using new bultin function

README.md

@@ -9,6 +9,8 @@ This plugin trims trailing whitespace and lines.
 
 Neovim v0.5.0+
 
+***It will soon only work with Neovim v0.7.0+.***  
+
 ## How to install
 
 ```vim

lua/trim/init.lua

@@ -1,27 +1,58 @@
 local vim = vim
 local config = require 'trim.config'
 
-local init = {}
+local M = {}
 
-init.setup = function(cfg)
-    if cfg.disable then config.disable = cfg.disable end
+local has_value = function(tbl, val)
+  for _, v in ipairs(tbl) do
+    if v == val then
+      return true
+    end
+  end
+  return false
+end
 
-    if cfg.patterns then config.patterns = cfg.patterns end
+local init_with_070_plus = function(cfg)
+  vim.api.nvim_create_augroup('TrimNvim', { clear = true })
+  vim.api.nvim_create_autocmd('BufWritePre', {
+    pattern = '*',
+    callback = function()
+      if not has_value(cfg.disable, vim.bo.filetype) then
+        require 'trim.trimmer'.trim()
+      end
+    end,
+    group = 'TrimNvim'
+  })
+end
 
-    vim.cmd [[augroup TrimNvim]]
-    vim.cmd [[  autocmd!]]
-    if #config.disable == 0 then
-        vim.cmd [[ autocmd BufWritePre * lua require'trim.trimmer'.trim() ]]
-    else
-        local disables = {}
-        for _, v in pairs(config.disable) do
-            table.insert(disables, string.format("&filetype != '%s'", v))
-        end
-        vim.cmd(string.format(
-                    "  autocmd BufWritePre * if %s | lua require'trim.trimmer'.trim()",
-                    table.concat(disables, " && ")))
+local init_without_070_plus = function(cfg)
+  vim.notify_once('trim.nvim will soon only work with nvim 0.7.0+', vim.log.levels.WARN)
+  vim.cmd [[augroup TrimNvim]]
+  vim.cmd [[  autocmd!]]
+  if #cfg.disable == 0 then
+    vim.cmd [[ autocmd BufWritePre * lua require'trim.trimmer'.trim() ]]
+  else
+    local disables = {}
+    for _, v in pairs(cfg.disable) do
+      table.insert(disables, string.format("&filetype != '%s'", v))
     end
-    vim.cmd [[augroup END]]
+    vim.cmd(string.format(
+      "  autocmd BufWritePre * if %s | lua require'trim.trimmer'.trim()",
+      table.concat(disables, " && ")))
+  end
+  vim.cmd [[augroup END]]
+end
+
+M.setup = function(cfg)
+  cfg = cfg or {}
+  if not cfg.disable then cfg.disable = config.disable end
+  if not cfg.patterns then cfg.patterns = config.patterns end
+
+  if not vim.api.nvim_create_autocmd then
+    init_without_070_plus(cfg)
+  else
+    init_with_070_plus(cfg)
+  end
 end
 
-return init
+return M