experimental_lazy_setup to reduce startup time

lua/lazy-lsp/init.lua

@@ -4,8 +4,35 @@ local overrides = require("lazy-lsp.overrides")
 local helpers = require("lazy-lsp.helpers")
 
 local function setup(opts)
-  for server, server_opts in pairs(helpers.server_configs(lspconfig, servers, opts, overrides)) do
-    lspconfig[server].setup(server_opts)
+  for server, config in pairs(helpers.server_configs(lspconfig, servers, opts, overrides)) do
+    if opts.experimental_lazy_setup ~= true or not config.filetypes then
+      lspconfig[server].setup(config)
+    else
+      -- Based on https://github.com/neovim/nvim-lspconfig/blob/d67715d3b746a19e951b6b0a99663fa909bb9e64/lua/lspconfig/configs.lua#L98-L112
+      -- Decided to avoid wildcard and only register when a server explicitly specifies filetypes
+      local lsp_group = vim.api.nvim_create_augroup("lazy_lsp_setup", { clear = false })
+      local autocmd_id
+      autocmd_id = vim.api.nvim_create_autocmd("FileType", {
+        pattern = config.filetypes,
+        callback = function(opt)
+          -- We just need to setup the server once, remove autocmd so it does not run again.
+          vim.api.nvim_del_autocmd(autocmd_id)
+
+          local M = lspconfig[server]
+          M.setup(config)
+
+          -- Since we setup inside autocmd callback, we need to help trigger autostart manually.
+          -- Since lspconfig sets up its own autocmd it will handle it in the future by itself.
+          if M.autostart then
+            vim.schedule(function()
+              M.manager:try_add(opt.buf)
+            end)
+          end
+        end,
+        group = lsp_group,
+        desc = string.format("Lazily setup %s lsp server", server),
+      })
+    end
   end
 end