x/tools/gopls: deprecate 'Structured' hover kind

[findleyr]

The 'Structured' hover kind does not serve human readable hover content. Rather, it serves JSON describing the hover.
https://github.com/golang/tools/blob/master/gopls/doc/settings.md#hoverkind-enum

gopls should conform to the semantics of the LSP: hover is intended to be human readable. If we want to delegate hover presentation to the client, we must by definition have a thick client, in which case the client can just use a separate command via workspace/executeCommand. By analogy, tsserver has a command for structured hover info: https://github.com/microsoft/TypeScript/blob/55f1248a2052eebdea6bc0e2eef754df89a44bf7/src/server/protocol.ts#L2015.

CC @adonovan

[adonovan]

I vaguely recall that the sole thick client of the Hover JSON output is one of the Vims. (The feature was added in the CL attached to #33352. Paging @myitcv for awareness.)

[myitcv]

Paging @myitcv for awareness.

Thanks, @adonovan - we're actually using what I believe the gopls default is in this space, "FullDocumentation":

https://github.com/govim/govim/blob/6280deb8b406332ed0c9f0eea59671d954b815ab/cmd/govim/gopls_client.go#L159

[adonovan]

[govim is] actually using what I believe the gopls default is in this space, "FullDocumentation":

Great, let's remove kind=structured then.

[gopherbot]

Change https://go.dev/cl/635226 mentions this issue: gopls/internal/settings: drop experimental hoverKind=Structured

[bhcleek]

FWIW, vim-go was using Structured.

[findleyr]

@bhcleek very sorry about the breakage :(.

This was, I think, perhaps the first time we've just removed a setting without a probationary release where it is a warning. We really thought the only user was govim -- I'm afraid the similar naming of the clients may have been part of the confusion. Lesson (re)learned.

What can we do to help? We can revert the deprecation temporarily, though that might be messy (I'll try). If instead you can fix forward, that may be cleanest.

Going forward If you need structured information from hover, we can can add a custom command. As described in the release notes, it was a mistake to shoehorn a JSON API into hover.

[bhcleek]

I can probably refactor vim-go to get what I need, but I won't be able to get to it immediately.

IIRC, I'd relied on Structured, because FullDocumentation was missing some things vim-go needed and the structure of the documentation result when FullDocumentation was used did not come with guarantees; parsing free form text is tricky, especially if the server doesn't guarantee its form across versions.

[findleyr]

Reopening and moving to the v0.19.0 milestone, since this deletion is being reverted.