Permit closing window with unsaved changes using vim setting

Question

I wrote a plugin that executes a slow shell script and asynchronously shows the stdout in a popup (split) window. When I try to close my session while the popup is open, I get the message

Save changes to "popup.log"?
[Y]es, (N)o, (C)ancel

How can I automatically reject changes to this temporary buffer without rejecting changes to the files I am actually editing (as would happen with :qa!)?

Is there some buffer-local option I can set that allows the buffer to changes but specifies "this is a temporary buffer, but never ever ask me to save changes"? Seems like lots of vim plugins do this (tagbar, NERDtree, etc.) but I don't know how.

Answer 1

Is there some buffer-local option I can set that allows the buffer to changes but specifies "this is a temporary buffer, but never ever ask me to save changes"?

The most essential one is buftype=nofile. Also, :h special-buffers recommends using noswapfile (nowadays often switched off globally) and bufhidden=hide (so a buffer can be reused after :quit-ting the window; but note that ZQ and :quit! still drop it completely). As following these recommendations does not seem to hurt, you can do

setlocal buftype=nofile bufhidden=hide noswapfile