Refactor: use a unified log function

autoload/buf_utils.vim

@@ -11,7 +11,7 @@ function! buf_utils#GoToBuffer(count, direction) abort
   endif
   " Check the validity of buffer number.
   if index(s:GetBufNums(), a:count) == -1
-    echohl WarningMsg | echomsg 'Invalid bufnr: ' a:count | echohl None
+    call utils#Log('Invalid bufnr: ' . a:count, 'error')
     return
   endif
 

autoload/utils.vim

@@ -145,3 +145,25 @@ function! utils#Get_titlestr() abort
 
   return l:title_str
 endfunction
+
+" Log a message using certain highlight group
+function! utils#Log(msg, ...) abort
+  let l:hi = ''
+  if len(a:000) == 1
+    if a:1 ==? 'info'
+      let l:hi = 'Normal'
+    elseif a:1 ==? 'warning'
+      let l:hi = 'WarningMsg'
+    elseif a:1 ==? 'error'
+      let l:hi = 'ErrorMsg'
+    else
+      echoerr 'Unsupported log level:' a:1
+    endif
+  else
+    let l:hi = 'Normal'
+  endif
+
+  execute 'echohl' l:hi
+  unsilent echomsg a:msg
+  echohl None
+endfunction

core/autocommands.vim

@@ -42,8 +42,7 @@ augroup END
 " https://vi.stackexchange.com/a/20397/15292.
 augroup auto_read
   autocmd!
-  autocmd FileChangedShellPost * echohl WarningMsg
-        \ | echo "File changed on disk. Buffer reloaded!" | echohl None
+  autocmd FileChangedShellPost * call utils#Log("File changed on disk. Buffer reloaded!", 'warning')
   autocmd FocusGained,CursorHold * if getcmdwintype() == '' | checktime | endif
 augroup END
 

core/ui.vim

@@ -61,9 +61,7 @@ let s:colorscheme_func = printf('s:my_theme_dict.%s()', s:theme)
 if has_key(s:my_theme_dict, s:theme)
   execute 'call ' . s:colorscheme_func
 else
-  echohl WarningMsg
-  echomsg 'Invalid colorscheme function: ' s:colorscheme_func
-  echohl None
+  call utils#Log('Invalid colorscheme function: ' . s:colorscheme_func, 'error')
 endif
 "}}
 "}