Feature/refactor quit if only left

nerdtree_plugin/vim-nerdtree-tabs.vim

@@ -318,6 +318,12 @@ fun! s:NextNormalWindow()
       continue
     endif
 
+    " skip current normal window
+    if l:i == winnr()
+      let l:i = l:i + 1
+      continue
+    endif
+
     return l:i
   endwhile
   return -1
@@ -329,8 +335,27 @@ endfun
 " Close all open buffers on entering a window if the only
 " buffer that's left is the NERDTree buffer
 fun! s:CloseIfOnlyNerdTreeLeft()
-  if exists("t:NERDTreeBufName") && bufwinnr(t:NERDTreeBufName) != -1 && winnr("$") == 1
-    q
+  " Only take action when we are in NERDTree window, and no more window
+  " with normal buffer open.
+  if exists("t:NERDTreeBufName") && bufwinnr(t:NERDTreeBufName) == winnr() && s:NextNormalWindow() == -1
+    if tabpagenr('$') == 1
+      " Before quitting Vim, delete the buffer so that the '0 mark
+      " is correctly set to the previous buffer. This avoids NERDTree
+      " buffer being the last displayed buffer if Vim fails to quit
+      " due to the last file in the argument list has not been edited
+      " yet. Also disable autocmd on this command to avoid unnecessary
+      " autocmd nesting.
+      if winnr('$') == 1
+        noautocmd bdelete
+      endif
+      " Quit as usual, we have autocmd nesting open, so this command
+      " will trigger other plugin window's quiting behavior. If we are
+      " quiting Vim, our current buffer is successfully reset to the
+      " last file buffer, no need to warry about failure.
+      quit
+    else
+      close
+    endif
   endif
 endfun
 
@@ -441,7 +466,7 @@ fun! s:LoadPlugin()
     autocmd VimEnter * call <SID>VimEnterHandler()
     autocmd TabEnter * call <SID>TabEnterHandler()
     autocmd TabLeave * call <SID>TabLeaveHandler()
-    autocmd WinEnter * call <SID>WinEnterHandler()
+    autocmd WinEnter * nested call <SID>WinEnterHandler()
     autocmd WinLeave * call <SID>WinLeaveHandler()
   augroup END