Unable to autocomplete with lsp using mason.nvim and nvim-cmp with ultisnips

Question

I'm using neovim to edit my LaTeX and python projects, using packer to be my plugin manager. I'm trying to use lsp along with ultisnips to autocomplete, and for now the ultisnips works very well but lsp doesn't work. Here is my configures.

-- lsp.lua
require("mason").setup({
  ui = {
      icons = {
          package_installed = "✓",
          package_pending = "➜",
          package_uninstalled = "✗"
      }
  }
})

require("mason-lspconfig").setup({
  ensure_installed = {
    "lua_ls",
    "clangd",
    "jsonls",
    -- "ltex",
    -- "texlab",
    "pylsp",
    -- "pylyzer",
    "vimls"
  }
})

local capabilities = require('cmp_nvim_lsp').default_capabilities()

require("lspconfig").lua_ls.setup {
  capabilities = capabilities,
}

-- cmp.lua
local cmp = require'cmp'
local cmp_ultisnips_mappings = require'cmp_nvim_ultisnips.mappings'

local t = function(str)
    return vim.api.nvim_replace_termcodes(str, true, true, true)
end

cmp.setup({
  preselect = cmp.PreselectMode.None,
  snippet = {
    expand = function(args)
      vim.fn["UltiSnips#Anon"](args.body)
    end,
  },
  mapping = {
    ['<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({ select = true }),
    ['<tab>'] = cmp.mapping(function(fallback)
      if cmp.visible() then
        cmp.select_next_item({ behavior = cmp.SelectBehavior.Select })
        -- cmp.confirm({ select = true })
      else
        cmp_ultisnips_mappings.jump_forwards(fallback)
      end
    end, { 'i', 's' }),
    -- ["<Tab>"] = cmp.mapping({
    --   i = function(fallback)
    --     if cmp.visible() then
    --       cmp.select_next_item({ behavior = cmp.SelectBehavior.Select })
    --     else
    --       cmp_ultisnips_mappings.jump_forwards(fallback)
    --     end
    --   end,
    -- }),
    -- ["<Tab>"] = cmp.mapping({
    --   c = function()
    --     if cmp.visible() then
    --       cmp.select_next_item({ behavior = cmp.SelectBehavior.Insert })
    --     else
    --       cmp.complete()
    --     end
    --   end,
    --   i = function(fallback)
    --     if cmp.visible() and vim.fn["UltiSnips#CanJumpForwards"]() == 1 then
    --       vim.api.nvim_feedkeys(t("<Plug>(ultisnips_jump_forward)"), 'm', true)
    --     elseif cmp.visible() then
    --       cmp.select_next_item({ behavior = cmp.SelectBehavior.Select })
    --     elseif vim.fn["UltiSnips#CanJumpForwards"]() == 1 then
    --       vim.api.nvim_feedkeys(t("<Plug>(ultisnips_jump_forward)"), 'm', true)
    --     else
    --       fallback()
    --     end
    --   end,
    --   s = function(fallback)
    --     if vim.fn["UltiSnips#CanJumpForwards"]() == 1 then
    --       vim.api.nvim_feedkeys(t("<Plug>(ultisnips_jump_forward)"), 'm', true)
    --     else
    --       fallback()
    --     end
    --   end
    -- }),
    ['<S-tab>'] = cmp.mapping(function(fallback)
      if cmp.visible() then
        cmp.select_prev_item()
      else
        cmp_ultisnips_mappings.jump_backwards(fallback)
      end
    end, { 'i', 's' }),
  },
  sources = cmp.config.sources({
    { name = 'nvim_lsp' },
    { name = 'nvim_lua' },
    { name = 'ultisnips' },
    { name = 'path' },
  }, {
    { name = 'buffer', keyword_length = 5},
  }),
})

-- plugins-setup.lua
local ensure_packer = function()
  local fn = vim.fn
  local install_path = fn.stdpath('data')..'/site/pack/packer/start/packer.nvim'
  if fn.empty(fn.glob(install_path)) > 0 then
    fn.system({'git', 'clone', '--depth', '1', 'https://github.com/wbthomason/packer.nvim', install_path})
    vim.cmd [[packadd packer.nvim]]
    return true
  end
  return false
end

local packer_bootstrap = ensure_packer()

vim.cmd([[
    augroup pacer_user_config
        autocmd!
        autocmd BufWritePost plugins-setup.lua source <afile> | PackerSync
    augroup end
]])

return require('packer').startup(function(use)
  use 'wbthomason/packer.nvim'
  use 'EdenEast/nightfox.nvim'
  use {
    'nvim-lualine/lualine.nvim',
    requires = { 'nvim-tree/nvim-web-devicons', opt = true }
  }
  use 'nvim-tree/nvim-web-devicons'
  use {
    'nvim-tree/nvim-tree.lua',
    requires = {
      'nvim-tree/nvim-web-devicons', -- optional
    }
  }
  use("christoomey/vim-tmux-navigator")
  use("nvim-treesitter/nvim-treesitter")
  use("p00f/nvim-ts-rainbow")
  use{
    "williamboman/mason.nvim",
    "williamboman/mason-lspconfig.nvim",
    "neovim/nvim-lspconfig",
    "mfussenegger/nvim-dap",
    "jose-elias-alvarez/null-ls.nvim"
  }

  use "hrsh7th/nvim-cmp"
  use "hrsh7th/cmp-nvim-lsp"
  use "hrsh7th/cmp-nvim-lua"
  use "hrsh7th/cmp-path"

  use "numToStr/Comment.nvim"
  use "windwp/nvim-autopairs"

  use "akinsho/bufferline.nvim"
  use "lewis6991/gitsigns.nvim"

  use {
    'nvim-telescope/telescope.nvim', tag = '0.1.1',
    requires = { {
        'nvim-lua/plenary.nvim',
        'BurntSushi/ripgrep',
        'sharkdp/fd'
      } }
  }

