Snippets

Snippet support can be easily added to your config by installing an autocompletion plugin (such as compe) and a snippets plugins (such as LuaSnip):

To enable snippets support for a given server with LuaSnip, the main steps are to:

• override the capabilities we send to a language server to let it know we support snippets
• set up your snippets source, and the autocompletion plugin to acknowledge the snippets source
• map the confirm and expand snippets keybinds.

nvim-cmp and luasnip

local use = require('packer').use
require('packer').startup(function()
  use 'neovim/nvim-lspconfig' -- Collection of configurations for built-in LSP client
  use 'hrsh7th/nvim-cmp' -- Autocompletion plugin
  use 'hrsh7th/cmp-nvim-lsp' -- LSP source for nvim-cmp
  use 'saadparwaiz1/cmp_luasnip' -- Snippets source for nvim-cmp
  use 'L3MON4D3/LuaSnip' -- Snippets plugin
end)

-- Add additional capabilities supported by nvim-cmp
local capabilities = vim.lsp.protocol.make_client_capabilities()
capabilities.textDocument.completion.completionItem.documentationFormat = { 'markdown', 'plaintext' }
capabilities.textDocument.completion.completionItem.snippetSupport = true
capabilities.textDocument.completion.completionItem.preselectSupport = true
capabilities.textDocument.completion.completionItem.insertReplaceSupport = true
capabilities.textDocument.completion.completionItem.labelDetailsSupport = true
capabilities.textDocument.completion.completionItem.deprecatedSupport = true
capabilities.textDocument.completion.completionItem.commitCharactersSupport = true
capabilities.textDocument.completion.completionItem.tagSupport = { valueSet = { 1 } }
capabilities.textDocument.completion.completionItem.resolveSupport = {
  properties = {
    'documentation',
    'detail',
    'additionalTextEdits',
  },
}

-- Enable some language servers with the additional completion capabilities offered by nvim-cmp
local servers = { 'clangd', 'rust_analyzer', 'pyright', 'tsserver' }
for _, lsp in ipairs(servers) do
  nvim_lsp[lsp].setup {
    -- on_attach = my_custom_on_attach,
    capabilities = capabilities,
  }
end

-- luasnip setup
local luasnip = require 'luasnip'

-- nvim-cmp setup
local cmp = require 'cmp'
cmp.setup {
  snippet = {
    expand = function(args)
      require('luasnip').lsp_expand(args.body)
    end,
  },
  mapping = {
    ['<C-p>'] = cmp.mapping.select_prev_item(),
    ['<C-n>'] = cmp.mapping.select_next_item(),
    ['<C-d>'] = cmp.mapping.scroll_docs(-4),
    ['<C-f>'] = cmp.mapping.scroll_docs(4),
    ['<C-Space>'] = cmp.mapping.complete(),
    ['<C-e>'] = cmp.mapping.close(),
    ['<CR>'] = cmp.mapping.confirm {
      behavior = cmp.ConfirmBehavior.Replace,
      select = true,
    },
    ['<Tab>'] = cmp.mapping(function(fallback)
      if vim.fn.pumvisible() == 1 then
        vim.fn.feedkeys(vim.api.nvim_replace_termcodes('<C-n>', true, true, true), 'n')
      elseif luasnip.expand_or_jumpable() then
        vim.fn.feedkeys(vim.api.nvim_replace_termcodes('<Plug>luasnip-expand-or-jump', true, true, true), '')
      else
        fallback()
      end
    end, { 'i', 's' }),
    ['<S-Tab>'] = cmp.mapping(function(fallback)
      if vim.fn.pumvisible() == 1 then
        vim.fn.feedkeys(vim.api.nvim_replace_termcodes('<C-p>', true, true, true), 'n')
      elseif luasnip.jumpable(-1) then
        vim.fn.feedkeys(vim.api.nvim_replace_termcodes('<Plug>luasnip-jump-prev', true, true, true), '')
      else
        fallback()
      end
    end, { 'i', 's' }),
  },
  sources = {
    { name = 'nvim_lsp' },
    { name = 'luasnip' },
  },
}

nvim-compe and luasnip

Here is a complete example for compe and LuaSnip:

local capabilities = vim.lsp.protocol.make_client_capabilities()
capabilities.textDocument.completion.completionItem.snippetSupport = true

-- Enable the following language servers
local servers = { 'clangd', 'rust_analyzer', 'pyright', 'tsserver' }
for _, lsp in ipairs(servers) do
  require('lspconfig')[lsp].setup {
    -- You will probably want to add a custom on_attach here to locally map keybinds to buffers with an active client
    -- on_attach = on_attach,
    capabilities = capabilities,
  }
end

-- Set completeopt to have a better completion experience
vim.o.completeopt = 'menuone,noinsert'

-- Compe setup
require('compe').setup {
  source = {
    path = true,
    nvim_lsp = true,
    luasnip = true,
    buffer = true,
    calc = false,
    nvim_lua = false,
    vsnip = false,
    ultisnips = false,
  },
}

-- Utility functions for compe and luasnip
local t = function(str)
  return vim.api.nvim_replace_termcodes(str, true, true, true)
end

local check_back_space = function()
  local col = vim.fn.col '.' - 1
  if col == 0 or vim.fn.getline('.'):sub(col, col):match '%s' then
    return true
  else
    return false
  end
end

-- Use (s-)tab to:
--- move to prev/next item in completion menu
--- jump to prev/next snippet's placeholder
local luasnip = require 'luasnip'

_G.tab_complete = function()
  if vim.fn.pumvisible() == 1 then
    return t '<C-n>'
  elseif luasnip.expand_or_jumpable() then
    return t '<Plug>luasnip-expand-or-jump'
  elseif check_back_space() then
    return t '<Tab>'
  else
    return vim.fn['compe#complete']()
  end
end

_G.s_tab_complete = function()
  if vim.fn.pumvisible() == 1 then
    return t '<C-p>'
  elseif luasnip.jumpable(-1) then
    return t '<Plug>luasnip-jump-prev'
  else
    return t '<S-Tab>'
  end
end

-- Map tab to the above tab complete functions
vim.api.nvim_set_keymap('i', '<Tab>', 'v:lua.tab_complete()', { expr = true })
vim.api.nvim_set_keymap('s', '<Tab>', 'v:lua.tab_complete()', { expr = true })
vim.api.nvim_set_keymap('i', '<S-Tab>', 'v:lua.s_tab_complete()', { expr = true })
vim.api.nvim_set_keymap('s', '<S-Tab>', 'v:lua.s_tab_complete()', { expr = true })

-- Map compe confirm and complete functions
vim.api.nvim_set_keymap('i', '<cr>', 'compe#confirm("<cr>")', { expr = true })
vim.api.nvim_set_keymap('i', '<c-space>', 'compe#complete()', { expr = true })