i.e. the out object cannot be mutated without mutating the in object as well.
// This method is similar to Convert() but handles specific details of choosing the correct
// output version.
ConvertToVersion(in Object, gv GroupVersioner) (out Object, err error)
ConvertFieldLabel(version, kind, label, value string) (string, string, error)
}