torch/fx/immutable_collections.py

from typing import Any, Dict, Tuple, List

from ._compatibility import compatibility
from torch.utils._pytree import Context, _register_pytree_node

__all__ = ["immutable_list", "immutable_dict"]

_help_mutation = """\
If you are attempting to modify the kwargs or args of a torch.fx.Node object,
instead create a new copy of it and assign the copy to the node:
    new_args = ... # copy and mutate args
    node.args = new_args
"""

def _no_mutation(self, *args, **kwargs):
    raise NotImplementedError(f"'{type(self).__name__}' object does not support mutation. {_help_mutation}")

def _create_immutable_container(base, mutable_functions):
    container = type('immutable_' + base.__name__, (base,), {})
    for attr in mutable_functions:
        setattr(container, attr, _no_mutation)
    return container

immutable_list = _create_immutable_container(list,
                                             ['__delitem__', '__iadd__', '__imul__', '__setitem__', 'append',
                                              'clear', 'extend', 'insert', 'pop', 'remove'])
immutable_list.__reduce__ = lambda self: (immutable_list, (tuple(iter(self)),))
immutable_list.__hash__ = lambda self: hash(tuple(self))

compatibility(is_backward_compatible=True)(immutable_list)

immutable_dict = _create_immutable_container(dict, ['__delitem__', '__setitem__', 'clear', 'pop', 'popitem', 'update'])
immutable_dict.__reduce__ = lambda self: (immutable_dict, (iter(self.items()),))
immutable_dict.__hash__ = lambda self: hash(tuple(self.items()))
compatibility(is_backward_compatible=True)(immutable_dict)


# Register immutable collections for PyTree operations

def _immutable_dict_flatten(d: Dict[Any, Any]) -> Tuple[List[Any], Context]:
    return list(d.values()), list(d.keys())

def _immutable_dict_unflatten(values: List[Any], context: Context) -> Dict[Any, Any]:
    return immutable_dict(dict(zip(context, values)))

def _immutable_list_flatten(d: List[Any]) -> Tuple[List[Any], Context]:
    return d, None

def _immutable_list_unflatten(values: List[Any], context: Context) -> List[Any]:
    return immutable_list(values)


_register_pytree_node(immutable_dict, _immutable_dict_flatten, _immutable_dict_unflatten)
_register_pytree_node(immutable_list, _immutable_list_flatten, _immutable_list_unflatten)