Pass log-file and timeout args to daemon as proper args (#15227)

Currently, when starting the mypy daemon, we're passing the timeout and
log_file as part of the pickled options. This can cause problems if the
daemon has issues with the pickling. In this case we won't be able to
log what the problem was.
Let's pass the log_file and timeout as first class args. This also has
the advantage that we can now start the daemon in the foreground with
these args from the command line in a human writeable way.

Author: svalentin

mypy/dmypy/client.py

@@ -244,6 +244,7 @@ def __init__(self, prog: str) -> None:
 p.add_argument(
     "--timeout", metavar="TIMEOUT", type=int, help="Server shutdown timeout (in seconds)"
 )
+p.add_argument("--log-file", metavar="FILE", type=str, help="Direct daemon stdout/stderr to FILE")
 p.add_argument(
     "flags", metavar="FLAG", nargs="*", type=str, help="Regular mypy flags (precede with --)"
 )
@@ -608,21 +609,22 @@ def do_daemon(args: argparse.Namespace) -> None:
     # Lazy import so this import doesn't slow down other commands.
     from mypy.dmypy_server import Server, process_start_options
 
+    if args.log_file:
+        sys.stdout = sys.stderr = open(args.log_file, "a", buffering=1)
+        fd = sys.stdout.fileno()
+        os.dup2(fd, 2)
+        os.dup2(fd, 1)
+
     if args.options_data:
         from mypy.options import Options
 
-        options_dict, timeout, log_file = pickle.loads(base64.b64decode(args.options_data))
+        options_dict = pickle.loads(base64.b64decode(args.options_data))
         options_obj = Options()
         options = options_obj.apply_changes(options_dict)
-        if log_file:
-            sys.stdout = sys.stderr = open(log_file, "a", buffering=1)
-            fd = sys.stdout.fileno()
-            os.dup2(fd, 2)
-            os.dup2(fd, 1)
     else:
         options = process_start_options(args.flags, allow_sources=False)
-        timeout = args.timeout
-    Server(options, args.status_file, timeout=timeout).serve()
+
+    Server(options, args.status_file, timeout=args.timeout).serve()
 
 
 @action(help_parser)

mypy/dmypy_server.py

@@ -56,8 +56,12 @@ def daemonize(
         It also pickles the options to be unpickled by mypy.
         """
         command = [sys.executable, "-m", "mypy.dmypy", "--status-file", status_file, "daemon"]
-        pickled_options = pickle.dumps((options.snapshot(), timeout, log_file))
+        pickled_options = pickle.dumps(options.snapshot())
         command.append(f'--options-data="{base64.b64encode(pickled_options).decode()}"')
+        if timeout:
+            command.append(f"--timeout={timeout}")
+        if log_file:
+            command.append(f"--log-file={log_file}")
         info = STARTUPINFO()
         info.dwFlags = 0x1  # STARTF_USESHOWWINDOW aka use wShowWindow's value
         info.wShowWindow = 0  # SW_HIDE aka make the window invisible