Propose Try.toEither(Throwable => L)

[eslep]

Thank You

Thank you for all of the work on Vavr! It has quickly become my favorite Java library, and usually the first thing I add to every new project ❤️ Aside from the benefit to my own code, it has also been a great tool to help teach others about FP and get them curious about it.

Proposal / What is this?

I come across cases where I want to convert a Try to an Either while mapping the Failure value onto a Left value. One example would be safely handling code which isn't mine, then mapping the Throwable onto an error type.

I do this normally either with fold(throwableMapper, identity()) or .toEither().mapLeft(throwableMapper), but find that .toEither(throwableMapper) would be a nice shortcut to replace either case. I have also a few colleagues who would appreciate the addition from a readability standpoint I think, so I thought I'd suggest it.

Implementation

By my own style, I'd normally just write this as a wrapper around a fold call. However, as a first contribution, I am trying to stick as close as possible to the style I already see in the code here.

By that reasoning, the code style, namings, and Javadoc are all created based on examples I find existing within the file.

Since the toEither(Supplier) implementation assumes the Supplier is pure/will not throw an exception and does not handle such a case, I have followed the same assumption here as well.