Abort python processes on Vim exit

You'd think a scripting language could handle portably checking if a pid
is still running but no.

autoload/nrepl/fireplace_connection.vim

@@ -164,12 +164,16 @@ function! s:extract_last_stacktrace(nrepl) abort
     return stacktrace
 endfunction
 
+let s:keepalive = tempname()
+call writefile([getpid()], s:keepalive)
+
 function! s:nrepl_dispatch(command, ...) dict abort
   let in = 'python'
         \ . ' ' . s:shellesc(s:python_dir.'/nrepl_fireplace.py')
         \ . ' ' . s:shellesc(a:command)
         \ . ' ' . s:shellesc(self.host)
         \ . ' ' . s:shellesc(self.port)
+        \ . ' ' . s:shellesc(s:keepalive)
         \ . ' ' . join(map(copy(a:000), 's:shellesc(v:val)'), ' ')
   let out = system(in)
   if !v:shell_error
@@ -228,7 +232,7 @@ def fireplace_check():
 
 def fireplace_repl_dispatch(command, *args):
   try:
-    fireplace_let('out', nrepl_fireplace.dispatch(command, vim.eval('self.host'), vim.eval('self.port'), fireplace_check, *args))
+    fireplace_let('out', nrepl_fireplace.dispatch(command, vim.eval('self.host'), vim.eval('self.port'), fireplace_check, None, *args))
   except Exception, e:
     fireplace_let('err', str(e))
 EOF

python/nrepl_fireplace.py

@@ -59,14 +59,20 @@ def bdecode(f, char=None):
 
 
 class Connection:
-  def __init__(self, host, port, poll=noop):
-    self.poll = poll
+  def __init__(self, host, port, custom_poll=noop, keepalive_file=None):
+    self.custom_poll = custom_poll
+    self.keepalive_file = keepalive_file
     s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
     s.settimeout(8)
     s.connect((host, int(port)))
     s.setblocking(1)
     self.socket = s
 
+  def poll(self):
+    self.custom_poll()
+    if self.keepalive_file and not os.path.exists(self.keepalive_file):
+      exit(0)
+
   def close(self):
     return self.socket.close()
 
@@ -91,16 +97,16 @@ class Connection:
       if 'status' in responses[-1] and 'done' in responses[-1]['status']:
         return responses
 
-def dispatch(command, host, port, poll, *args):
-  conn = Connection(host, port, poll)
+def dispatch(command, host, port, poll, keepalive, *args):
+  conn = Connection(host, port, poll, keepalive)
   try:
     return getattr(conn, command)(*args)
   finally:
     conn.close()
 
-def main(command, host, port, *args):
+def main(command, host, port, keepalive, *args):
   try:
-    sys.stdout.write(vim_encode(dispatch(command, host, port, noop, *args)))
+    sys.stdout.write(vim_encode(dispatch(command, host, port, noop, keepalive, *args)))
   except Exception, e:
     print(e)
     exit(1)