perf(lsp): defer attaching client to BufEnter (#409)

CHANGELOG.md

@@ -6,6 +6,13 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Changed
+
+- LSP: Defer attaching the LSP client to `BufEnter` for a smoother experience
+  on low-end devices.
+
 ## [4.23.5] - 2024-05-24
 
 ### Fixed

ftplugin/rust.lua

@@ -46,12 +46,19 @@ end
 
 vim.g.loaded_rustaceanvim = true
 
+local bufnr = vim.api.nvim_get_current_buf()
 local auto_attach = config.server.auto_attach
 if type(auto_attach) == 'function' then
-  local bufnr = vim.api.nvim_get_current_buf()
   auto_attach = auto_attach(bufnr)
 end
 
 if auto_attach then
-  require('rustaceanvim.lsp').start()
+  -- Defer for a smoother experience on low-end devices
+  vim.api.nvim_create_autocmd('BufEnter', {
+    buffer = bufnr,
+    group = vim.api.nvim_create_augroup('RustaceanvimAttach', { clear = true }),
+    callback = function()
+      require('rustaceanvim.lsp').start()
+    end,
+  })
 end