DiagnosticUnnecessary (and possibly other Diagnostic<name>(s)) Are not Being Handled By Onedark

[EightBitBoot]

lua-language-server uses DiagnosticUnnecessary for unused local variables and empty code blocks. This is great for development, however - by default - DiagnosticUnnecessary links to Comment: graying out entire function definitions / control blocks (including the start and end lines) and making those regions extremely hard to read.

The lua-language-server documentation for the unused diagnostic states that the text becomes slightly transparent (I'm assuming this is the effect produced by vscode) which would be a cool idea, if possible (perhaps by using a slightly darkened palette of the same colors).

The quick and dirty workaround I found (here) is to run

:highlight! link DiagnosticUnnecessary WarningText

but that only disables the comment formatting.

Linking DiagnosticUnnecessary to DiagnosticUnderlineWarn produces ugly underlines on leading whitespace (space indented)

and linking to DiagnosticWarn turns the contents of the function yellow.

I'm not sure the best approach to fix this (while also sticking to onedark conventions) so I'm posting this as an issue. If whoever is reading this comes up with an appropriate solution, I would be more than happy to make the changes and a pull request.

P.S. DiagnosticUnnecessary and DiagnosticDeprecated were previously supported but undocumented neovim/neovim#22931

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Versioning Info

Component	Version
neovim	v0.10.1
lazy.nvim	v11.14.1
onedark	branch: master; commit: fae34f7
lua-language-server	lua-language-server --version reports <Unknown>, however my package manager reports 3.10.1