perf: don't run ftplugin/rust.lua more than once per buffer

CHANGELOG.md

@@ -6,15 +6,20 @@ 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]
+## [4.0.1] - 2024-01-27
 
 ### Fixed
 
-- LSP: Only setup `vim.lsp.commands` for rust-analyzer on the first
-  initialization.
 - LSP: Fix resetting client state on `:RustAnalyzer stop`
   if only one client is attached.
 
+### Performance
+
+- Only setup `vim.lsp.commands` for rust-analyzer on the first
+  initialization.
+- Don't run `ftplugin/rust.lua` more than once on the same
+  buffer.
+
 ## [4.0.0] - 2024-01-25
 
 ### BREAKING CHANGES

ftplugin/rust.lua

@@ -1,3 +1,8 @@
+local bufnr = vim.api.nvim_get_current_buf()
+if vim.b[bufnr].did_rustaceanvim_ftplugin then
+  return
+end
+
 ---@type RustaceanConfig
 local config = require('rustaceanvim.config.internal')
 local types = require('rustaceanvim.types.internal')
@@ -42,3 +47,5 @@ if not auto_attach then
 end
 
 lsp.start()
+
+vim.b[bufnr].did_rustaceanvim_ftplugin = true