Function create_windows_process

src/mcp/os/win32/utilities.py:113–150

Creates a subprocess with Job Object support for tree termination. Spawns via anyio's open_process; event loops without async subprocess support (notably the SelectorEventLoop) raise NotImplementedError, in which case the spawn falls back to a Popen-backed FallbackProcess. Either way th

(
    command: str,
    args: list[str],
    env: dict[str, str] | None = None,
    errlog: TextIO | None = sys.stderr,
    cwd: Path | str | None = None,
)

async def create_windows_process(
    command: str,
    args: list[str],
    env: dict[str, str] | None = None,
    errlog: TextIO | None = sys.stderr,
    cwd: Path | str | None = None,
) -> Process | FallbackProcess:
    """Creates a subprocess with Job Object support for tree termination.

    Spawns via anyio's open_process; event loops without async subprocess
    support (notably the SelectorEventLoop) raise NotImplementedError, in which
    case the spawn falls back to a Popen-backed FallbackProcess. Either way the
    process is then assigned to a Job Object so its children can be terminated
    with it; children spawned before the assignment completes are not captured
    (see the inline note below).

    Returns:
        Process | FallbackProcess: The spawned process with async stdin/stdout streams.
    """
    try:
        process = await anyio.open_process(
            [command, *args],
            env=env,
            # Ensure we don't create console windows for each process
            creationflags=getattr(subprocess, "CREATE_NO_WINDOW", 0),
            stderr=errlog,
            cwd=cwd,
        )
    except NotImplementedError:
        # Windows event loops without async subprocess support (SelectorEventLoop)
        process = await _create_windows_fallback_process(command, args, env, errlog, cwd)

    # Children spawned before the assignment completes land outside the job
    # (membership is inherited at CreateProcess, never acquired retroactively);
    # if that ever bites, the fix is a CREATE_SUSPENDED spawn -> assign -> resume.
    job = _create_job_object()
    _maybe_assign_process_to_job(process, job)
    return process


async def _create_windows_fallback_process(