Function _generate_from_keys

lib/sqlalchemy/orm/strategy_options.py:2296–2357

(
    meth: Callable[..., _AbstractLoad],
    keys: Tuple[_AttrType, ...],
    chained: bool,
    kw: Any,
)

def _generate_from_keys(
    meth: Callable[..., _AbstractLoad],
    keys: Tuple[_AttrType, ...],
    chained: bool,
    kw: Any,
) -> _AbstractLoad:
    lead_element: Optional[_AbstractLoad] = None

    attr: Any
    for is_default, _keys in (True, keys[0:-1]), (False, keys[-1:]):
        for attr in _keys:
            if isinstance(attr, str):
                if attr.startswith("." + _WILDCARD_TOKEN):
                    util.warn_deprecated(
                        "The undocumented `.{WILDCARD}` format is "
                        "deprecated "
                        "and will be removed in a future version as "
                        "it is "
                        "believed to be unused. "
                        "If you have been using this functionality, "
                        "please "
                        "comment on Issue #4390 on the SQLAlchemy project "
                        "tracker.",
                        version="1.4",
                    )
                    attr = attr[1:]

                if attr == _WILDCARD_TOKEN:
                    if is_default:
                        raise sa_exc.ArgumentError(
                            "Wildcard token cannot be followed by "
                            "another entity",
                        )

                    if lead_element is None:
                        lead_element = _WildcardLoad()

                    lead_element = meth(lead_element, _DEFAULT_TOKEN, **kw)

                else:
                    raise sa_exc.ArgumentError(
                        "Strings are not accepted for attribute names in "
                        "loader options; please use class-bound "
                        "attributes directly.",
                    )
            else:
                if lead_element is None:
                    _, lead_entity, _ = _parse_attr_argument(attr)
                    lead_element = Load(lead_entity)

                if is_default:
                    if not chained:
                        lead_element = lead_element.defaultload(attr)
                    else:
                        lead_element = meth(
                            lead_element, attr, _is_chain=True, **kw
                        )
                else: