Metadata is removed with std.record.filter

[dgengtek]

Hello,

std.record.filter removes all metadata. Is this intended?

nickel> let i = {zone | doc "dns zone" = "A", records | Array String | doc "dns records" | priority -1 = []}
nickel> i
{
  records | Array String | doc "dns records" | priority -1 = [  ],
  zone | doc "dns zone" = "A",
}

nickel> std.record.filter (fun k v => k != "zone") i
{ records = [  ], }

nickel-lang-cli nickel 1.15.1 (rev 806e740)

[yannham]

It's indeed a surprising behavior. It's not surprising when looking at the implementation, which is the composition of std.record.to_array, std.record.filter and std.record.from_array, but I agree that this probably not what you expect as a user. Whether it freezes the record or not (see std.record.freeze), it should probably keep the metadata.

Fixing this is going to a bit annoying, as we'll either need a specialized primop or a way to manipulate metadata from pure Nickel code, but I think it should be fixed anyway.