Ideas for a v2

[dsnet]

Overall, this package has held up well. If we were to ever consider a v2, here are some changes:

• By default, always treat every variable as addressable, so that comparers and transformers that operate on a pointer can be used.
• Use generics where appropriate:

  package cmp
  func Comparer[T any](f func(T, T) bool) Option
  func FilterValues[T any](f func(T, T) bool) Option
  func Transformer[T, R any](name string, f func(T) R) Option

  package cmpopts
  func AcyclicTransformer[T, R any](name string, f func(T) R) Option
  func IgnoreFields[T any](names ...string) Option
  func IgnoreInterface[T any]() Option
  func IgnoreMapEntries[K comparable, V any](f func(K, V) bool) Option
  func IgnoreSliceElements[E any](f func(E) bool) Option
  func IgnoreType[T any]() Option
  func IgnoreUnexported[T any]() Option
  func SortMaps[K comparable](f func(K, K) bool) Option
  func SortSlices[T any](f func(T, T) bool) Option

  It's unclear whether SortMaps and SortSlices should take a less function (i.e., func(T, T) bool) or a compare function (i.e., func(T, T) int) to match the current slices.SortFunc signature.

[dprotaso]

It would be good if we could control whether the library panics or returns an error -

Knative has wrapped this library to handle that https://github.com/knative/pkg/blob/d0a82f9cbb8f2f92ce8f130c701f2da29bb33109/kmp/diff.go#L41

[Sung123zaaaa]

https://github.com/google/go-cmp/issues/338#issuecomment-1750773032

[zchee]

@dsnet v2 is roughly accepts backwards incompatible change. So would be happy if rename cmp package name to something (e.g., gocmp, or gcmp means Google Compare library...?) for conflicts stdlib cmp package.