  -- Lua
  use {
    "folke/which-key.nvim",
    config = function()
      vim.o.timeout = true
      vim.o.timeoutlen = 300
      require("which-key").setup {}
    end
  }
  use 'lervag/vimtex'
  -- use 'ybian/smartim'

  use 'SirVer/ultisnips'

  use "quangnguyen30192/cmp-nvim-ultisnips"

  if packer_bootstrap then
    require('packer').sync()
  end
end)

I believe that there is something I didn't open or just not install. How can I fix this? Or how can I debug to locate the problem?

Answer 1

I don't know your setup, but I think, you are missing the setup of your lsp (got to be done for every lsp). There you config the Mapping 'key shortcuts <-> functionality of the lsp'.

Mapping: LSP-DEFAULTS -- includes: go to definition, - declaration, hover, signature help, type definition, rename, codeaction, reference, formatting, refactor -- 'on_attach' means: {on_attach} Callback (client, bufnr) invoked when client attaches to a buffer.

Here is a code snippet of my config.

• Mapping Diagnostics

require("mason").setup()
require("mason-lspconfig").setup()

local opts = { noremap = true, silent = true }
vim.keymap.set('n', '<leader>e', vim.diagnostic.open_float, opts)
vim.keymap.set('n', '[d', vim.diagnostic.goto_prev, opts)
vim.keymap.set('n', ']d', vim.diagnostic.goto_next, opts)
vim.keymap.set('n', '<leader>q', vim.diagnostic.setloclist, opts)

• Mapping LSP Defaults

local on_attach = function(client, bufnr)
    local opts_buffer = { noremap = true, silent = true, buffer = bufnr }
    vim.api.nvim_buf_set_option(bufnr, 'omnifunc', 'v:lua.vim.lsp.omnifunc')
    -- Mappings: LSP
    -- See `:help vim.lsp.*` for documentation on any of the below functions
    vim.keymap.set('n', 'gt', vim.lsp.buf.type_definition, opts_buffer)
    vim.keymap.set('n', 'gD', vim.lsp.buf.declaration, opts_buffer)
    vim.keymap.set('n', 'gd', vim.lsp.buf.definition, opts_buffer)
    vim.keymap.set('n', 'K', vim.lsp.buf.hover, opts_buffer)
    vim.keymap.set('n', 'gi', vim.lsp.buf.implementation, opts_buffer)
    vim.keymap.set('n', '<C-k>', vim.lsp.buf.signature_help, opts_buffer)
    vim.keymap.set('n', '<leader>wa', vim.lsp.buf.add_workspace_folder, opts_buffer)
    vim.keymap.set('n', '<leader>wr', vim.lsp.buf.remove_workspace_folder, opts_buffer)
    vim.keymap.set('n', '<space>wl', function() print(vim.inspect(vim.lsp.buf.list_workspace_folders())) end, opts_buffer)
    vim.keymap.set('n', '<leader>D', vim.lsp.buf.type_definition, opts_buffer)
    vim.keymap.set('n', '<leader>rn', vim.lsp.buf.rename, opts_buffer)
    vim.keymap.set('n', '<leader>ca', vim.lsp.buf.code_action, opts_buffer)
    vim.keymap.set('n', 'gr', vim.lsp.buf.references, opts_buffer)
    vim.keymap.set('n', '<leader>f', '<cmd>lua vim.lsp.buf.format({ async = true })<CR>', opts_buffer)
end

local lsp_flags = {
    debounce_text_changes = 150,
}

• Now setting the mapping for each LSP

-- LANGUAGE SPECIFIC LSP Settings 
-- C++
--
require('lspconfig')['clangd'].setup({
    -- LSP-default-keymaps
    on_attach = on_attach,
    flags = lsp_flags,
})

The pattern goes like this:

require('lspconfig')['specificLSP'].setup({
    -- LSP-default-keymaps
    on_attach = on_attach,
    flags = lsp_flags,
    -- Add or override default settings with lsp-specific setting
    setting = {...}
    vim.keymap.set(...do something else...)
})

Example:
```lua
require('lspconfig')['lua_ls'].setup({
    -- LSP-default-keymaps
    on_attach = on_attach,
    flags = lsp_flags,
    settings = {
        Lua = {
            runtime = {
                -- Tell the language server which version of Lua you're using (most likely LuaJIT in the case of Neovim)
                version = 'LuaJIT',
                -- Setup your lua path
                path = runtime_path,
            },
            diagnostics = {
                -- Get the language server to recognize the `vim` global
                globals = { 'vim' },
            },
            workspace = {
                -- Make the server aware of Neovim runtime files
                library = vim.api.nvim_get_runtime_file('', true),
                checkThirdParty = false,
            },
            -- Do not send telemetry data containing a randomized but unique identifier
            telemetry = {
                enable = false,
            },
        },
    },
    commands = {
        Format = {
            function()
                require('stylua-nvim').format_file()
            end,
        },
    },
})

Additional source: neovim/nvim-lspconfig: Quickstart configs for Nvim LSP https://github.com/neovim/nvim-lspconfig#suggested-configuration