from copy import copy from inspect import isclass, signature, Signature, getmodule from typing import ( Annotated, AnyStr, Literal, NamedTuple, NewType, Optional, Protocol, TypeGuard, Union, get_args, get_origin, is_typeddict, ) from collections.abc import Callable, Sequence import ast import builtins import collections import dataclasses import operator import sys import typing import warnings from functools import cached_property from dataclasses import dataclass, field from types import MethodDescriptorType, ModuleType, MethodType from IPython.utils.decorators import undoc import types from typing import Self, LiteralString, get_type_hints if sys.version_info < (3, 12): from typing_extensions import TypeAliasType else: from typing import TypeAliasType @undoc class HasGetItem(Protocol): def __getitem__(self, key) -> None: ... @undoc class InstancesHaveGetItem(Protocol): def __call__(self, *args, **kwargs) -> HasGetItem: ... @undoc class HasGetAttr(Protocol): def __getattr__(self, key) -> None: ... @undoc class DoesNotHaveGetAttr(Protocol): pass # By default `__getattr__` is not explicitly implemented on most objects MayHaveGetattr = Union[HasGetAttr, DoesNotHaveGetAttr] def _unbind_method(func: Callable) -> Union[Callable, None]: """Get unbound method for given bound method. Returns None if cannot get unbound method, or method is already unbound. """ owner = getattr(func, "__self__", None) owner_class = type(owner) name = getattr(func, "__name__", None) instance_dict_overrides = getattr(owner, "__dict__", None) if ( owner is not None and name and ( not instance_dict_overrides or (instance_dict_overrides and name not in instance_dict_overrides) ) ): return getattr(owner_class, name) return None @undoc @dataclass class EvaluationPolicy: """Definition of evaluation policy.""" allow_locals_access: bool = False allow_globals_access: bool = False allow_item_access: bool = False allow_attr_access: bool = False allow_builtins_access: bool = False allow_all_operations: bool = False allow_any_calls: bool = False allow_auto_import: bool = False allowed_calls: set[Callable] = field(default_factory=set) def can_get_item(self, value, item): return self.allow_item_access def can_get_attr(self, value, attr): return self.allow_attr_access def can_operate(self, dunders: tuple[str, ...], a, b=None): if self.allow_all_operations: return True def can_call(self, func): if self.allow_any_calls: return True if func in self.allowed_calls: return True owner_method = _unbind_method(func) if owner_method and owner_method in self.allowed_calls: return True def _get_external(module_name: str, access_path: Sequence[str]): """Get value from external module given a dotted access path. Only gets value if the module is already imported. Raises: * `KeyError` if module is removed not found, and * `AttributeError` if access path does not match an exported object """ try: member_type = sys.modules[module_name] # standard module for attr in access_path: member_type = getattr(member_type, attr) return member_type except (KeyError, AttributeError): # handle modules in namespace packages module_path = ".".join([module_name, *access_path]) if module_path in sys.modules: return sys.modules[module_path] raise def _has_original_dunder_external( value, module_name: str, access_path: Sequence[str], method_name: str, ): if module_name not in sys.modules: full_module_path = ".".join([module_name, *access_path]) if full_module_path not in sys.modules: # LBYLB as it is faster return False try: member_type = _get_external(module_name, access_path) value_type = type(value) if type(value) == member_type: return True if isinstance(member_type, ModuleType): value_module = getmodule(value_type) if not value_module or not value_module.__name__: return False if ( value_module.__name__ == member_type.__name__ or value_module.__name__.startswith(member_type.__name__ + ".") ): return True if method_name == "__getattribute__": # we have to short-circuit here due to an unresolved issue in # `isinstance` implementation: https://bugs.python.org/issue32683 return False if not isinstance(member_type, ModuleType) and isinstance(value, member_type): method = getattr(value_type, method_name, None) member_method = getattr(member_type, method_name, None) if member_method == method: return True if isinstance(member_type, ModuleType): method = getattr(value_type, method_name, None) for base_class in value_type.__mro__[1:]: base_module = getmodule(base_class) if base_module and ( base_module.__name__ == member_type.__name__ or base_module.__name__.startswith(member_type.__name__ + ".") ): # Check if the method comes from this trusted base class base_method = getattr(base_class, method_name, None) if base_method is not None and base_method == method: return True except (AttributeError, KeyError): return False def _has_original_dunder( value, allowed_types, allowed_methods, allowed_external, method_name ): # note: Python ignores `__getattr__`/`__getitem__` on instances, # we only need to check at class level value_type = type(value) # strict type check passes → no need to check method if value_type in allowed_types: return True method = getattr(value_type, method_name, None) if method is None: return None if method in allowed_methods: return True for module_name, *access_path in allowed_external: if _has_original_dunder_external(value, module_name, access_path, method_name): return True return False def _coerce_path_to_tuples( allow_list: set[tuple[str, ...] | str], ) -> set[tuple[str, ...]]: """Replace dotted paths on the provided allow-list with tuples.""" return { path if isinstance(path, tuple) else