"""Windows subprocess compatibility helpers. Hermes is developed on Linux / macOS and tested natively on Windows too. Several common subprocess patterns break silently-or-loudly on Windows: * ``["npm", "install", ...]`` — on Windows ``npm`` is ``npm.cmd``, a batch shim. ``subprocess.Popen(["npm", ...])`` fails with WinError 193 ("not a valid Win32 application") because CreateProcessW can't run a ``.cmd`` file without ``shell=True`` or PATHEXT resolution. * ``start_new_session=True`` — on POSIX, this maps to ``os.setsid()`` and actually detaches the child. On Windows it's silently ignored; the Windows equivalent is the ``CREATE_NEW_PROCESS_GROUP | CREATE_NO_WINDOW`` creationflags bundle, which Python only applies when you pass it explicitly. * Console-window flashes — every ``subprocess.Popen`` of a ``.exe`` on Windows spawns a cmd window briefly unless ``CREATE_NO_WINDOW`` is passed. Cosmetic but jarring for background daemons. This module centralizes the platform-branching logic so the rest of the codebase doesn't sprinkle ``if sys.platform == "win32":`` everywhere. **All helpers are no-ops on non-Windows** — calling them in Linux/macOS code paths is safe by design. That's the "do no damage on POSIX" guarantee. """ from __future__ import annotations import shutil import subprocess import sys from typing import Sequence __all__ = [ "IS_WINDOWS", "resolve_node_command", "suppress_platform_ver_console", "windows_detach_flags", "windows_detach_flags_without_breakaway", "windows_hide_flags", "windows_detach_popen_kwargs", "bounded_git_probe", ] IS_WINDOWS = sys.platform == "win32" # ----------------------------------------------------------------------------- # Node ecosystem launcher resolution # ----------------------------------------------------------------------------- def resolve_node_command(name: str, argv: Sequence[str]) -> list[str]: """Resolve a Node-ecosystem command name to an absolute-path argv. On Windows, commands like ``npm``, ``npx``, ``yarn``, ``pnpm``, ``playwright``, ``prettier`` ship as ``.cmd`` files (batch shims). ``subprocess.Popen(["npm", "install"])`` fails with WinError 193 because CreateProcessW doesn't execute batch files directly. ``shutil.which(name)`` *does* resolve ``.cmd`` via PATHEXT and returns the fully-qualified path — which CreateProcessW accepts because the extension tells Windows to route through ``cmd.exe /c``. On POSIX ``shutil.which`` also returns a fully-qualified path when found. That's a small change from bare-name resolution (the OS does its own PATH search) but functionally identical and has the side benefit of making the argv reproducible in logs. Behavior when the command is not on PATH: - On Windows: return the bare name — caller can still try with ``shell=True`` as a last resort, OR the subsequent Popen will raise FileNotFoundError with a readable error we want to surface. - On POSIX: same. Bare ``npm`` on a Linux box without npm installed fails the same way it did before this function existed. Args: name: The command name to resolve (``npm``, ``npx``, ``node`` …). argv: The remaining arguments. Must NOT include ``name`` itself — this function builds the full argv list. Returns: A list suitable for passing to subprocess.Popen/run/call. """ resolved = shutil.which(name) if resolved: return [resolved, *argv] return [name, *argv] # ----------------------------------------------------------------------------- # Detached / hidden process creation # ----------------------------------------------------------------------------- # Win32 CreationFlags — defined here rather than imported from subprocess # because CREATE_NO_WINDOW and DETACHED_PROCESS aren't guaranteed to be # present on stdlib subprocess on older Pythons or non-Windows builds. _CREATE_NEW_PROCESS_GROUP = 0x00000200 # DETACHED_PROCESS is intentionally NOT part of any flag bundle here — do not # re-add it. Two reasons (the recurring console-flash bug #54220 / #56747): # # 1. MSDN (Process Creation Flags): CREATE_NO_WINDOW "is ignored if used with # either CREATE_NEW_CONSOLE or DETACHED_PROCESS". Combining them means # DETACHED_PROCESS governs and the no-window bit is dead. # 2. A DETACHED_PROCESS child has NO console at all, so every console-subsystem # descendant it ever spawns (git, gh, cmd, node, wmic, powershell, …) must # allocate its OWN console — a visible flash per spawn, including spawns # inside third-party libraries that no per-call-site CREATE_NO_WINDOW sweep # can reach. A CREATE_NO_WINDOW child instead OWNS a hidden console that # all descendants inherit, making "no flashing windows" a property of the # one daemon launch. Root cause isolated + A/B verified on Windows 11 by # the desktop backend fix (commit aa2ae36c3f): with per-site hide flags # neutered, naive git/gh/cmd spawns don't flash under a hidden-console # parent and do flash under a console-less one. _DETACHED_PROCESS = 0x00000008 # kept for reference; must stay out of bundles _CREATE_NO_WINDOW = 0x08000000 # Escape any Win32 job object the parent process belongs to. Without this, # a detached child still inherits its parent's job