nvimrc/lua/zak/configs/lsp.lua

local on_attach = function(_, bufnr)
  local nmap = function(keys, func, desc)
    if desc then
      desc = 'LSP: ' .. desc
    end

    vim.keymap.set('n', keys, func, { buffer = bufnr, desc = desc })
  end

  nmap('<leader>rn', vim.lsp.buf.rename, '[R]e[n]ame')
  nmap('<leader>ca', vim.lsp.buf.code_action, '[C]ode [A]ction')

  nmap('gd', vim.lsp.buf.definition, '[G]oto [D]efinition')
  nmap('gr', require('telescope.builtin').lsp_references, '[G]oto [R]eferences')
  nmap('gI', vim.lsp.buf.implementation, '[G]oto [I]mplementation')
  nmap('<leader>D', vim.lsp.buf.type_definition, 'Type [D]efinition')
  nmap('<leader>ds', require('telescope.builtin').lsp_document_symbols, '[D]ocument [S]ymbols')
  nmap('<leader>ws', require('telescope.builtin').lsp_dynamic_workspace_symbols, '[W]orkspace [S]ymbols')

  -- See `:help K` for why this keymap
  nmap('K', vim.lsp.buf.hover, 'Hover Documentation')
  nmap('<C-k>', vim.lsp.buf.signature_help, 'Signature Documentation')

  -- Lesser used LSP functionality
  nmap('gD', vim.lsp.buf.declaration, '[G]oto [D]eclaration')
  nmap('<leader>wa', vim.lsp.buf.add_workspace_folder, '[W]orkspace [A]dd Folder')
  nmap('<leader>wr', vim.lsp.buf.remove_workspace_folder, '[W]orkspace [R]emove Folder')
  nmap('<leader>wl', function()
    print(vim.inspect(vim.lsp.buf.list_workspace_folders()))
  end, '[W]orkspace [L]ist Folders')

  -- Create a command `:Format` local to the LSP buffer
  vim.api.nvim_buf_create_user_command(bufnr, 'Format', function(_)
    vim.lsp.buf.format()
  end, { desc = 'Format current buffer with LSP' })
end

local servers = {
  lua_ls = {
    Lua = {
      workspace = { checkThirdParty = false },
      telemetry = { enable = false },
    },
  },
  ocamllsp = {}
}

-- Setup neovim lua configuration
require('neodev').setup()

-- nvim-cmp supports additional completion capabilities, so broadcast that to servers
local capabilities = vim.lsp.protocol.make_client_capabilities()
capabilities = require('cmp_nvim_lsp').default_capabilities(capabilities)

-- Ensure the servers above are installed
local mason_lspconfig = require 'mason-lspconfig'

mason_lspconfig.setup {
  ensure_installed = vim.tbl_keys(servers),
}

mason_lspconfig.setup_handlers {
  function(server_name)
    require('lspconfig')[server_name].setup {
      capabilities = capabilities,
      on_attach = on_attach,
      settings = servers[server_name],
    }
  end,
}

local lsp = require('lspconfig')

-- Diagnostic symbols in the sign column (gutter)
local signs = {
    Error = " ",
    Warn = " ",
    Info = " ",
    Hint = " "
}
for type, icon in pairs(signs) do
    local hl = "DiagnosticSign" .. type
    vim.fn.sign_define(hl, { text = icon, texthl = hl, numhl = "" })
end

vim.diagnostic.config({
    virtual_text = {
        prefix = "●"
    },
    signs = true,
    update_in_insert = true,
    underline = false,
    severity_sort = true,
    float = {
        border = "rounded",
        source = "always",
        header = "",
        prefix = "",
    },
})

vim.lsp.handlers["textDocument/publishDiagnostics"] = vim.lsp.with(
    vim.lsp.diagnostic.on_publish_diagnostics, {
        underline = false,
        update_in_insert = false,
        virtual_text = { spacing = 4, prefix = "●" },
        severity_sort = true,
    })

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"}
)

vim.cmd [[
" make hover window"s background transparent
highlight! link FloatBorder Normal
highlight! link NormalFloat Normal
]]

-- nvim-cmp setup
local cmp = require 'cmp'
local luasnip = require 'luasnip'

luasnip.config.setup {}

local has_words_before = function()
    local line, col = unpack(vim.api.nvim_win_get_cursor(0))
    return col ~= 0 and vim.api.nvim_buf_get_lines(0, line - 1, line, true)[1]:sub(col, col):match("%s") == nil
end

local cmp_kinds = {
    Text = "",
    Method = "",
    Function = "",
    Constructor = "",
    Field = "",
    Variable = "",
    Class = "ﴯ",
    Interface = "",
    Module = "",
    Property = "ﰠ",
    Unit = "",
    Value = "λ",
    Enum = "",
    Keyword = "",
    Snippet = "",
    Color = "",
    File = "",
    Reference = "",
    Folder = "",
    EnumMember = "",
    Constant = "",
    Struct = "",
    Event = "",
    Operator = "",
    TypeParameter = ""
}

cmp.setup {
  snippet = {
    expand = function(args)
      luasnip.lsp_expand(args.body)
    end,
  },
  window = {
        completion = {
            winhighlight = "Normal:Pmenu,FloatBorder:Pmenu,Search:None",
        },
        documentation = {
            border = { "╭", "─", "╮", "│", "╯", "─", "╰", "│" },
        },
    },
  mapping = cmp.mapping.preset.insert {
    ['<C-n>'] = cmp.mapping.select_next_item(),
    ['<C-p>'] = cmp.mapping.select_prev_item(),
    ['<C-d>'] = cmp.mapping.scroll_docs(-4),
    ['<C-f>'] = cmp.mapping.scroll_docs(4),
    ['<C-Space>'] = cmp.mapping.complete {},
    ['<C-m>'] = cmp.mapping.confirm {
      behavior = cmp.ConfirmBehavior.Replace,
      select = false,
    },
    ['<Tab>'] = cmp.mapping(function(fallback)
      if cmp.visible() then
        cmp.select_next_item()
      elseif luasnip.expand_or_jumpable() then
        luasnip.expand_or_jump()
      else
        fallback()
      end
    end, { 'i', 's' }),
    ['<S-Tab>'] = cmp.mapping(function(fallback)
      if cmp.visible() then
        cmp.select_prev_item()
      elseif luasnip.jumpable(-1) then
        luasnip.jump(-1)
      else
        fallback()
      end
    end, { 'i', 's' }),
  },
  sources = {
    { name = 'nvim_lsp' },
    { name = 'luasnip' },
    { name = 'buffer' },
    option = {
      get_bufnrs = function()
        local bufs = {}
        for _, win in ipairs(vim.api.nvim_list_wins()) do
            bufs[vim.api.nvim_win_get_buf(win)] = true
        end
        return vim.tbl_keys(bufs)
      end
    }
  },
  formatting = {
    fields = { "kind", "abbr", "menu" },
    format = function(entry, vim_item)
        vim_item.kind = cmp_kinds[vim_item.kind] or ""
        local lsp_icon = "🅻"
        if lsp ~= nil and lsp.ocamllsp ~= nil then
            lsp_icon = "🐫"
        end
        vim_item.menu = ({
            buffer = "🅱",
            nvim_lsp = lsp_icon,
            luasnip = "㊊"
        })[entry.source.name]
        return vim_item
    end,
  }
}