tuple(path.split(".")) for path in allow_list } @undoc @dataclass class SelectivePolicy(EvaluationPolicy): allowed_getitem: set[InstancesHaveGetItem] = field(default_factory=set) allowed_getitem_external: set[tuple[str, ...] | str] = field(default_factory=set) allowed_getattr: set[MayHaveGetattr] = field(default_factory=set) allowed_getattr_external: set[tuple[str, ...] | str] = field(default_factory=set) allowed_operations: set = field(default_factory=set) allowed_operations_external: set[tuple[str, ...] | str] = field(default_factory=set) allow_getitem_on_types: bool = field(default_factory=bool) _operation_methods_cache: dict[str, set[Callable]] = field( default_factory=dict, init=False ) def can_get_attr(self, value, attr): allowed_getattr_external = _coerce_path_to_tuples(self.allowed_getattr_external) has_original_attribute = _has_original_dunder( value, allowed_types=self.allowed_getattr, allowed_methods=self._getattribute_methods, allowed_external=allowed_getattr_external, method_name="__getattribute__", ) has_original_attr = _has_original_dunder( value, allowed_types=self.allowed_getattr, allowed_methods=self._getattr_methods, allowed_external=allowed_getattr_external, method_name="__getattr__", ) accept = False # Many objects do not have `__getattr__`, this is fine. if has_original_attr is None and has_original_attribute: accept = True else: # Accept objects without modifications to `__getattr__` and `__getattribute__` accept = has_original_attr and has_original_attribute if accept: # We still need to check for overridden properties. value_class = type(value) if not hasattr(value_class, attr): return True class_attr_val = getattr(value_class, attr) is_property = isinstance(class_attr_val, property) if not is_property: return True # Properties in allowed types are ok (although we do not include any # properties in our default allow list currently). if type(value) in self.allowed_getattr: return True # pragma: no cover # Properties in subclasses of allowed types may be ok if not changed for module_name, *access_path in allowed_getattr_external: try: external_class = _get_external(module_name, access_path) external_class_attr_val = getattr(external_class, attr) except (KeyError, AttributeError): return False # pragma: no cover return class_attr_val == external_class_attr_val return False def can_get_item(self, value, item): """Allow accessing `__getiitem__` of allow-listed instances unless it was not modified.""" allowed_getitem_external = _coerce_path_to_tuples(self.allowed_getitem_external) if self.allow_getitem_on_types: # e.g. Union[str, int] or Literal[True, 1] if isinstance(value, (typing._SpecialForm, typing._BaseGenericAlias)): return True # PEP 560 e.g. list[str] if isinstance(value, type) and hasattr(value, "__class_getitem__"): return True return _has_original_dunder( value, allowed_types=self.allowed_getitem, allowed_methods=self._getitem_methods, allowed_external=allowed_getitem_external, method_name="__getitem__", ) def can_operate(self, dunders: tuple[str, ...], a, b=None): allowed_operations_external = _coerce_path_to_tuples( self.allowed_operations_external ) objects = [a] if b is not None: objects.append(b) return all( [ _has_original_dunder( obj, allowed_types=self.allowed_operations, allowed_methods=self._operator_dunder_methods(dunder), allowed_external=allowed_operations_external, method_name=dunder, ) for dunder in dunders for obj in objects ] ) def _operator_dunder_methods(self, dunder: str) -> set[Callable]: if dunder not in self._operation_methods_cache: self._operation_methods_cache[dunder] = self._safe_get_methods( self.allowed_operations, dunder ) return self._operation_methods_cache[dunder] @cached_property def _getitem_methods(self) -> set[Callable]: return self._safe_get_methods(self.allowed_getitem, "__getitem__") @cached_property def _getattr_methods(self) -> set[Callable]: return self._safe_get_methods(self.allowed_getattr, "__getattr__") @cached_property def _getattribute_methods(self) -> set[Callable]: return self._safe_get_methods(self.allowed_getattr, "__getattribute__") def _safe_get_methods(self, classes, name) -> set[Callable]: return { method for class_ in classes for method in [getattr(class_, name, None)] if method } class _DummyNamedTuple(NamedTuple): """Used internally to retrieve methods of named tuple instance.""" EvaluationPolicyName = Literal["forbidden", "minimal", "limited", "unsafe", "dangerous"] @dataclass class EvaluationContext: #: Local namespace locals: dict #: Global namespace globals: dict #: Evaluation policy identifier evaluation: EvaluationPolicyName = "forbidden" #: Whether the evaluation of code takes place inside of a subscript. #: Useful for evaluating ``:-1, 'col'`` in ``df[:-1, 'col']``. in_subscript: bool = False #: Auto import method auto_import: Callable[[Sequence[str]], ModuleType] | None = None #: Overrides for evaluation policy policy_overrides: dict = field(default_factory=dict) #: Transient local namespace used to store mocks transient_locals: dict = field(default_factory=dict) #: Transients of class level class_transients: dict | None = None #: Instance variable name used in the method definition instance_arg_name: str | None = None #: Currently associated value #: Useful for adding items to _Duck on annotated assignment current_value: ast.AST | None = None def replace(self, /, **changes): """Return a new copy of the context, with specified changes""" return dataclasses.replace(self, **changes) class _IdentitySubscript: """Returns the key itself when item is requested via subscript.""" def __getitem__(self, key): return key IDENTITY_SUBSCRIPT = _IdentitySubscript() SUBSCRIPT_MARKER = "__SUBSCRIPT_SENTINEL__" UNKNOWN_SIGNATURE = Signature() NOT_EVALUATED = object() class GuardRejection(Exception): """Exception raised when guard rejects evaluation attempt.""" pass def guarded_eval(code: str, context: EvaluationContext): """Evaluate provided code in the evaluation context. If evaluation policy given by context is set to ``forbidden`` no evaluation will be performed; if it is set to ``dangerous`` standard :func:`eval` will be used; finally, for any other, policy :func:`eval_node` will be called on parsed AST. """ locals_ = context.locals if context.evaluation == "forbidden": raise GuardRejection("Forbidden mode") # note: not using `ast.literal_eval` as it does not implement # getitem at all, for example it fails on simple `[0][1]` if context.in_subscript: # syntactic sugar for ellipsis (:) is only available in subscripts # so we need to trick the ast parser into thinking that we have # a subscript, but we need to be able to later recognise that we did # it so we can ignore the actual __getitem__ operation if not code: return tuple() locals_ = locals_.copy() locals_[SUBSCRIPT_MARKER] = IDENTITY_SUBSCRIPT code = SUBSCRIPT_MARKER + "[" + code + "]" context = context.replace(locals=locals_) if context.evaluation == "dangerous": return eval(code, context.globals, context.locals) node = ast.parse(code, mode="exec") return eval_node(node, context) BINARY_OP_DUNDERS: dict[type[ast.operator], tuple[str]] = { ast.Add: ("__add__",), ast.Sub: ("__sub__",), ast.Mult: ("__mul__",), ast.Div: ("__truediv__",), ast.FloorDiv: ("__floordiv__",), ast.Mod: ("__mod__",), ast.Pow: ("__pow__",), ast.LShift: ("__lshift__",), ast.RShift: ("__rshift__",), ast.BitOr: ("__or__",), ast.BitXor: ("__xor__",), ast.BitAnd: ("__and__",), ast.MatMult: ("__matmul__",), } COMP_OP_DUNDERS: dict[type[ast.cmpop], tuple[str, ...]] = { ast.Eq: ("__eq__",), ast.NotEq: ("__ne__", "__eq__"), ast.Lt: ("__lt__", "__gt__"), ast.LtE: ("__le__", "__ge__"), ast.Gt: ("__gt__", "__lt__"), ast.GtE: ("__ge__", "__le__"), ast.In: ("__contains__",), # Note: ast.Is, ast.IsNot, ast.NotIn are handled specially } UNARY_OP_DUNDERS: dict[type[ast.unaryop], tuple[str, ...]] = { ast.USub: ("__neg__",), ast.UAdd: ("__pos__",), # we have to check both __inv__ and __invert__! ast.Invert: ("__invert__", "__inv__"), ast.Not: ("__not__",), } GENERIC_CONTAINER_TYPES = (dict, list, set, tuple, frozenset) class ImpersonatingDuck: """A dummy class used to create objects of other classes without calling their ``__init__``""" # no-op: override __class__ to impersonate class _Duck: """A dummy class used to create objects pretending to have given attributes""" def __init__(self, attributes: Optional[dict] = None, items: Optional[dict] = None): self.attributes = attributes if attributes is not None else {} self.items = items if items is not None else {} def __getattr__(self, attr: str): return self.attributes[attr] def __hasattr__(self, attr: str): return attr in self.attributes def __dir__(self): return [*dir(super), *self.attributes] def __getitem__(self, key: str): return self.items[key] def __hasitem__(self, key: str): return self.items[key] def _ipython_key_completions_(self): return self.items.keys() def _find_dunder(node_op, dunders) -> Union[tuple[str, ...], None]: dunder = None for op, candidate_dunder in dunders.items(): if isinstance(node_op, op): dunder = candidate_dunder return dunder def get_policy(context: EvaluationContext) -> EvaluationPolicy: policy = copy(EVALUATION_POLICIES[context.evaluation]) for key, value in context.policy_overrides.items(): if hasattr(policy, key): setattr(policy, key, value) return policy def _validate_policy_overrides( policy_name: EvaluationPolicyName, policy_overrides: dict ) -> bool: policy = EVALUATION_POLICIES[policy_name] all_good = True for key, value in policy_overrides.items(): if not hasattr(policy, key): warnings.warn( f"Override {key!r} is not valid with {policy_name!r} evaluation policy" ) all_good = False return all_good def _is_type_annotation(obj) -> bool: """ Returns True if obj is a type annotation, False otherwise. """ if isinstance(obj, type): return True if isinstance(obj, types.GenericAlias): return True if hasattr(types, "UnionType") and isinstance(obj, types.UnionType): return True if isinstance(obj, (typing._SpecialForm, typing._BaseGenericAlias)): return True if isinstance(obj, typing.TypeVar): return True # Types that support __class_getitem__ if isinstance(obj, type) and hasattr(obj, "__class_getitem__"): return True # Fallback: check if get_origin returns something if hasattr(typing, "get_origin") and get_origin(obj) is not None: return True return False def _handle_assign(node: ast.Assign, context: EvaluationContext): value = eval_node(node.value, context) transient_locals = context.transient_locals policy = get_policy(context) class_transients = context.class_transients for target in node.targets: if isinstance(target, (ast.Tuple, ast.List)): # Handle unpacking assignment values = list(value) targets = target.elts starred = [i for i, t in enumerate(targets) if isinstance(t, ast.Starred)] # Unified handling: treat no starred as starred at end star_or_last_idx = starred[0] if starred else len(targets) # Before starred for i in range(star_or_last_idx): # Check for self.x assignment if _is_instance_attribute_assignment(targets[i], context): class_transients[targets[i].attr] = values[i] else: transient_locals[targets[i].id] = values[i] # Starred if exists if starred: end = len(values) - (len(targets) - star_or_last_idx - 1) if _is_instance_attribute_assignment( targets[star_or_last_idx], context ): class_transients[targets[star_or_last_idx].attr] = values[ star_or_last_idx:end ] else: transient_locals[targets[star_or_last_idx].value.id] = values[ star_or_last_idx:end ] # After starred for i in range(star_or_last_idx + 1, len(targets)): if _is_instance_attribute_assignment(targets[i], context): class_transients[targets[i].attr] = values[ len(values) - (len(targets) - i) ] else: transient_locals[targets[i].id] = values[ len(values) - (len(targets) - i) ] elif isinstance(target, ast.Subscript): if isinstance(target.value, ast.Name): name = target.value.id container = transient_locals.get(name) if container is None: container = context.locals.get(name) if container is None: container = context.globals.get(name) if container is None: raise NameError( f"{name} not found in locals, globals, nor builtins" ) storage_dict = transient_locals storage_key = name elif isinstance( target.value, ast.Attribute ) and _is_instance_attribute_assignment(target.value, context): attr = target.value.attr container = class_transients.get(attr, None) if container is None: raise NameError(f"{attr} not found in class transients") storage_dict = class_transients storage_key = attr else: return key = eval_node(target.slice, context) attributes = ( dict.fromkeys(dir(container)) if policy.can_call(container.__dir__) else {} ) items = {} if policy.can_get_item(container, None): try: items = dict(container.items()) except Exception: pass items[key] = value duck_container = _Duck(attributes=attributes, items=items) storage_dict[storage_key] = duck_container elif _is_instance_attribute_assignment(target, context): class_transients[target.attr] = value else: transient_locals[target.id] = value return None def _handle_annassign(node, context): context_with_value = context.replace(current_value=getattr(node, "value", None)) annotation_result = eval_node(node.annotation, context_with_value) if _is_type_annotation(annotation_result): annotation_value = _resolve_annotation(annotation_result, context) # Use Value for generic types use_value = ( isinstance(annotation_value, GENERIC_CONTAINER_TYPES) and node.value is not None ) else: annotation_value = annotation_result use_value = False # LOCAL VARIABLE if getattr(node, "simple", False) and isinstance(node.target, ast.Name): name = node.target.id if use_value: return _handle_assign( ast.Assign(targets=[node.target], value=node.value), context ) context.transient_locals[name] = annotation_value return None # INSTANCE ATTRIBUTE if _is_instance_attribute_assignment(node.target, context): attr = node.target.attr if use_value: return _handle_assign( ast.Assign(targets=[node.target], value=node.value), context ) context.class_transients[attr] = annotation_value return None return None def _extract_args_and_kwargs(node: ast.Call, context: EvaluationContext): args = [eval_node(arg, context) for arg in node.args] kwargs = { k: v for kw in node.keywords for k, v in ( {kw.arg: eval_node(kw.value, context)} if kw.arg else eval_node(kw.value, context) ).items() } return args, kwargs def _is_instance_attribute_assignment( target: ast.AST, context: EvaluationContext ) -> bool: """Return True if target is an attribute access on the instance argument.""" return ( context.class_transients is not None and context.instance_arg_name is not None and isinstance(target, ast.Attribute) and isinstance(getattr(target, "value", None), ast.Name) and getattr(target.value, "id", None) == context.instance_arg_name ) def _get_coroutine_attributes() -> dict[str, Optional[object]]: async def _dummy(): return None coro = _dummy() try: return {attr: getattr(coro, attr, None) for attr in dir(coro)} finally: coro.close() def eval_node(node: Union[ast.AST, None], context: EvaluationContext): """Evaluate AST node in provided context. Applies evaluation restrictions defined in the context. Currently does not support evaluation of functions with keyword arguments. Does not evaluate actions that always have side effects: - class definitions (``class sth: ...``) - function definitions (``def sth: ...``) - variable assignments (``x = 1``) - augmented assignments (``x += 1``) - deletions (``del x``) Does not evaluate operations which do not return values: - assertions (``assert x``) - pass (``pass``) - imports (``import x``) - control flow: - conditionals (``if x:``) except for ternary IfExp (``a if x else b``) - loops (``for`` and ``while``) - exception handling The purpose of this function is to guard against unwanted side-effects; it does not give guarantees on protection from malicious code execution. """ policy = get_policy(context) if node is None: return None if isinstance(node, (ast.Interactive, ast.Module)): result = None for child_node in node.body: result = eval_node(child_node, context) return result if isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef)): is_async = isinstance(node, ast.AsyncFunctionDef) func_locals = context.transient_locals.copy() func_context = context.replace(transient_locals=func_locals) is_property = False is_static = False is_classmethod = False for decorator_node in node.decorator_list: try: decorator = eval_node(decorator_node, context) except NameError: # if the decorator is not yet defined this is fine # especialy because we don't handle imports yet continue if decorator is property: is_property = True elif decorator is staticmethod: is_static = True elif decorator is classmethod: is_classmethod = True if func_context.class_transients is not None: if not is_static and not is_classmethod: func_context.instance_arg_name = ( node.args.args[0].arg if node.args.args else None ) return_type = eval_node(node.returns, context=context) for child_node in node.body: eval_node(child_node, func_context) if is_property: if return_type is not None: if _is_type_annotation(return_type): context.transient_locals[node.name] = _resolve_annotation( return_type, context ) else: context.transient_locals[node.name] = return_type else: return_value = _infer_return_value(node, func_context) context.transient_locals[node.name] = return_value return None def dummy_function(*args, **kwargs): pass if return_type is not None: if _is_type_annotation(return_type): dummy_function.