Neovim 0.11 config with builtin autocompletion

init.lua

---[[HOW TO USE IT?
--- 0. Install neovim 0.11
--- 1. Create ~/.config/nvim-experiments directory on your machine (Assuming you are using Linux)
--- 2. Copy this init.lua into the nvim-experiments directory
--- 3. Launch neovim using `NVIM_APPNAME=nvim-experiments nvim` command
--- 4. Install requiring lsp servers via mason (type `:Mason`), relaunch neovim, and open your project to test it
--- 5. You may want to install treesitter parsers to get documentation
--- highlighting for some languages
---]]

---[[ Lazy.nvim package manager bootstrap and some essential plugins installation
local lazypath = vim.fn.stdpath("data") .. "/lazy/lazy.nvim"
if not vim.uv.fs_stat(lazypath) then
  local lazyrepo = "https://github.com/folke/lazy.nvim.git"
  vim.fn.system({ "git", "clone", "--filter=blob:none", "--branch=stable", lazyrepo, lazypath })
end
vim.opt.rtp:prepend(lazypath)

require("lazy").setup({
  spec = {
    { "williamboman/mason.nvim",          opts = {} },
    { "folke/lazydev.nvim",               opts = {} },
    { "neovim/nvim-lspconfig" },
    { "williamboman/mason-lspconfig.nvim" },
    {
      "williamboman/mason.nvim",
      config = function()
        require("mason").setup()
        require("mason-lspconfig").setup()
        require("mason-lspconfig").setup_handlers({
          function(server_name)
            require("lspconfig")[server_name].setup({})
          end,
        })
      end
    },
    { "j-hui/fidget.nvim",     opts = {}, },
    { "folke/tokyonight.nvim", priority = 1000, opts = {} },
  },
})
vim.cmd [[colorscheme tokyonight-moon]]
vim.o.number = true
vim.o.signcolumn = "yes"
vim.cmd([[autocmd FileType * set formatoptions-=ro]]) -- disable new line auto comment
---]]


---[[AUTOCOMPLETION SETUP
vim.o.completeopt = "menu,noinsert,popup,fuzzy"

---[[ Setup keymaps so we can accept completion using Enter and choose items using arrow keys or Tab.
local pumMaps = {
  ['<Tab>'] = '<C-n>',
  ['<S-Tab>'] = '<C-p>',
  ['<Down>'] = '<C-n>',
  ['<Up>'] = '<C-p>',
  ['<CR>'] = '<C-y>',
}
for insertKmap, pumKmap in pairs(pumMaps) do
  vim.keymap.set('i', insertKmap, function()
    return vim.fn.pumvisible() == 1 and pumKmap or insertKmap
  end, { expr = true })
end
---]]

vim.api.nvim_create_autocmd('LspAttach', {
  callback = function(args)
    ---[[Code required to activate autocompletion and trigger it on each keypress
    local client = assert(vim.lsp.get_client_by_id(args.data.client_id))
    client.server_capabilities.completionProvider.triggerCharacters = vim.split("qwertyuiopasdfghjklzxcvbnm. ", "")
    vim.api.nvim_create_autocmd({ 'TextChangedI' }, {
      buffer = args.buf,
      callback = function()
        vim.lsp.completion.get()
      end
    })
    vim.lsp.completion.enable(true, client.id, args.buf, { autotrigger = true })
    ---]]

    ---[[Code required to add documentation popup for an item
    local _, cancel_prev = nil, function() end
    vim.api.nvim_create_autocmd('CompleteChanged', {
      buffer = args.buf,
      callback = function()
        cancel_prev()
        local info = vim.fn.complete_info({ 'selected' })
        local completionItem = vim.tbl_get(vim.v.completed_item, 'user_data', 'nvim', 'lsp', 'completion_item')
        if nil == completionItem then
          return
        end
        _, cancel_prev = vim.lsp.buf_request(args.buf,
          vim.lsp.protocol.Methods.completionItem_resolve,
          completionItem,
          function(err, item, ctx)
            if not item then
              return
            end
            local docs = (item.documentation or {}).value
            local win = vim.api.nvim__complete_set(info['selected'], { info = docs })
            if win.winid and vim.api.nvim_win_is_valid(win.winid) then
              vim.treesitter.start(win.bufnr, 'markdown')
              vim.wo[win.winid].conceallevel = 3
            end
          end)
      end
    })
    ---]]
  end
})
---AUTOCOMPLETION SETUP END]]