Example of a semi-practical usage of vim.loop.new_work

nvim-luv-new-work.lua

local function async_scandir(dirname, callback)
  local function work_callback(dirname)
    local uv = require('luv')
    local fs, err = uv.fs_scandir(dirname)
    if err then
      return err
    end
    local entry_names = {}
    local entry_types = {}
    local i = 0
    while true do
      local name, type_or_err, err_code = uv.fs_scandir_next(fs)
      if err_code then
        return type_or_err
      elseif not name then
        break
      else
        i = i + 1
        entry_names[i] = name
        entry_types[i] = type_or_err
      end
    end
    return nil, i, table.concat(entry_names, '\0'), table.concat(entry_types, '\0')
  end

  local function work_done_callback(err, entries_count, entry_names, entry_types)
    if err then
      return callback(err)
    end
    entry_names = vim.split(entry_names, '\0')
    entry_types = vim.split(entry_types, '\0')
    assert(#entry_names == entries_count)
    assert(#entry_types == entries_count)
    local entries = {}
    for i = 1, entries_count do
      entries[i] = { name = entry_names[i], type = entry_types[i] }
    end
    callback(nil, entries)
  end

  local work = vim.loop.new_work(work_callback, work_done_callback)
  local _, err = vim.loop.queue_work(work, dirname)
  if err then
    callback(err)
  end
end