[clangd] Improve remote-index test

[kbobyrev]

Summary

Introduce a separate thread that will kill clangd-index-server after 10 seconds regardless. This helps shut down the test if the server hangs and stderr.readline() does not contain inititalizatiton message. It prevents "necessary" waiting delay for the server warm-up and only introduces additional delay if the test fails.

It also makes use of subprocess.Popen.kill() which is a portable way of handling process shutdown and avoids using signals.

clang-tools-extra/clangd/test/remote-index/pipeline_helper.py

 #!/usr/bin/env python
 #
 #===- pipeline_helper.py - Remote Index pipeline Helper *- python -------*--===#
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
 #===------------------------------------------------------------------------===#
 
 import argparse
 import os
 import subprocess
 from socket import socket
 import sys
 import time
-import signal
+import threading
+
+
+def kill_server_after_delay(server_process):
+  time.sleep(10)
+  if server_process.poll() is None:
+    server_process.kill()
 
 
 def main():
   parser = argparse.ArgumentParser()
   parser.add_argument('--input-file-name', required=True)
   parser.add_argument('--project-root', required=True)
   parser.add_argument('--index-file', required=True)
 
   args = parser.parse_args()
 
   # Grab an available port.
   with socket() as s:
     s.bind(('localhost', 0))
     server_address = 'localhost:' + str(s.getsockname()[1])
 
   index_server_process = subprocess.Popen([
       'clangd-index-server', '--server-address=' + server_address,
       args.index_file, args.project_root
   ],
                                           stderr=subprocess.PIPE)
 
+  # This will kill index_server_process if it hangs without printing init
+  # message.
+  shutdown_thread = threading.Thread(
+      target=kill_server_after_delay, args=(index_server_process,))
+  shutdown_thread.daemon = True
+  shutdown_thread.start()
+
   # Wait for the server to warm-up.
-  time.sleep(4)
   found_init_message = False
-  for line in index_server_process.stderr:
-    if b'Server listening' in line:
+  while index_server_process.poll() is None:
+    if b'Server listening' in index_server_process.stderr.readline():
       found_init_message = True
       break
 
   if not found_init_message:
     sys.exit(1)
 
   in_file = open(args.input_file_name)
 
   clangd_process = subprocess.Popen([
       'clangd', '--remote-index-address=' + server_address,
       '--project-root=' + args.project_root, '--lit-test', '--sync'
   ],
                                     stdin=in_file)
 
   clangd_process.wait()
-  os.kill(index_server_process.pid, signal.SIGINT)
+  index_server_process.kill()
 
 
 if __name__ == '__main__':
   main()