def mode_to_octal_str()

in antlir/compiler/items/stat_options.py [0:0]

• 34 lines of code
• 10 McCabe index (conditional complexity)

def mode_to_octal_str(mode: Mode) -> str:
    """Converts an instance of `Mode` to an octal string. If `mode` is a string,
    it's expected to be in the chmod symbolic string format with the following
    added restrictions:

    - Only append ("+") actions are supported, as we always apply the changes on
      top of mode 0.
    - No "X" is supported, as this conversion must be compatible with `stat(1)`.
    """
    # `mode` can be the empty string
    mode = mode or 0
    if isinstance(mode, int):
        return f"{mode:04o}"
    assert (
        "-" not in mode and "=" not in mode
    ), "Only append actions ('+') are supported in mode strings"
    result = 0
    for directive in mode.split(","):
        try:
            classes, perms = directive.split("+")
        except ValueError:
            raise ValueError(
                "Expected directive in the form [classes...]+[perms...] "
                f"for {mode}"
            )
        # Support empty classes
        classes = classes or ["a"]
        for stat_cls in classes:
            stat_cls_fn = _STAT_CLASSES.get(stat_cls, None)
            assert stat_cls_fn, (
                f'Only classes of "{",".join(_STAT_CLASSES.keys())}" '
                "are supported when setting mode"
            )
            for perm in perms:
                if perm in {"s", "t"}:
                    result |= _STAT_EXTRA_PERMS.get((perm, stat_cls), 0) << 9
                else:
                    mask = _STAT_PERMS.get(perm, None)
                    assert mask, (
                        f'Only permissions of "{",".join(_STAT_PERMS.keys())}" '
                        "are supported when setting mode"
                    )
                    result |= stat_cls_fn(mask)
    return f"{result:04o}"