health.vim: check shada file neovim#10327

closes neovim#1202

runtime/autoload/health/nvim.vim

@@ -8,7 +8,7 @@ function! s:check_config() abort
   if !filereadable(vimrc)
     let ok = v:false
     let has_vim = filereadable(expand('~/.vimrc'))
-    call health#report_warn('Missing user config file: '.vimrc,
+    call health#report_warn((-1 == getfsize(vimrc) ? 'Missing' : 'Unreadable').' user config file: '.vimrc,
           \[ has_vim ? ':help nvim-from-vim' : ':help init.vim' ])
   endif
 
@@ -41,6 +41,12 @@ function! s:check_config() abort
           \   'Check `:verbose set paste?` to see if a plugin or script set the option.', ])
   endif
 
+  let shadafile = (empty(&shadafile) || &shadafile ==# 'NONE') ? stdpath('data').'/shada/main.shada' : &shadafile
+  if !empty(shadafile) && (!filereadable(shadafile) || !filewritable(shadafile))
+    let ok = v:false
+    call health#report_error('shada file is not '.(filereadable(shadafile) ? 'writeable' : 'readable').":\n".shadafile)
+  endif
+
   if ok
     call health#report_ok('no issues found')
   endif