object membership, and # when that parent (Electron, Tauri, Windows Terminal, the Desktop GUI's # bootstrap-installer) dies, the OS tears down the whole job — taking the # "detached" child with it. Critical for the post-update gateway watcher: # Electron spawns the Tauri updater inside its own job, the updater spawns # the watcher subprocess; without BREAKAWAY the watcher dies the instant # Electron exits, so the gateway never gets respawned after a `hermes # update` triggered from the GUI. See fix/windows-gateway-reliability. _CREATE_BREAKAWAY_FROM_JOB = 0x01000000 def windows_detach_flags() -> int: """Return Win32 creationflags that detach a child from the parent console and process group without leaving it console-less. 0 on non-Windows. Pair with ``start_new_session=False`` (default) when calling subprocess.Popen — on POSIX use ``start_new_session=True`` instead, which maps to ``os.setsid()`` in the child. Rationale: - ``CREATE_NEW_PROCESS_GROUP`` — child has its own process group so Ctrl+C in the parent console doesn't propagate. - ``CREATE_NO_WINDOW`` — the child gets its own fresh console that is never shown. This both detaches it from the parent's console lifetime (closing the launching terminal doesn't CTRL_CLOSE it) AND gives every console-subsystem descendant (git, gh, cmd, node, …) a console to inherit, so they don't allocate visible flashing ones. This deliberately replaces the old ``DETACHED_PROCESS`` approach: MSDN specifies CREATE_NO_WINDOW is *ignored* when combined with DETACHED_PROCESS, and a truly console-less daemon re-creates the per-descendant console-flash bug (#54220/#56747) at every spawn — see the note on ``_DETACHED_PROCESS`` above. - ``CREATE_BREAKAWAY_FROM_JOB`` — escape any job object the parent is in. Electron (Desktop app) and Tauri (bootstrap installer) wrap their children in job objects; without breakaway, those children die when the parent process exits even though they have their own console. This was the missing flag that made the post-update gateway respawn watcher silently die alongside the Tauri updater after the Electron Desktop's update flow finished. If a process is in a job that disallows breakaway (rare — JOB_OBJECT_LIMIT_BREAKAWAY_OK isn't set), CreateProcess returns ERROR_ACCESS_DENIED. Python surfaces that as ``PermissionError`` on the ``subprocess.Popen`` call. Callers in this codebase already wrap detached spawns in ``try/except OSError`` and fall back to a cmd.exe wrapper, so the breakaway-denied case degrades gracefully rather than crashing. """ if not IS_WINDOWS: return 0 return ( _CREATE_NEW_PROCESS_GROUP | _CREATE_NO_WINDOW | _CREATE_BREAKAWAY_FROM_JOB ) def windows_detach_flags_without_breakaway() -> int: """Same as :func:`windows_detach_flags` minus ``CREATE_BREAKAWAY_FROM_JOB``. The docstring on :func:`windows_detach_flags` notes that a process in a job which disallows breakaway (no ``JOB_OBJECT_LIMIT_BREAKAWAY_OK``) will see ``ERROR_ACCESS_DENIED`` from CreateProcess, surfacing as ``OSError`` (``PermissionError``) on the ``subprocess.Popen`` call. Callers that want to recover — by retrying without the breakaway bit — can pair the two helpers symbolically rather than coding the ``& ~0x01000000`` magic at every site: .. code-block:: python try: subprocess.Popen(argv, creationflags=windows_detach_flags(), …) except OSError: subprocess.Popen( argv, creationflags=windows_detach_flags_without_breakaway(), …, ) See ``gateway_windows.py::_spawn_detached`` for the canonical implementation of this pattern. Returns 0 on non-Windows. """ if not IS_WINDOWS: return 0 return _CREATE_NEW_PROCESS_GROUP | _CREATE_NO_WINDOW def windows_hide_flags() -> int: """Return Win32 creationflags that merely hide the child's console window without detaching the child. 0 on non-Windows. Use for short-lived console apps spawned as part of a larger operation (``taskkill``, ``where``, version probes) where we want no flash but also want to collect stdout/exit code synchronously. The difference from :func:`windows_detach_flags`: no ``CREATE_NEW_PROCESS_GROUP`` / ``CREATE_BREAKAWAY_FROM_JOB`` — the child stays in the parent's process group and job so Ctrl+C and job teardown propagate normally, as a short-lived helper wants. Stdio handles are inherited either way, so ``capture_output=True`` works with both bundles. """ if not IS_WINDOWS: return 0 return _CREATE_NO_WINDOW def suppress_platform_ver_console() -> None: """Stub out ``platform._syscmd_ver`` on Windows so it can never flash a console window. No-op on non-Windows. CPython's ``platform.win32_ver()`` — reached by ``platform.uname()``, ``platform.version()``, and ``platform.platform()`` — unconditionally shells out ``cmd /c ver`` via ``subprocess.check_output(..., shell=True)`` with no ``CREATE_NO_WINDOW``. From a windowless parent (the pythonw gateway and every kanban worker it spawns) that allocates a fresh *visible* console: one flashing ``cmd`` window per process, triggered by any dependency that merely touches ``platform.uname()`` at import time. With ``_syscmd_ver`` stubbed to return its inputs, ``win32_ver()`` hits the documented ``ValueError`` fallback and reads the version from ``sys.getwindowsversion().platform_version`` — same information, queried in-process, no subprocess, no window. Verified equivalent on CPython 3.11 (``platform()`` → ``Windows-10-10.0.xxxxx-SP0`` either way). Call early, before heavyweight imports — the flash typically happens during a dependency's import, not from Hermes' own code. """ if not IS_WINDOWS: return try: import platform if hasattr(platform, "_syscmd_ver"): def _quiet_syscmd_ver(system="", release="", version="", supported_platforms=("win32", "win16", "dos")): return system, release, version platform._syscmd_ver = _quiet_syscmd_ver except Exception: # Purely cosmetic hardening — never let it break startup. pass def windows_detach_popen_kwargs() -> dict: """Return a dict of Popen kwargs that detach a child on Windows and fall back to the POSIX equivalent (``start_new_session=True``) on Linux/macOS. Usage pattern: .. code-block:: python subprocess.Popen( argv, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL, stdin=subprocess.DEVNULL, close_fds=True, **windows_detach_popen_kwargs(), ) This replaces the unsafe-on-Windows pattern: .. code-block:: python subprocess.Popen(..., start_new_session=True) which silently fails to detach on Windows (the flag is accepted but has no effect — the child stays attached to the parent's console and dies when the console closes). """ if IS_WINDOWS: return {"creationflags": windows_detach_flags()} return {"start_new_session": True} # ----------------------------------------------------------------------------- # Bounded, fail-open git probing (Windows post-kill deadlock guard) # ----------------------------------------------------------------------------- def _kill_git_process_tree(proc: "subprocess.Popen") -> None: """Best-effort terminate *proc* and, on Windows, its descendants. ``proc.kill()`` alone only terminates the PATH-resolved ``git`` launcher; a suspended descendant ``git.exe`` can survive holding duplicates of the captured pipe handles, which keeps the pipes from reaching EOF and leaks two reader threads + the process per fired timeout. ``taskkill /T /F`` takes the whole tree down so the bounded drain that follows can actually reach EOF. All failures are swallowed — this is cleanup on an already-failing path, and the caller's contract is to fail open. ``kill()`` can raise (access denied, already reaped); an unhandled raise here would escape the caller's ``except`` handler and break that contract. The ``taskkill`` spawn itself cannot re-enter the deadlock class it fixes: it captures no pipes (DEVNULL), so its own timeout cleanup has no reader threads to join. """ try: proc.kill() except OSError: pass if IS_WINDOWS: try: subprocess.run( ["taskkill", "/T", "/F", "/PID", str(proc.pid)], stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL, stdin=subprocess.DEVNULL, timeout=2, check=False, creationflags=windows_hide_flags(), ) except Exception: pass def bounded_git_probe(argv: Sequence[str], *, timeout: float) -> str: """Run a short, throwaway ``git`` probe and return stripped stdout, or ``""`` on ANY failure (nonzero exit, timeout, spawn error, decode error). This is the shared, deadlock-safe replacement for ``subprocess.run(["git", ...], timeout=...)`` at fail-open probe call sites (``tui_gateway.git_probe.run_git``, ``agent.coding_context._git``). Why not ``subprocess.run``: on Windows, ``run()``'s post-timeout cleanup calls an *unbounded* ``communicate()`` after killing git. Killing the PATH-resolved launcher can leave a suspended descendant ``git.exe`` holding duplicates of the captured stdout/stderr handles, so the pipes never reach EOF and the reader-thread join blocks forever. On the Desktop agent-build path (``_start_agent_build → _session_info → branch() → run_git``) that turned an optional branch label into ``agent initialization timed out`` (issues #68609 / #66037). The bounded flow: an explicit ``communicate(timeout)``, then on any failure a tree-kill (see :func:`_kill_git_process_tree`) plus a bounded 1s post-kill drain; if the pipes are still held after that, they're abandoned (the orphaned reader threads are daemonic and cost nothing). The normal-path spawn contract mirrors the previous ``run`` call byte-for-byte: PIPE/PIPE/DEVNULL, ``text`` with UTF-8 ``errors="replace"`` decoding, and the hidden-window ``creationflags`` on Windows only. """ _popen_kwargs = {"creationflags": windows_hide_flags()} if IS_WINDOWS else {} try: proc = subprocess.Popen( list(argv), stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.DEVNULL, text=True, encoding="utf-8", errors="replace", **_popen_kwargs, ) except Exception: return "" try: stdout, _ = proc.communicate(timeout=timeout) except Exception: # Timeout OR any other communicate() failure (torn-down pipe, decode # error): terminate the child + descendants and drain bounded. Leaving # it running would leak the same suspended-descendant class this guards. _kill_git_process_tree(proc) try: proc.communicate(timeout=1) except Exception: pass return "" return stdout.strip() if proc.returncode == 0 else ""