Function _windowsconsoleio_workaround

src/_pytest/capture.py:100–152

Workaround for Windows Unicode console handling. Python 3.6 implemented Unicode console handling for Windows. This works by reading/writing to the raw console handle using ``{Read,Write}ConsoleW``. The problem is that we are going to ``dup2`` over the stdio file descriptors whe

(stream: TextIO)

def _windowsconsoleio_workaround(stream: TextIO) -> None:
    """Workaround for Windows Unicode console handling.

    Python 3.6 implemented Unicode console handling for Windows. This works
    by reading/writing to the raw console handle using
    ``{Read,Write}ConsoleW``.

    The problem is that we are going to ``dup2`` over the stdio file
    descriptors when doing ``FDCapture`` and this will ``CloseHandle`` the
    handles used by Python to write to the console. Though there is still some
    weirdness and the console handle seems to only be closed randomly and not
    on the first call to ``CloseHandle``, or maybe it gets reopened with the
    same handle value when we suspend capturing.

    The workaround in this case will reopen stdio with a different fd which
    also means a different handle by replicating the logic in
    "Py_lifecycle.c:initstdio/create_stdio".

    :param stream:
        In practice ``sys.stdout`` or ``sys.stderr``, but given
        here as parameter for unittesting purposes.

    See https://github.com/pytest-dev/py/issues/103.
    """
    if not sys.platform.startswith("win32") or hasattr(sys, "pypy_version_info"):
        return

    # Bail out if ``stream`` doesn't seem like a proper ``io`` stream (#2666).
    if not hasattr(stream, "buffer"):  # type: ignore[unreachable,unused-ignore]
        return

    raw_stdout = stream.buffer.raw if hasattr(stream.buffer, "raw") else stream.buffer

    if not isinstance(raw_stdout, io._WindowsConsoleIO):  # type: ignore[attr-defined,unused-ignore]
        return

    def _reopen_stdio(f, mode):
        if not hasattr(stream.buffer, "raw") and mode[0] == "w":
            buffering = 0
        else:
            buffering = -1

        return io.TextIOWrapper(
            open(os.dup(f.fileno()), mode, buffering),
            f.encoding,
            f.errors,
            f.newlines,
            f.line_buffering,
        )

    sys.stdin = _reopen_stdio(sys.stdin, "rb")
    sys.stdout = _reopen_stdio(sys.stdout, "wb")
    sys.stderr = _reopen_stdio(sys.stderr, "wb")


@hookimpl(wrapper=True)