clangd.lua

local util = require 'lspconfig.util'

-- https://clangd.llvm.org/extensions.html#switch-between-sourceheader
local function switch_source_header(bufnr)
  local method_name = 'textDocument/switchSourceHeader'
  bufnr = util.validate_bufnr(bufnr)
  local client = util.get_active_client_by_name(bufnr, 'clangd')
  if not client then
    return vim.notify(('method %s is not supported by any servers active on the current buffer'):format(method_name))
  end
  local params = vim.lsp.util.make_text_document_params(bufnr)
  client.request(method_name, params, function(err, result)
    if err then
      error(tostring(err))
    end
    if not result then
      vim.notify('corresponding file cannot be determined')
      return
    end
    vim.cmd.edit(vim.uri_to_fname(result))
  end, bufnr)
end

local function symbol_info()
  local bufnr = vim.api.nvim_get_current_buf()
  local clangd_client = util.get_active_client_by_name(bufnr, 'clangd')
  if not clangd_client or not clangd_client.supports_method 'textDocument/symbolInfo' then
    return vim.notify('Clangd client not found', vim.log.levels.ERROR)
  end
  local win = vim.api.nvim_get_current_win()
  local params = vim.lsp.util.make_position_params(win, clangd_client.offset_encoding)
  clangd_client.request('textDocument/symbolInfo', params, function(err, res)
    if err or #res == 0 then
      -- Clangd always returns an error, there is not reason to parse it
      return
    end
    local container = string.format('container: %s', res[1].containerName) ---@type string
    local name = string.format('name: %s', res[1].name) ---@type string
    vim.lsp.util.open_floating_preview({ name, container }, '', {
      height = 2,
      width = math.max(string.len(name), string.len(container)),
      focusable = false,
      focus = false,
      border = 'single',
      title = 'Symbol Info',
    })
  end, bufnr)
end

return {
  default_config = {
    cmd = { 'clangd' },
    filetypes = { 'c', 'cpp', 'objc', 'objcpp', 'cuda', 'proto' },
    root_dir = function(fname)
      return util.root_pattern(
        '.clangd',
        '.clang-tidy',
        '.clang-format',
        'compile_commands.json',
        'compile_flags.txt',
        'configure.ac' -- AutoTools
      )(fname) or vim.fs.dirname(vim.fs.find('.git', { path = fname, upward = true })[1])
    end,
    single_file_support = true,
    capabilities = {
      textDocument = {
        completion = {
          editsNearCursor = true,
        },
      },
      offsetEncoding = { 'utf-8', 'utf-16' },
    },
  },
  commands = {
    ClangdSwitchSourceHeader = {
      function()
        switch_source_header(0)
      end,
      description = 'Switch between source/header',
    },
    ClangdShowSymbolInfo = {
      function()
        symbol_info()
      end,
      description = 'Show symbol info',
    },
  },
  docs = {
    description = [[
https://clangd.llvm.org/installation.html

- **NOTE:** Clang >= 11 is recommended! See [#23](https://github.com/neovim/nvim-lspconfig/issues/23).
- If `compile_commands.json` lives in a build directory, you should
  symlink it to the root of your source tree.
  ```
  ln -s /path/to/myproject/build/compile_commands.json /path/to/myproject/
  ```
- clangd relies on a [JSON compilation database](https://clang.llvm.org/docs/JSONCompilationDatabase.html)
  specified as compile_commands.json, see https://clangd.llvm.org/installation#compile_commandsjson
]],
  },
}