# -*- coding: utf-8 -*-
"""
Python language utilities and tools.
"""
import functools
import inspect
from typing import Any, Callable
[docs]def protected(check: bool = False) -> Callable[[Callable[..., Any]], Callable[..., Any]]:
def wrap(func: Callable[..., Any]) -> Callable[..., Any]:
if isinstance(func, property):
raise RuntimeError('Protected must go after @property decorator')
args = inspect.getfullargspec(func)[0]
if len(args) == 0:
raise RuntimeError('Can only use the protected decorator on member functions')
# We can only perform checks if the interpreter is capable of giving
# us the stack i.e. currentframe() produces a valid object
if check and inspect.currentframe() is not None:
@functools.wraps(func)
def wrapped_fn(self: Any, *args: Any, **kwargs: Any) -> Callable[..., Any]:
try:
calling_class = inspect.stack()[1][0].f_locals['self']
assert self is calling_class
except (KeyError, AssertionError):
raise RuntimeError(f'Cannot access protected function {func.__name__} from outside class hierarchy')
return func(self, *args, **kwargs)
else:
wrapped_fn = func
return wrapped_fn
return wrap
[docs]def override(check: bool = False) -> Callable[[Callable[..., Any]], Callable[..., Any]]:
"""Decorator to override a superclass method."""
def wrap(func: Callable[..., Any]) -> Callable[..., Any]:
if isinstance(func, property):
raise RuntimeError('Override must go after @property decorator')
args = inspect.getfullargspec(func)[0]
if len(args) == 0:
raise RuntimeError('Can only use the override decorator on member functions')
if check:
@functools.wraps(func)
def wrapped_fn(self: Any, *args: Any, **kwargs: Any) -> Callable[..., Any]:
try:
getattr(super(self.__class__, self), func.__name__)
except AttributeError:
raise RuntimeError(f'Function {func} does not override a superclass method')
return func(self, *args, **kwargs)
else:
wrapped_fn = func
return wrapped_fn
return wrap
[docs]class __NULL: # pylint: disable=invalid-name
def __eq__(self, other: Any) -> bool:
return isinstance(other, self.__class__)
NULL = __NULL()
