Update

ftplugin/kotlin.vim

@@ -2,8 +2,29 @@ if polyglot#init#is_disabled(expand('<sfile>:p'), 'kotlin', 'ftplugin/kotlin.vim
   finish
 endif
 
+" Vim filetype plugin file
+" Language:     Kotlin
+" Maintainer:   Alexander Udalov
+" URL:          https://github.com/udalov/kotlin-vim
+" Last Change:  7 November 2021
+
 if exists('b:did_ftplugin') | finish | endif
 let b:did_ftplugin = 1
 
+let s:save_cpo = &cpo
+set cpo&vim
+
 setlocal comments=sO:*\ -,mO:*\ \ ,exO:*/,s1:/*,mb:*,ex:*/,://
 setlocal commentstring=//\ %s
+
+setlocal formatoptions-=t formatoptions+=croqnl
+silent! setlocal formatoptions+=j
+
+setlocal includeexpr=substitute(v:fname,'\\.','/','g')
+setlocal suffixesadd=.kt
+
+let b:undo_ftplugin = "setlocal comments< commentstring< ".
+    \ "formatoptions< includeexpr< suffixesadd<"
+
+let &cpo = s:save_cpo
+unlet s:save_cpo