__annotations__["return"] = return_type else: dummy_function.__inferred_return__ = return_type else: inferred_return = _infer_return_value(node, func_context) if inferred_return is not None: dummy_function.__inferred_return__ = inferred_return dummy_function.__name__ = node.name dummy_function.__node__ = node dummy_function.__is_async__ = is_async context.transient_locals[node.name] = dummy_function return None if isinstance(node, ast.Lambda): def dummy_function(*args, **kwargs): pass dummy_function.__inferred_return__ = eval_node(node.body, context) return dummy_function if isinstance(node, ast.ClassDef): # TODO support class decorators? class_locals = {} outer_locals = context.locals.copy() outer_locals.update(context.transient_locals) class_context = context.replace( transient_locals=class_locals, locals=outer_locals ) class_context.class_transients = class_locals for child_node in node.body: eval_node(child_node, class_context) bases = tuple([eval_node(base, context) for base in node.bases]) dummy_class = type(node.name, bases, class_locals) context.transient_locals[node.name] = dummy_class return None if isinstance(node, ast.Await): value = eval_node(node.value, context) if hasattr(value, "__awaited_type__"): return value.__awaited_type__ return value if isinstance(node, ast.While): loop_locals = context.transient_locals.copy() loop_context = context.replace(transient_locals=loop_locals) result = None for stmt in node.body: result = eval_node(stmt, loop_context) policy = get_policy(context) merged_locals = _merge_dicts_by_key( [loop_locals, context.transient_locals.copy()], policy ) context.transient_locals.update(merged_locals) return result if isinstance(node, ast.For): try: iterable = eval_node(node.iter, context) except Exception: iterable = None sample = None if iterable is not None: try: if policy.can_call(getattr(iterable, "__iter__", None)): sample = next(iter(iterable)) except Exception: sample = None loop_locals = context.transient_locals.copy() loop_context = context.replace(transient_locals=loop_locals) if sample is not None: try: fake_assign = ast.Assign( targets=[node.target], value=ast.Constant(value=sample) ) _handle_assign(fake_assign, loop_context) except Exception: pass result = None for stmt in node.body: result = eval_node(stmt, loop_context) policy = get_policy(context) merged_locals = _merge_dicts_by_key( [loop_locals, context.transient_locals.copy()], policy ) context.transient_locals.update(merged_locals) return result if isinstance(node, ast.If): branches = [] current = node result = None while True: branch_locals = context.transient_locals.copy() branch_context = context.replace(transient_locals=branch_locals) for stmt in current.body: result = eval_node(stmt, branch_context) branches.append(branch_locals) if not current.orelse: break elif len(current.orelse) == 1 and isinstance(current.orelse[0], ast.If): # It's an elif - continue loop current = current.orelse[0] else: # It's an else block - process and break else_locals = context.transient_locals.copy() else_context = context.replace(transient_locals=else_locals) for stmt in current.orelse: result = eval_node(stmt, else_context) branches.append(else_locals) break branches.append(context.transient_locals.copy()) policy = get_policy(context) merged_locals = _merge_dicts_by_key(branches, policy) context.transient_locals.update(merged_locals) return result if isinstance(node, ast.Assign): return _handle_assign(node, context) if isinstance(node, ast.AnnAssign): return _handle_annassign(node, context) if isinstance(node, ast.Expression): return eval_node(node.body, context) if isinstance(node, ast.Expr): return eval_node(node.value, context) if isinstance(node, ast.Pass): return None if isinstance(node, ast.Import): # TODO: populate transient_locals return None if isinstance(node, (ast.AugAssign, ast.Delete)): return None if isinstance(node, (ast.Global, ast.Nonlocal)): return None if isinstance(node, ast.BinOp): left = eval_node(node.left, context) right = eval_node(node.right, context) if ( isinstance(node.op, ast.BitOr) and _is_type_annotation(left) and _is_type_annotation(right) ): left_duck = ( _Duck(dict.fromkeys(dir(left))) if policy.can_call(left.__dir__) else _Duck() ) right_duck = ( _Duck(dict.fromkeys(dir(right))) if policy.can_call(right.