bpo-37806:