init.lua with treesitter, LSP and completion

init.lua

vim.opt.shiftwidth=4
vim.opt.expandtab = true
vim.opt.tabstop = 4
vim.opt.softtabstop = 4
vim.opt.smartindent = true
vim.opt.number = true
vim.opt.relativenumber = true
vim.opt.ignorecase = true
vim.opt.smartcase = true
vim.opt.swapfile = false
vim.opt.backup = false
vim.opt.scrolloff = 5
vim.opt.completeopt = "menuone,noinsert,noselect"
vim.opt.signcolumn = "number"
vim.opt.updatetime = 300
vim.opt.shortmess:append('c')
vim.opt.mouse = 'a'
vim.opt.clipboard = "unnamedplus"

-- only show cursorline in the current split
vim.cmd [[
augroup CursorLine
    au!
    au VimEnter,WinEnter,BufWinEnter * setlocal cursorline
    au WinLeave * setlocal nocursorline
augroup END
]]

require'packer'.startup(function()
    use 'nvim-lua/popup.nvim'
    use 'nvim-lua/plenary.nvim'
    use 'nvim-telescope/telescope.nvim'
    use 'gruvbox-community/gruvbox'
    use 'tpope/vim-commentary'
    use 'tpope/vim-rhubarb'
    use 'tpope/vim-fugitive'
    use 'airblade/vim-gitgutter'
    use {
        'nvim-lualine/lualine.nvim',
        requires = {'kyazdani42/nvim-web-devicons', opt = true}
    }
    use 'cohama/lexima.vim'
    use 'nvim-treesitter/nvim-treesitter'
    use 'JoosepAlviste/nvim-ts-context-commentstring'
    use 'neovim/nvim-lspconfig'
    use 'williamboman/nvim-lsp-installer'
    use 'hrsh7th/cmp-nvim-lsp'
    use 'hrsh7th/cmp-buffer'
    use 'hrsh7th/cmp-path'
    use 'hrsh7th/cmp-cmdline'
    use 'hrsh7th/nvim-cmp'
    use 'hrsh7th/cmp-vsnip'
    use 'hrsh7th/vim-vsnip'
end)

require'lualine'.setup {
  options = {
    icons_enabled = true,
    theme = 'gruvbox',
    component_separators = { left = '', right = ''},
    section_separators = { left = '', right = ''},
    disabled_filetypes = {},
    always_divide_middle = true,
  },
  sections = {
    lualine_a = {'mode'},
    lualine_b = {'branch', 'diff', 'diagnostics'},
    lualine_c = {'filename'},
    lualine_x = {'encoding', 'fileformat', 'filetype'},
    lualine_y = {'progress'},
    lualine_z = {'location'}
  },
  inactive_sections = {
    lualine_a = {},
    lualine_b = {},
    lualine_c = {'filename'},
    lualine_x = {'location'},
    lualine_y = {},
    lualine_z = {}
  },
  tabline = {},
  extensions = {'fugitive'}
}

require'nvim-treesitter.configs'.setup{
    ensure_installed = "maintained", -- Only use parsers that are maintained
    highlight = {
        enable = true,
    },
    indent = {
        enable = true,
    },
    context_commentstring = {
        enable = true
    }
}

-- Setup lspconfig.
local capabilities = require('cmp_nvim_lsp').update_capabilities(vim.lsp.protocol.make_client_capabilities())

require'nvim-lsp-installer'.on_server_ready(function(server)
    local opts = { capabilities = capabilities }
    if server.name == "sumneko_lua" then
    opts = {
      settings = {
        Lua = {
          diagnostics = {
            globals = { 'vim', 'use' }
          },
        }
      },
      capabilities = capabilities
    }
    end
    server:setup(opts)
end)

local cmp = require'cmp'

cmp.setup({
    snippet = {
        expand = function(args)
            vim.fn["vsnip#anonymous"](args.body)
        end,
    },
    mapping = {
        ['<C-b>'] = cmp.mapping(cmp.mapping.scroll_docs(-4), { 'i', 'c' }),
        ['<C-f>'] = cmp.mapping(cmp.mapping.scroll_docs(4), { 'i', 'c' }),
        ['<C-Space>'] = cmp.mapping(cmp.mapping.complete(), { 'i', 'c' }),
        ['<C-y>'] = cmp.config.disable, -- Specify `cmp.config.disable` if you want to remove the default `<C-y>` mapping.
        ['<C-e>'] = cmp.mapping({
            i = cmp.mapping.abort(),
            c = cmp.mapping.close(),
        }),
        -- Accept currently selected item. If none selected, `select` first item.
        -- Set `select` to `false` to only confirm explicitly selected items.
        ['<CR>'] = cmp.mapping.confirm({ select = true }),
    },
    sources = cmp.config.sources({
        { name = 'nvim_lsp' },
        -- { name = 'vsnip' }, -- For vsnip users.
        -- { name = 'luasnip' }, -- For luasnip users.
        -- { name = 'ultisnips' }, -- For ultisnips users.
        -- { name = 'snippy' }, -- For snippy users.
    }, {
            { name = 'buffer' },
        })
})

-- Use buffer source for `/` (if you enabled `native_menu`, this won't work anymore).
cmp.setup.cmdline('/', {
    sources = {
        { name = 'buffer' }
    }
})

-- Use cmdline & path source for ':' (if you enabled `native_menu`, this won't work anymore).
cmp.setup.cmdline(':', {
    sources = cmp.config.sources({
        { name = 'path' }
    }, {
            { name = 'cmdline' }
        })
})

vim.opt.termguicolors = true
vim.g.gruvbox_italics = 1
vim.cmd[[colorscheme gruvbox]]

-- key mappings

vim.g.mapleader = " "

local keymap = vim.api.nvim_set_keymap
local opts = { noremap = true }
-- keep things centered when searching or joining lines
keymap('n', 'n', 'nzzzv', opts)
keymap('n', 'N', 'Nzzzv', opts)
keymap('n', 'J', 'mzJ`z', opts)

-- undo break points, only undoes until these
keymap('i', ',', ',<c-g>u', opts)
keymap('i', '.', '.<c-g>u', opts)

-- move lines of text around <3
keymap('v', 'J', ":m '>+1<CR>gv=gv", opts)
keymap('v', 'K', ":m '<-2<CR>gv=gv", opts)
keymap('i', '<C-j>', "<esc>:m .+1<CR>==", opts)
keymap('i', '<C-k>', "<esc>:m .-2<CR>==", opts)
keymap('n', '<leader>j', ":m .+1<CR>==", opts)
keymap('n', '<leader>k', ":m .-2<CR>==", opts)

-- telescope sugar
keymap('n', '<leader>ff', "<cmd>Telescope find_files<CR>", opts)
keymap('n', '<leader>fg', "<cmd>Telescope live_grep<CR>", opts)
keymap('n', '<leader>fb', "<cmd>Telescope buffers<CR>", opts)
keymap('n', '<leader>fh', "<cmd>Telescope help_tags<CR>", opts)

-- LSP sugar
keymap('n', 'gd', ':lua vim.lsp.buf.definition()<cr>', opts)
keymap('n', 'gD', ':lua vim.lsp.buf.declaration()<cr>', opts)
keymap('n', 'gi', ':lua vim.lsp.buf.implementation()<cr>', opts)
keymap('n', 'gw', ':lua vim.lsp.buf.document_symbol()<cr>', opts)
keymap('n', 'gw', ':lua vim.lsp.buf.workspace_symbol()<cr>', opts)
keymap('n', 'gr', ':lua vim.lsp.buf.references()<cr>', opts)
keymap('n', 'gt', ':lua vim.lsp.buf.type_definition()<cr>', opts)
keymap('n', 'K', ':lua vim.lsp.buf.hover()<cr>', opts)
keymap('n', '<c-k>', ':lua vim.lsp.buf.signature_help()<cr>', opts)
keymap('n', '<leader>af', ':lua vim.lsp.buf.code_action()<cr>', opts)
keymap('n', '<leader>rn', ':lua vim.lsp.buf.rename()<cr>', opts)