Built-in completion + snippet Neovim setup

builtin-compl.lua

    ---Utility for keymap creation.
    ---@param lhs string
    ---@param rhs string|function
    ---@param opts string|table
    ---@param mode? string|string[]
    local function keymap(lhs, rhs, opts, mode)
        opts = type(opts) == 'string' and { desc = opts }
            or vim.tbl_extend('error', opts --[[@as table]], { buffer = bufnr })
        mode = mode or 'n'
        vim.keymap.set(mode, lhs, rhs, opts)
    end

    ---For replacing certain <C-x>... keymaps.
    ---@param keys string
    local function feedkeys(keys)
        vim.api.nvim_feedkeys(vim.api.nvim_replace_termcodes(keys, true, false, true), 'n', true)
    end

    ---Is the completion menu open?
    local function pumvisible()
        return tonumber(vim.fn.pumvisible()) ~= 0
    end

    -- Enable completion and configure keybindings.
    if client.supports_method(methods.textDocument_completion) then
        vim.lsp.completion.enable(true, client.id, bufnr, { autotrigger = true })
        
        -- Use enter to accept completions.
        keymap('<cr>', function()
            return pumvisible() and '<C-y>' or '<cr>'
        end, { expr = true }, 'i')
        
        -- Use slash to dismiss the completion menu.
        keymap('/', function()
            return pumvisible() and '<C-e>' or '/'
        end, { expr = true }, 'i')
    
        -- Use <C-n> to navigate to the next completion or:
        -- - Trigger LSP completion.
        -- - If there's no one, fallback to vanilla omnifunc.
        keymap('<C-n>', function()
            if pumvisible() then
                feedkeys '<C-n>'
            else
                if next(vim.lsp.get_clients { bufnr = 0 }) then
                    vim.lsp.completion.trigger()
                else
                    if vim.bo.omnifunc == '' then
                        feedkeys '<C-x><C-n>'
                    else
                        feedkeys '<C-x><C-o>'
                    end
                end
            end
        end, 'Trigger/select next completion', 'i')
    
        -- Buffer completions.
        keymap('<C-u>', '<C-x><C-n>', { desc = 'Buffer completions' }, 'i')
    
        -- Use <Tab> to accept a Copilot suggestion, navigate between snippet tabstops,
        -- or select the next completion.
        -- Do something similar with <S-Tab>.
        keymap('<Tab>', function()
            local copilot = require 'copilot.suggestion'

            if copilot.is_visible() then
                copilot.accept()
            elseif pumvisible() then
                feedkeys '<C-n>'
            elseif vim.snippet.active { direction = 1 } then
                vim.snippet.jump(1)
            else
                feedkeys '<Tab>'
            end
        end, {}, { 'i', 's' })
        keymap('<S-Tab>', function()
            if pumvisible() then
                feedkeys '<C-p>'
            elseif vim.snippet.active { direction = -1 } then
                vim.snippet.jump(-1)
            else
                feedkeys '<S-Tab>'
            end
        end, {}, { 'i', 's' })

        -- Inside a snippet, use backspace to remove the placeholder.
        keymap('<BS>', '<C-o>s', {}, 's')
    end

is the autotrigger = true supposed to show the autocomplete menu while we are editing the buffer?

I've set it up with it, but when writing in a ts file for example nothing shows up, however pressing <c-x><c-o> does show the autocomplete menu

or do we have to do more configuration to have it working? thanks!

Very cool! I'd like to add:

-- Autoselect the first item but don't insert it.
-- Allows quick use, just write something and enter to select the first one.
vim.opt.completeopt = { "menu", "menuone", "noinsert" }

-- Make completion menu appear whenever you type something.
-- Example from: https://neovim.io/doc/user/lsp.html#lsp-attach
-- Optional: trigger autocompletion on EVERY keypress. May be slow!
local chars = {}
for i = 32, 126 do
	table.insert(chars, string.char(i))
end
client.server_capabilities.completionProvider.triggerCharacters = chars
vim.lsp.completion.enable(true, client.id, args.buf, {
	autotrigger = true,
})

Some things that the built-in completion does not support (yet?):

• Hover documentation next to completion item. It does however support preview if you append "preview" to completeopt.
• Combined menu of both LSP and buffer items. You can only have either one or the other.
• Custom snippet support? I didn't get my custom snippets working. As I understand, this completion only works on LSP server provided completions?

is the autotrigger = true supposed to show the autocomplete menu while we are editing the buffer?

I've set it up with it, but when writing in a ts file for example nothing shows up, however pressing <c-x><c-o> does show the autocomplete menu

or do we have to do more configuration to have it working? thanks!

Just for the record, the native autocomplete will offer suggestions after you press ., i.e. it shows properties and methods. At least in my case, when using tsgo.