x/tools/gopls: add insert-replace support (insertReplaceEdit)

[muirdm]

Currently gopls is overwriting the surrounding suffix (in addition to prefix) when inserting candidates:

// completing to "food" currently results in "food" instead of "foodoo"
f<>oo

I think it's from https://go-review.googlesource.com/c/tools/+/208501 changing the surrounding's range from [ident.Pos(), c.pos] to [ident.Pos(), ident.End()].

/cc @heschik

[schellj]

I'm not familiar with this codebase, but it appears that there might already be a commit relevant to a fix for this issue at https://go-review.googlesource.com/c/tools/+/196119/. There's also a related issue report that was frozen due to age at #34011.

[schellj]

Also relevant to this behavior is the LSP client's insertReplaceSupport capability property (see https://microsoft.github.io/language-server-protocol/specification). If the client has that capability, the server is supposed to return two edit ranges; one for inserting the completion and one for replacing existing text with the completion.

[muirdm]

This issue regressed since it was fixed in https://go-review.googlesource.com/c/tools/+/196119/ .

insertReplaceSupport

Interesting. Adding support for that could be the best way forward since preferences differ.

[zikaeroh]

Selfishly, I still prefer the behavior I advocated for in #34011, so any way that preserves the behavior will make me happy. 🙂

[schellj]

@zikaeroh I generally agree. However, it seems that according to the LSP spec, supporting insertReplaceSupport seems to be the way that the server would ideally resolve this preference between users (or even each given completion selection).

Sorry, I failed to read the second part of your comment 😊

[ackerr]

Is anyone following up

[elliebodi]

I don't have time at the moment to implement the insertReplaceSupport capability, but I prefer not to have the suffix replaced, so I forked gopls and made this change to get my desired behavior.

I'll try to revisit at some point and implement the capability.