my-nvim-setup/lua/plugins/lspconfig.lua

local present1, lspconfig = pcall(require, "lspconfig")
local present2, lspinstall = pcall(require, "lspinstall")
if not (present1 or present2) then
    return
end

local function on_attach(client, bufnr)
    vim.api.nvim_buf_set_option(bufnr, "omnifunc", "v:lua.vim.lsp.omnifunc")

    local opts = {noremap = true, silent = true}

    local function buf_set_keymap(...)
        vim.api.nvim_buf_set_keymap(bufnr, ...)
    end

    -- Mappings.

    buf_set_keymap("n", "gD", "<Cmd>lua vim.lsp.buf.declaration()<CR>", opts)
    buf_set_keymap("n", "gd", "<Cmd>lua vim.lsp.buf.definition()<CR>", opts)
    buf_set_keymap("n", "K", "<Cmd>lua vim.lsp.buf.hover()<CR>", opts)
    buf_set_keymap("n", "gi", "<cmd>lua vim.lsp.buf.implementation()<CR>", opts)
    buf_set_keymap("n", "<C-k>", "<cmd>lua vim.lsp.buf.signature_help()<CR>", opts)
    buf_set_keymap("n", "<space>wa", "<cmd>lua vim.lsp.buf.add_workspace_folder()<CR>", opts)
    buf_set_keymap("n", "<space>wr", "<cmd>lua vim.lsp.buf.remove_workspace_folder()<CR>", opts)
    buf_set_keymap("n", "<space>wl", "<cmd>lua print(vim.inspect(vim.lsp.buf.list_workspace_folders()))<CR>", opts)
    buf_set_keymap("n", "<space>D", "<cmd>lua vim.lsp.buf.type_definition()<CR>", opts)
    buf_set_keymap("n", "<space>rn", "<cmd>lua vim.lsp.buf.rename()<CR>", opts)
    buf_set_keymap("n", "gr", "<cmd>lua vim.lsp.buf.references()<CR>", opts)
    buf_set_keymap("n", "<space>e", "<cmd>lua vim.lsp.diagnostic.show_line_diagnostics()<CR>", opts)
    buf_set_keymap("n", "[d", "<cmd>lua vim.lsp.diagnostic.goto_prev()<CR>", opts)
    buf_set_keymap("n", "]d", "<cmd>lua vim.lsp.diagnostic.goto_next()<CR>", opts)
    buf_set_keymap("n", "<space>q", "<cmd>lua vim.lsp.diagnostic.set_loclist()<CR>", opts)

    -- Set some keybinds conditional on server capabilities
    if client.resolved_capabilities.document_formatting then
        buf_set_keymap("n", "<space>f", "<cmd>lua vim.lsp.buf.formatting()<CR>", opts)
    elseif client.resolved_capabilities.document_range_formatting then
        buf_set_keymap("n", "<space>f", "<cmd>lua vim.lsp.buf.range_formatting()<CR>", opts)
    end
end

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

-- lspInstall + lspconfig stuff

local function setup_servers()
    lspinstall.setup()
    local servers = lspinstall.installed_servers()

    for _, lang in pairs(servers) do
        if lang ~= "lua" then
            lspconfig[lang].setup {
                on_attach = on_attach,
                capabilities = capabilities,
                root_dir = vim.loop.cwd
            }
        elseif lang == "lua" then
            lspconfig[lang].setup {
                root_dir = vim.loop.cwd,
                settings = {
                    Lua = {
                        diagnostics = {
                            globals = {"vim"}
                        },
                        workspace = {
                            library = {
                                [vim.fn.expand("$VIMRUNTIME/lua")] = true,
                                [vim.fn.expand("$VIMRUNTIME/lua/vim/lsp")] = true
                            },
                            maxPreload = 100000,
                            preloadFileSize = 10000
                        },
                        telemetry = {
                            enable = false
                        }
                    }
                }
            }
        end
    end
end

setup_servers()

-- Automatically reload after `:LspInstall <server>` so we don't have to restart neovim
lspinstall.post_install_hook = function()
    setup_servers() -- reload installed servers
    vim.cmd("bufdo e") -- triggers FileType autocmd that starts the server
end

-- replace the default lsp diagnostic letters with prettier symbols
vim.fn.sign_define("LspDiagnosticsSignError", {text = "", numhl = "LspDiagnosticsDefaultError"})
vim.fn.sign_define("LspDiagnosticsSignWarning", {text = "", numhl = "LspDiagnosticsDefaultWarning"})
vim.fn.sign_define("LspDiagnosticsSignInformation", {text = "", numhl = "LspDiagnosticsDefaultInformation"})
vim.fn.sign_define("LspDiagnosticsSignHint", {text = "", numhl = "LspDiagnosticsDefaultHint"})