__dir__) else _Duck() ) value_node = context.current_value if value_node is not None and isinstance(value_node, ast.Dict): if dict in [left, right]: return _merge_values( [left_duck, right_duck, ast.literal_eval(value_node)], policy=get_policy(context), ) return _merge_values([left_duck, right_duck], policy=get_policy(context)) dunders = _find_dunder(node.op, BINARY_OP_DUNDERS) if dunders: if policy.can_operate(dunders, left, right): return getattr(left, dunders[0])(right) else: raise GuardRejection( f"Operation (`{dunders}`) for", type(left), f"not allowed in {context.evaluation} mode", ) if isinstance(node, ast.Compare): left = eval_node(node.left, context) all_true = True negate = False for op, right in zip(node.ops, node.comparators): right = eval_node(right, context) dunder = None dunders = _find_dunder(op, COMP_OP_DUNDERS) if not dunders: if isinstance(op, ast.NotIn): dunders = COMP_OP_DUNDERS[ast.In] negate = True if isinstance(op, ast.Is): dunder = "is_" if isinstance(op, ast.IsNot): dunder = "is_" negate = True if not dunder and dunders: dunder = dunders[0] if dunder: a, b = (right, left) if dunder == "__contains__" else (left, right) if dunder == "is_" or dunders and policy.can_operate(dunders, a, b): result = getattr(operator, dunder)(a, b) if negate: result = not result if not result: all_true = False left = right else: raise GuardRejection( f"Comparison (`{dunder}`) for", type(left), f"not allowed in {context.evaluation} mode", ) else: raise ValueError( f"Comparison `{dunder}` not supported" ) # pragma: no cover return all_true if isinstance(node, ast.Constant): return node.value if isinstance(node, ast.Tuple): return tuple(eval_node(e, context) for e in node.elts) if isinstance(node, ast.List): return [eval_node(e, context) for e in node.elts] if isinstance(node, ast.Set): return {eval_node(e, context) for e in node.elts} if isinstance(node, ast.Dict): return dict( zip( [eval_node(k, context) for k in node.keys], [eval_node(v, context) for v in node.values], ) ) if isinstance(node, ast.Slice): return slice( eval_node(node.lower, context), eval_node(node.upper, context), eval_node(node.step, context), ) if isinstance(node, ast.UnaryOp): value = eval_node(node.operand, context) dunders = _find_dunder(node.op, UNARY_OP_DUNDERS) if dunders: if policy.can_operate(dunders, value): try: return getattr(value, dunders[0])() except AttributeError: raise TypeError( f"bad operand type for unary {node.op}: {type(value)}" ) else: raise GuardRejection( f"Operation (`{dunders}`) for", type(value), f"not allowed in {context.evaluation} mode", ) if isinstance(node, ast.Subscript): value = eval_node(node.value, context) slice_ = eval_node(node.slice, context) if policy.can_get_item(value, slice_): return value[slice_] raise GuardRejection( "Subscript access (`__getitem__`) for", type(value), # not joined to avoid calling `repr` f" not allowed in {context.evaluation} mode", ) if isinstance(node, ast.Name): return _eval_node_name(node.id, context) if isinstance(node, ast.Attribute): if ( context.class_transients is not None and isinstance(node.value, ast.Name) and node.value.id == context.instance_arg_name ): return context.class_transients.get(node.attr) value = eval_node(node.value, context) if policy.can_get_attr(value, node.attr): return getattr(value, node.attr) try: cls = ( value if isinstance(value, type) else getattr(value, "__class__", None) ) if cls is not None: resolved_hints = get_type_hints( cls, globalns=(context.globals or {}), localns=(context.locals or {}), ) if node.attr in resolved_hints: annotated = resolved_hints[node.attr] return _resolve_annotation(annotated, context) except Exception: # Fall through to the guard rejection pass raise GuardRejection( "Attribute access (`__getattr__`) for", type(value), # not joined to avoid calling `repr` f"not allowed in {context.evaluation} mode", ) if isinstance(node, ast.IfExp): test = eval_node(node.test, context) if test: return eval_node(node.body, context) else: return eval_node(node.orelse, context) if isinstance(node, ast.Call): func = eval_node(node.func, context) if policy.can_call(func): args, kwargs = _extract_args_and_kwargs(node, context) return func(*args, **kwargs) if isclass(func): # this code path gets entered when calling class e.g. `MyClass()` # or `my_instance.__class__()` - in both cases `func` is `MyClass`. # Should return `MyClass` if `__new__` is not overridden, # otherwise whatever `__new__` return type is. overridden_return_type = _eval_return_type(func.__new__, node, context) if overridden_return_type is not NOT_EVALUATED: return overridden_return_type return _create_duck_for_heap_type(func) else: inferred_return = getattr(func, "__inferred_return__", NOT_EVALUATED) return_type = _eval_return_type(func, node, context) if getattr(func, "__is_async__", False): awaited_type = ( inferred_return if inferred_return is not None else return_type ) coroutine_duck = _Duck(attributes=_get_coroutine_attributes()) coroutine_duck.__awaited_type__ = awaited_type return coroutine_duck if inferred_return is not NOT_EVALUATED: return inferred_return if return_type is not NOT_EVALUATED: return return_type raise GuardRejection( "Call for", func, # not joined to avoid calling `repr` f"not allowed in {context.evaluation} mode", ) if isinstance(node, ast.Assert): # message is always the second item, so if it is defined user would be completing # on the message, not on the assertion test if node.msg: return eval_node(node.msg, context) return eval_node(node.test, context) return None def _merge_dicts_by_key(dicts: list, policy: EvaluationPolicy): """Merge multiple dictionaries, combining values for each key.""" if len(dicts) == 1: return dicts[0] all_keys = set() for d in dicts: all_keys.update(d.keys()) merged = {} for key in all_keys: values = [d[key] for d in dicts if key in d] if values: merged[key] = _merge_values(values, policy) return merged def _merge_values(values, policy: EvaluationPolicy): """Recursively merge multiple values, combining attributes and dict items.""" if len(values) == 1: return values[0] types = {type(v) for v in values} merged_items = None key_values = {} attributes = set() for v in values: if policy.can_call(v.