In v2, allow a way to convert from document.source index to Position

[itsmeknt]

Hello! I have a feature request for v2.

Background:
TextDocument.offset_at_position(), already implemented here, is a nice way to get the character index of document.source given the client's types.Position struct.

Request:
It would be nice to also have the reverse lookup. Given the character indexes of document.source, I would like a way to decode that into types.Position so that I easily specify in the response, for example, which text the inline completion will replace.

I couldn't find a way to do this by looking through the source code, so I implemented a hacky solution.

I also noticed the jedi-language-server application created their own approach as well here

[meymchen]

A nice implementation is already done here and I did a similar job on my pygls-based project.
If anyone cares, I can make a contribution.

[alcarney]

If anyone cares, I can make a contribution.

If you could that would be awesome! 😄

[meymchen]

If anyone cares, I can make a contribution.

If you could that would be awesome! 😄

Sure, I'd love to take on the task and will do so in my spare time over the next few days.