I have the autocommand described here in my .vimrc: http://superuser.com/a/669463/199803
EDIT: Copied into body of question for convenience:
function CountListedBuffers()
let cnt = 0
for nr in range(1,bufnr("$"))
if buflisted(nr) && ! empty(bufname(nr))
let cnt += 1
endif
endfor
return cnt
endfunction
function QuitIfLastBuffer()
if CountListedBuffers() == 1
:q
endif
endfunction
autocmd BufDelete * :call QuitIfLastBuffer()
Bizarrely, though, it seems that if I have exactly one listed buffer, and I try to use the :help command, the help window fails to open (or perhaps opens and is immediately closed). If I comment out that autocommand line in my .vimrc, this behavior no longer occurs.
Why is this happening, and how can I fix it? Why would :h even trigger the BufDelete event?
EDIT: setting verbosity to level 12, I can see that the BufDelete event is indeed occurring. Here's the portion of the output that looks relevant to me:
Executing BufAdd Auto commands for "*"
autocommand call <SID>BMAdd()
calling function <SNR>6_BMAdd
calling function <SNR>6_BMAdd..<SNR>6_BMFilename
calling function <SNR>6_BMAdd..<SNR>6_BMFilename..<SNR>6_BMMunge
calling function <SNR>6_BMAdd..<SNR>6_BMFilename..<SNR>6_BMMunge..<SNR>6_BMTruncName
function <SNR>6_BMAdd..<SNR>6_BMFilename..<SNR>6_BMMunge..<SNR>6_BMTruncName returning '/usr/local/share/vim/vim74/doc'
continuing in function <SNR>6_BMAdd..<SNR>6_BMFilename..<SNR>6_BMMunge
function <SNR>6_BMAdd..<SNR>6_BMFilename..<SNR>6_BMMunge returning 'help\.txt\ (4)\^I/usr/local/share/vim/vim74/doc'
continuing in function <SNR>6_BMAdd..<SNR>6_BMFilename
calling function <SNR>6_BMAdd..<SNR>6_BMFilename..<SNR>6_BMHash
function <SNR>6_BMAdd..<SNR>6_BMFilename..<SNR>6_BMHash returning #340582286
continuing in function <SNR>6_BMAdd..<SNR>6_BMFilename
function <SNR>6_BMAdd..<SNR>6_BMFilename returning #0
continuing in function <SNR>6_BMAdd
function <SNR>6_BMAdd returning #0
continuing in BufAdd Auto commands for "*"
Executing BufDelete Auto commands for "*"
autocommand :call QuitIfLastBuffer()
