New Hash methods in Ruby 2.5 and hash-polyfill

Ruby 2.5 includes a bunch of new Hash methods:

• Hash#slice
• Hash#transform_keys
• Hash#transform_keys!

The first two do exactly what you'd expect them - and the same ActiveSupport's methods with the same names do. In case of key conflict Hash#transform_keys will quietly overwrite keys, which is somewhat questionable behaviour, but it's not like there's obvious better way.

Unfortunately Hash#transform_keys! took some shortcuts, resulting in rather questionable behaviour. I submitted it as a bug report, and hope they fix it soon, but to be honest track record of my Open Source bug submissions is rather poor.

I'm really surprised Hash#compact wasn't included.

If you want to use these new methods in older Ruby versions, or if you want to use methods from future rubies like Hash#compact, Hash#select_values, Hash#select_keys etc., I updated hash-polyfill gem too.

I did not include Hash#transform_keys! in the gem as its unclear if it will have corrected or current questionable behaviour long term.