> - # Since Python 3 converts argv to wchar_t type by Py_DecodeLocale() on
> Unix,
> - # we can use os.fsencode() to get back bytes argv.
> - #
> - # https://hg.python.org/cpython/file/v3.5.1/Programs/python.c#l55
> - #
> - # On Windows, the native argv is unicode and is converted to MBCS bytes
> - # since we do enable the legacy filesystem encoding.
> if getattr(sys, 'argv', None) is not None:
> - sysargv = list(map(os.fsencode, sys.argv))
> + # On POSIX, the char** argv array is converted to Python str using
> + # Py_DecodeLocale(). The inverse of this is Py_EncodeLocale(), which
> isn't
> + # directly callable from Python code. So, we need to emulate it.
> + # Py_DecodeLocale() calls mbstowcs() and falls back to mbrtowc() with
> + # surrogateescape error handling on failure. These functions take the
> + # current system locale into account. So, the inverse operation is to
> + # .encode() using the system locale's encoding and using the
> + # surrogateescape error handler. The only tricky part here is getting
> + # the system encoding correct, since `locale.getlocale()` can return
> + # None. We fall back to the filesystem encoding if lookups via
> `locale`
> + # fail, as this seems like a reasonable thing to do.
> + #
> + # On Windows, the wchar_t **argv is passed into the interpreter
> as-is.
> + # Like POSIX, we need to emulate what Py_EncodeLocale() would do. But
> + # there's an additional wrinkle. What we really want to access is the
> + # ANSI codepage representation of the arguments, as this is what
> + # `int main()` would receive if Python 3 didn't define `int wmain()`
> + # (this is how Python 2 worked). To get that, we encode with the mbcs
> + # encoding, which will pass CP_ACP to the underlying Windows API to
> + # produce bytes.
> + if os.name == r'nt':
> + sysargv = [a.encode("mbcs", "ignore") for a in sys.argv]
On Windows, my assumption was os.fsencode() == .encode("mbcs") if
sys._enablelegacywindowsfsencoding(). So this looks good to me.
Perhaps, the "ignore" error mode would match the legacy Windows behavior.
> + else:
> + encoding = (
> + locale.getlocale()[1]
> + or locale.getdefaultlocale()[1]
> + or sys.getfilesystemencoding()
> + )
> + sysargv = [a.encode(encoding, "surrogateescape") for a in
> sys.argv]
I'm not pretty sure if the locale encoding is the encoding Py_DecodeLocale()
would use. There are many ifdefs for `__APPLE__`. The doc says use
`os.fsencode()`, but that's no longer valid (or wrong from the start)?
https://docs.python.org/3/library/sys.html#sys.argv
Something might be changed around 3.7 or 3.8. Since bytes argv handling
has been moved from `int main()` to `preconfig.c`, things could become
more dynamic. But I don't know. Just my guess.
Overall, the new code looks good, but I have no idea if that's more correct.
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