Function daemonize

mypy/dmypy_server.py:46–73

Create the daemon process via "dmypy daemon" and pass options via command line When creating the daemon grandchild, we create it in a new console, which is started hidden. We cannot use DETACHED_PROCESS since it will cause console windows to pop up when starting. See

(
        options: Options, status_file: str, timeout: int | None = None, log_file: str | None = None
    )

    from subprocess import STARTUPINFO

    def daemonize(
        options: Options, status_file: str, timeout: int | None = None, log_file: str | None = None
    ) -> int:
        """Create the daemon process via "dmypy daemon" and pass options via command line

        When creating the daemon grandchild, we create it in a new console, which is
        started hidden. We cannot use DETACHED_PROCESS since it will cause console windows
        to pop up when starting. See
        https://github.com/python/cpython/pull/4150#issuecomment-340215696
        for more on why we can't have nice things.

        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())
        command.append(f'--options-data="{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
        try:
            subprocess.Popen(command, creationflags=0x10, startupinfo=info)  # CREATE_NEW_CONSOLE
            return 0
        except subprocess.CalledProcessError as e:
            return e.returncode

else: