Thanks for contributing!

I think several of these are very similar to existing combinators. In particular:

• fromEitherM(v) <-> v.absolve
• ofEither(v, ifLeft) <-> fromEither(v).mapError(ifLeft)
• ofEitherM(v, ifLeft) <-> v.flatMap(fromEither(_).mapError(ifLeft))
• ofOption(v, ifEmpty) <-> fromOption(v).orElseFail(ifEmpty)
• ofOptionM(v, ifEmpty) <-> v.someOrFail(ifEmpty)

I think most of these are pretty straightforward and at most take two method calls when you essentially want to do two things: lifting a value into an effect an transform the error value. The one that is not quite as nice is the replacement for your ofEitherM method. rightOrFail almost does what we need but not quite because it just lets us specify a new error value and not transform the existing error value. Maybe we add a rightOrFailWith variant for that?

@Fristi Are you interested in working on the leftOrFailWith and rightOrFailWith variants?

Yes, let's see if I can squeeze some time on it this week

Sounds good. Let me know if there is anything I can do to help.

I added those combinators and some helpful documentation I think :) Let me know what you think

Great! Looking forward to have it in the next release

@Fristi Thanks for your contribution on this!