nvim-lspconfig/lsp/mesonlsp.lua

---@brief
---
--- https://github.com/JCWasmx86/mesonlsp
---
--- An unofficial, unendorsed language server for meson written in C++

---Checks if a given path contains a valid Meson project root file
---Looks for 'meson.build' file which contains 'project()' function
local meson_matcher = function(_, path)
  local pattern = 'meson.build'
  local f = vim.fn.glob(table.concat({ path, pattern }, '/'))
  if f == '' then
    return false
  end
  for line in io.lines(f) do
    -- skip meson comments
    if not line:match '^%s*#.*' then
      local str = line:gsub('%s+', '')
      if str ~= '' then
        if str:match '^project%(' then
          return true
        else
          break
        end
      end
    end
  end
  return false
end

---@type vim.lsp.Config
return {
  cmd = { 'mesonlsp', '--lsp' },
  filetypes = { 'meson' },
  root_dir = function(bufnr, on_dir)
    on_dir(vim.fs.root(bufnr, meson_matcher) or vim.fs.root(bufnr, '.git'))
  end,
}