Semanticist.nvim

NO LONGER REQUIRED

Just a note for the handful of people who used this: you don't need it after 2023-03-06, when this PR was merged into neovim nightly. See:

• :h lsp-semantic-highlight
• :h LspTokenUpdate

Control how neovim uses LSP semantic tokens to apply highlights. Requires neovim nightly.

Warning

This is experimental, unstable, etc.

Use

Set up the plugin as usual:

require('semanticist').setup()

Then add a custom highlighter for a filetype:

require('semanticist').highlighters[ft] = function(bufnr, ns, token)
  -- Add extmarks here
end

Or change the default:

require('semanticist').default_highlighter = function(bufnr, ns, token)
  -- Add extmarks here
end

An example with clangd

Here are the types of semantic tokens sent by clangd:

variable        parameter       function        method
function        property        class           interface
enum            enumMember      type            unknown
namespace       typeParameter   concept         type
macro           modifier        operator        comment

The modifiers clangd uses are:

functionScope   classScope      fileScope       globalScope
declaration     definition      deprecated      readonly
static          deduced         abstract        virtual
dependentName   usedAsMutableReference
userDefined     usedAsMutablePointer
defaultLibrary  constructorOrDestructor

Some of the modifiers are mutually exclusive, like functionScope and classScope. Others can be combined, like static and readonly.

For this example, I want to differentiate scopes, then apply an additional highlight for deprecated tokens.

semanticist.highlighters["cpp"] = function(bufnr, ns, token)

  local mark = function(hl_group, delta)
    delta = delta or 0
    vim.api.nvim_buf_set_extmark(bufnr, ns, token.line, token.start_col, {
      hl_group = hl_group,
      end_col = token.end_col,
      priority = vim.highlight.priorities.semantic_tokens + delta,
      strict = false,
    })
  end

  local mods = token.modifiers
  vim.tbl_add_reverse_lookup(mods)

  local scope = mods.functionScope and ".functionScope"
    or mods.globalScope and ".globalScope"
    or mods.classScope and ".classScope"
    or mods.fileScope and ".fileScope"
    or ""
  mark(string.format("@%s.cpp%s", token.type, scope))

  if mods.deprecated then mark("LspDeprecated", 1) end
end

Then add highlight groups as desired:

hi @variable.cpp.functionScope ...
hi @variable.cpp.localScope ...
...
hi LspDeprecated gui=strikethrough