Method _mappers_from_spec

lib/sqlalchemy/orm/mapper.py:2502–2536

given a with_polymorphic() argument, return the set of mappers it represents. Trims the list of mappers to just those represented within the given selectable, if present. This helps some more legacy-ish mappings.

(
        self, spec: Any, selectable: Optional[FromClause]
    )

        return iter(self._props.values())

    def _mappers_from_spec(
        self, spec: Any, selectable: Optional[FromClause]
    ) -> Sequence[Mapper[Any]]:
        """given a with_polymorphic() argument, return the set of mappers it
        represents.

        Trims the list of mappers to just those represented within the given
        selectable, if present. This helps some more legacy-ish mappings.

        """
        if spec == "*":
            mappers = list(self.self_and_descendants)
        elif spec:
            mapper_set: Set[Mapper[Any]] = set()
            for m in util.to_list(spec):
                m = _class_to_mapper(m)
                if not m.isa(self):
                    raise sa_exc.InvalidRequestError(
                        "%r does not inherit from %r" % (m, self)
                    )

                if selectable is None:
                    mapper_set.update(m.iterate_to_root())
                else:
                    mapper_set.add(m)
            mappers = [m for m in self.self_and_descendants if m in mapper_set]
        else:
            mappers = []

        if selectable is not None:
            tables = set(
                sql_util.find_tables(selectable, include_aliases=True)
            )
            mappers = [m for m in mappers if m.local_table in tables]
        return mappers

    def _selectable_from_mappers(
        self, mappers: Iterable[Mapper[Any]], innerjoin: bool