nvim-lspconfig + nvim-cmp setup

init.lua

--[[
  blogpost:
  https://vonheikemen.github.io/devlog/tools/setup-nvim-lspconfig-plus-nvim-cmp/

  Dependencies:
  LSP:
  https://github.com/neovim/nvim-lspconfig
  https://github.com/williamboman/mason.nvim             (optional)
  https://github.com/williamboman/mason-lspconfig.nvim   (optional)

  Completion:
  https://github.com/hrsh7th/nvim-cmp
  https://github.com/hrsh7th/cmp-nvim-lsp
  https://github.com/hrsh7th/cmp-buffer
  https://github.com/hrsh7th/cmp-path
  https://github.com/saadparwaiz1/cmp_luasnip
  
  Snippets:
  https://github.com/L3MON4D3/LuaSnip
  https://github.com/rafamadriz/friendly-snippets
]]

---
-- Keybindings
---

vim.api.nvim_create_autocmd('User', {
  pattern = 'LspAttached',
  desc = 'LSP actions',
  callback = function()
    local bufmap = function(mode, lhs, rhs)
      local opts = {buffer = true}
      vim.keymap.set(mode, lhs, rhs, opts)
    end

    bufmap('n', 'K', '<cmd>lua vim.lsp.buf.hover()<cr>')
    bufmap('n', 'gd', '<cmd>lua vim.lsp.buf.definition()<cr>')
    bufmap('n', 'gD', '<cmd>lua vim.lsp.buf.declaration()<cr>')
    bufmap('n', 'gi', '<cmd>lua vim.lsp.buf.implementation()<cr>')
    bufmap('n', 'go', '<cmd>lua vim.lsp.buf.type_definition()<cr>')
    bufmap('n', 'gr', '<cmd>lua vim.lsp.buf.references()<cr>')
    bufmap('n', '<C-k>', '<cmd>lua vim.lsp.buf.signature_help()<cr>')
    bufmap('n', '<F2>', '<cmd>lua vim.lsp.buf.rename()<cr>')
    bufmap('n', '<F4>', '<cmd>lua vim.lsp.buf.code_action()<cr>')
    bufmap('x', '<F4>', '<cmd>lua vim.lsp.buf.range_code_action()<cr>')
    bufmap('n', 'gl', '<cmd>lua vim.diagnostic.open_float()<cr>')
    bufmap('n', '[d', '<cmd>lua vim.diagnostic.goto_prev()<cr>')
    bufmap('n', ']d', '<cmd>lua vim.diagnostic.goto_next()<cr>')
  end
})


---
-- Diagnostics
---

local sign = function(opts)
  vim.fn.sign_define(opts.name, {
    texthl = opts.name,
    text = opts.text,
    numhl = ''
  })
end

sign({name = 'DiagnosticSignError', text = '✘'})
sign({name = 'DiagnosticSignWarn', text = '▲'})
sign({name = 'DiagnosticSignHint', text = '⚑'})
sign({name = 'DiagnosticSignInfo', text = ''})

vim.diagnostic.config({
  virtual_text = false,
  severity_sort = true,
  float = {
    border = 'rounded',
    source = 'always',
    header = '',
    prefix = '',
  },
})

vim.lsp.handlers['textDocument/hover'] = vim.lsp.with(
  vim.lsp.handlers.hover,
  {border = 'rounded'}
)

vim.lsp.handlers['textDocument/signatureHelp'] = vim.lsp.with(
  vim.lsp.handlers.signature_help,
  {border = 'rounded'}
)

---
-- LSP config
---

-- require('mason').setup({})
-- require('mason-lspconfig').setup({})

local lsp_defaults = {
  flags = {
    debounce_text_changes = 150,
  },
  capabilities = require('cmp_nvim_lsp').update_capabilities(
    vim.lsp.protocol.make_client_capabilities()
  ),
  on_attach = function(client, bufnr)
    vim.api.nvim_exec_autocmds('User', {pattern = 'LspAttached'})
  end
}

local lspconfig = require('lspconfig')

lspconfig.util.default_config = vim.tbl_deep_extend(
  'force',
  lspconfig.util.default_config,
  lsp_defaults
)


---
-- LSP servers
---

-- lspconfig.tsserver.setup({})
-- lspconfig.html.setup({})
-- lspconfig.cssls.setup({})
-- lspconfig.sumneko_lua.setup({})


---
-- Autocomplete
---

require('luasnip.loaders.from_vscode').lazy_load()

local cmp = require('cmp')
local luasnip = require('luasnip')

local select_opts = {behavior = cmp.SelectBehavior.Select}

cmp.setup({
  snippet = {
    expand = function(args)
      luasnip.lsp_expand(args.body)
    end
  },
  sources = {
    {name = 'path'},
    {name = 'nvim_lsp', keyword_length = 3},
    {name = 'buffer', keyword_length = 3},
    {name = 'luasnip', keyword_length = 2},
  },
  window = {
    documentation = cmp.config.window.bordered()
  },
  formatting = {
    fields = {'menu', 'abbr', 'kind'},
    format = function(entry, item)
      local menu_icon = {
        nvim_lsp = 'λ',
        luasnip = '⋗',
        buffer = 'Ω',
        path = '🖫',
      }

      item.menu = menu_icon[entry.source.name]
      return item
    end,
  },
  mapping = {
    ['<Up>'] = cmp.mapping.select_prev_item(select_opts),
    ['<Down>'] = cmp.mapping.select_next_item(select_opts),

    ['<C-p>'] = cmp.mapping.select_prev_item(select_opts),
    ['<C-n>'] = cmp.mapping.select_next_item(select_opts),

    ['<C-u>'] = cmp.mapping.scroll_docs(-4),
    ['<C-f>'] = cmp.mapping.scroll_docs(4),

    ['<C-e>'] = cmp.mapping.abort(),
    ['<CR>'] = cmp.mapping.confirm({select = true}),

    ['<C-d>'] = cmp.mapping(function(fallback)
      if luasnip.jumpable(1) then
        luasnip.jump(1)
      else
        fallback()
      end
    end, {'i', 's'}),

    ['<C-b>'] = cmp.mapping(function(fallback)
      if luasnip.jumpable(-1) then
        luasnip.jump(-1)
      else
        fallback()
      end
    end, {'i', 's'}),

    ['<Tab>'] = cmp.mapping(function(fallback)
      local col = vim.fn.col('.') - 1

      if cmp.visible() then
        cmp.select_next_item(select_opts)
      elseif col == 0 or vim.fn.getline('.'):sub(col, col):match('%s') then
        fallback()
      else
        cmp.complete()
      end
    end, {'i', 's'}),

    ['<S-Tab>'] = cmp.mapping(function(fallback)
      if cmp.visible() then
        cmp.select_prev_item(select_opts)
      else
        fallback()
      end
    end, {'i', 's'}),
  },
})