__dir__): attributes.update(dir(v)) try: if policy.can_call(v.items): try: for k, val in v.items(): key_values.setdefault(k, []).append(val) except Exception as e: pass elif policy.can_call(v.keys): try: for k in v.keys(): key_values.setdefault(k, []).append(None) except Exception as e: pass except Exception as e: pass if key_values: merged_items = { k: _merge_values(vals, policy) if vals[0] is not None else None for k, vals in key_values.items() } if len(types) == 1: t = next(iter(types)) if t not in (dict,) and not ( hasattr(next(iter(values)), "__getitem__") and ( hasattr(next(iter(values)), "items") or hasattr(next(iter(values)), "keys") ) ): if t in (list, set, tuple): return t return values[0] return _Duck(attributes=dict.fromkeys(attributes), items=merged_items) def _infer_return_value(node: ast.FunctionDef, context: EvaluationContext): """Infer the return value(s) of a function by evaluating all return statements.""" return_values = _collect_return_values(node.body, context) if not return_values: return None if len(return_values) == 1: return return_values[0] policy = get_policy(context) return _merge_values(return_values, policy) def _collect_return_values(body, context): """Recursively collect return values from a list of AST statements.""" return_values = [] for stmt in body: if isinstance(stmt, ast.Return): if stmt.value is None: continue try: value = eval_node(stmt.value, context) if value is not None and value is not NOT_EVALUATED: return_values.append(value) except Exception: pass if isinstance( stmt, (ast.FunctionDef, ast.AsyncFunctionDef, ast.ClassDef, ast.Lambda) ): continue elif hasattr(stmt, "body") and isinstance(stmt.body, list): return_values.extend(_collect_return_values(stmt.body, context)) if isinstance(stmt, ast.Try): for h in stmt.handlers: if hasattr(h, "body"): return_values.extend(_collect_return_values(h.body, context)) if hasattr(stmt, "orelse"): return_values.extend(_collect_return_values(stmt.orelse, context)) if hasattr(stmt, "finalbody"): return_values.extend(_collect_return_values(stmt.finalbody, context)) if hasattr(stmt, "orelse") and isinstance(stmt.orelse, list): return_values.extend(_collect_return_values(stmt.orelse, context)) return return_values def _eval_return_type(func: Callable, node: ast.Call, context: EvaluationContext): """Evaluate return type of a given callable function. Returns the built-in type, a duck or NOT_EVALUATED sentinel. """ try: sig = signature(func) except ValueError: sig = UNKNOWN_SIGNATURE # if annotation was not stringized, or it was stringized # but resolved by signature call we know the return type not_empty = sig.return_annotation is not Signature.empty if not_empty: return _resolve_annotation(sig.return_annotation, context, sig, func, node) return NOT_EVALUATED def _eval_annotation( annotation: str, context: EvaluationContext, ): return ( _eval_node_name(annotation, context) if isinstance(annotation, str) else annotation ) class _GetItemDuck(dict): """A dict subclass that always returns the factory instance and claims to have any item.""" def __init__(self, factory, *args, **kwargs): super().__init__(*args, **kwargs) self._factory = factory def __getitem__(self, key): return self._factory() def __contains__(self, key): return True def _resolve_annotation( annotation: object | str, context: EvaluationContext, sig: Signature | None = None, func: Callable | None = None, node: ast.Call | None = None, ): """Resolve annotation created by user with `typing` module and custom objects.""" if annotation is None: return None annotation = _eval_annotation(annotation, context) origin = get_origin(annotation) if annotation is Self and func and hasattr(func, "__self__"): return func.__self__ elif origin is Literal: type_args = get_args(annotation) if len(type_args) == 1: return type_args[0] elif annotation is LiteralString: return "" elif annotation is AnyStr: index = None if func and hasattr(func, "__node__"): def_node = func.__node__ for i, arg in enumerate(def_node.args.args): if not arg.annotation: continue annotation = _eval_annotation(arg.annotation.id, context) if annotation is AnyStr: index = i break is_bound_method = ( isinstance(func, MethodType) and getattr(func, "__self__") is not None ) if index and is_bound_method: index -= 1 elif sig: for i, (key, value) in enumerate(sig.parameters.items()): if value.annotation is AnyStr: index = i break if index is None: return None if index < 0 or index >= len(node.args): return None return eval_node(node.args[index], context) elif origin is TypeGuard: return False elif origin is set or origin is list: # only one type argument allowed attributes = [ attr for attr in dir( _resolve_annotation(get_args(annotation)[0], context, sig, func, node) ) ] duck = _Duck(attributes=dict.fromkeys(attributes)) return _Duck( attributes=dict.fromkeys(dir(origin())), # items are not strrictly needed for set items=_GetItemDuck(lambda: duck), ) elif origin is tuple: # multiple type arguments return tuple( _resolve_annotation(arg, context, sig, func, node) for arg in get_args(annotation) ) elif origin is Union: # multiple type arguments attributes = [ attr for type_arg in get_args(annotation) for attr in dir(_resolve_annotation(type_arg, context, sig, func, node)) ] return _Duck(attributes=dict.fromkeys(attributes)) elif is_typeddict(annotation): return _Duck( attributes=dict.fromkeys(dir(dict())), items={ k: _resolve_annotation(v, context, sig, func, node) for k, v in annotation.__annotations__.items() }, ) elif hasattr(annotation, "_is_protocol"): return _Duck(attributes=dict.fromkeys(dir(annotation))) elif origin is Annotated: type_arg = get_args(annotation)[0] return _resolve_annotation(type_arg, context, sig, func, node) elif isinstance(annotation, NewType): return _eval_or_create_duck(annotation.