Function make_safe_parse_float

Lib/tomllib/_parser.py:740–758

A decorator to make `parse_float` safe. `parse_float` must not return dicts or lists, because these types would be mixed with parsed TOML tables and arrays, thus confusing the parser. The returned decorated callable raises `ValueError` instead of returning illegal types.

(parse_float: ParseFloat)

def make_safe_parse_float(parse_float: ParseFloat) -> ParseFloat:
    """A decorator to make `parse_float` safe.

    `parse_float` must not return dicts or lists, because these types
    would be mixed with parsed TOML tables and arrays, thus confusing
    the parser. The returned decorated callable raises `ValueError`
    instead of returning illegal types.
    """
    # The default `float` callable never returns illegal types. Optimize it.
    if parse_float is float:
        return float

    def safe_parse_float(float_str: str) -> Any:
        float_value = parse_float(float_str)
        if isinstance(float_value, (dict, list)):
            raise ValueError("parse_float must not return dicts or lists")
        return float_value

    return safe_parse_float