refactor: make executable check async

executable is sync version when one of formatter is
not executable it will cause nvim block, make executable
check async and move to FileType callback we don't need
check all when config. just lazied check when need.

Author: glepnir

lua/guard/events.lua

@@ -175,20 +175,38 @@ end
 ---@param ft string
 ---@param formatters FmtConfig[]
 function M.fmt_on_filetype(ft, formatters)
-  -- check if all cmds executable before registering formatter
-  iter(formatters):any(function(config)
-    if type(config) == 'table' and config.cmd and vim.fn.executable(config.cmd) ~= 1 then
-      report_error(config.cmd .. ' not executable')
-      return false
-    end
-    return true
-  end)
-
   au('FileType', {
     group = M.group,
     pattern = ft,
     callback = function(args)
-      M.try_attach_fmt_to_buf(args.buf)
+      local ok = true
+      local co
+      co = coroutine.create(function()
+        local it = iter(formatters)
+        while true do
+          local config = it:next()
+          if not config then
+            break
+          end
+          if type(config) == 'table' and config.cmd then
+            vim.uv.fs_stat(vim.fn.exepath(config.cmd), function(err, stat)
+              if err or not stat or stat.type ~= 'file' then
+                ok = false
+              end
+              coroutine.resume(co)
+            end)
+            coroutine.yield()
+            if not ok then
+              vim.schedule(function()
+                report_error(('%s not executable'):format(config.cmd))
+                api.nvim_del_autocmd(args.id)
+              end)
+            end
+          end
+        end
+        M.try_attach_fmt_to_buf(args.buf)
+      end)
+      coroutine.resume(co)
     end,
     desc = 'guard',
   })