__supertype__, context) elif isinstance(annotation, TypeAliasType): return _eval_or_create_duck(annotation.__value__, context) else: return _eval_or_create_duck(annotation, context) def _eval_node_name(node_id: str, context: EvaluationContext): policy = get_policy(context) if node_id in context.transient_locals: return context.transient_locals[node_id] if policy.allow_locals_access and node_id in context.locals: return context.locals[node_id] if policy.allow_globals_access and node_id in context.globals: return context.globals[node_id] if policy.allow_builtins_access and hasattr(builtins, node_id): # note: do not use __builtins__, it is implementation detail of cPython return getattr(builtins, node_id) if policy.allow_auto_import and context.auto_import: return context.auto_import(node_id) if not policy.allow_globals_access and not policy.allow_locals_access: raise GuardRejection( f"Namespace access not allowed in {context.evaluation} mode" ) else: raise NameError(f"{node_id} not found in locals, globals, nor builtins") def _eval_or_create_duck(duck_type, context: EvaluationContext): policy = get_policy(context) # if allow-listed builtin is on type annotation, instantiate it if policy.can_call(duck_type): return duck_type() # if custom class is in type annotation, mock it return _create_duck_for_heap_type(duck_type) def _create_duck_for_heap_type(duck_type): """Create an imitation of an object of a given type (a duck). Returns the duck or NOT_EVALUATED sentinel if duck could not be created. """ duck = ImpersonatingDuck() try: # this only works for heap types, not builtins duck.__class__ = duck_type return duck except TypeError: pass return NOT_EVALUATED SUPPORTED_EXTERNAL_GETITEM = { ("pandas", "core", "indexing", "_iLocIndexer"), ("pandas", "core", "indexing", "_LocIndexer"), ("pandas", "DataFrame"), ("pandas", "Series"), ("numpy", "ndarray"), ("numpy", "void"), } BUILTIN_GETITEM: set[InstancesHaveGetItem] = { dict, str, # type: ignore[arg-type] bytes, # type: ignore[arg-type] list, tuple, type, # for type annotations like list[str] _Duck, collections.defaultdict, collections.deque, collections.OrderedDict, collections.ChainMap, collections.UserDict, collections.UserList, collections.UserString, # type: ignore[arg-type] _DummyNamedTuple, _IdentitySubscript, } def _list_methods(cls, source=None): """For use on immutable objects or with methods returning a copy""" return [getattr(cls, k) for k in (source if source else dir(cls))] dict_non_mutating_methods = ("copy", "keys", "values", "items") list_non_mutating_methods = ("copy", "index", "count") set_non_mutating_methods = set(dir(set)) & set(dir(frozenset)) dict_keys: type[collections.abc.KeysView] = type({}.keys()) dict_values: type = type({}.values()) dict_items: type = type({}.items()) NUMERICS = {int, float, complex} ALLOWED_CALLS = { bytes, *_list_methods(bytes), bytes.__iter__, dict, *_list_methods(dict, dict_non_mutating_methods), dict.__iter__, dict_keys.__iter__, dict_values.__iter__, dict_items.__iter__, dict_keys.isdisjoint, list, *_list_methods(list, list_non_mutating_methods), list.__iter__, set, *_list_methods(set, set_non_mutating_methods), set.__iter__, frozenset, *_list_methods(frozenset), frozenset.__iter__, range, range.__iter__, str, *_list_methods(str), str.__iter__, tuple, *_list_methods(tuple), tuple.__iter__, bool, *_list_methods(bool), *NUMERICS, *[method for numeric_cls in NUMERICS for method in _list_methods(numeric_cls)], collections.deque, *_list_methods(collections.deque, list_non_mutating_methods), collections.deque.__iter__, collections.defaultdict, *_list_methods(collections.defaultdict, dict_non_mutating_methods), collections.defaultdict.__iter__, collections.OrderedDict, *_list_methods(collections.OrderedDict, dict_non_mutating_methods), collections.OrderedDict.__iter__, collections.UserDict, *_list_methods(collections.UserDict, dict_non_mutating_methods), collections.UserDict.__iter__, collections.UserList, *_list_methods(collections.UserList, list_non_mutating_methods), collections.UserList.__iter__, collections.UserString, *_list_methods(collections.UserString, dir(str)), collections.UserString.__iter__, collections.Counter, *_list_methods(collections.Counter, dict_non_mutating_methods), collections.Counter.__iter__, collections.Counter.elements, collections.Counter.most_common, object.__dir__, type.__dir__, _Duck.__dir__, } BUILTIN_GETATTR: set[MayHaveGetattr] = { *BUILTIN_GETITEM, set, frozenset, object, type, # `type` handles a lot of generic cases, e.g. numbers as in `int.real`. *NUMERICS, dict_keys, MethodDescriptorType, ModuleType, } BUILTIN_OPERATIONS = {*BUILTIN_GETATTR} EVALUATION_POLICIES = { "minimal": EvaluationPolicy( allow_builtins_access=True, allow_locals_access=False, allow_globals_access=False, allow_item_access=False, allow_attr_access=False, allowed_calls=set(), allow_any_calls=False, allow_all_operations=False, ), "limited": SelectivePolicy( allowed_getitem=BUILTIN_GETITEM, allowed_getitem_external=SUPPORTED_EXTERNAL_GETITEM, allowed_getattr=BUILTIN_GETATTR, allowed_getattr_external={ # pandas Series/Frame implements custom `__getattr__` ("pandas", "DataFrame"), ("pandas", "Series"), }, allowed_operations=BUILTIN_OPERATIONS, allow_builtins_access=True, allow_locals_access=True, allow_globals_access=True, allow_getitem_on_types=True, allowed_calls=ALLOWED_CALLS, ), "unsafe": EvaluationPolicy( allow_builtins_access=True, allow_locals_access=True, allow_globals_access=True, allow_attr_access=True, allow_item_access=True, allow_any_calls=True, allow_all_operations=True, ), } __all__ = [ "guarded_eval", "eval_node", "GuardRejection", "EvaluationContext", "_unbind_method", ]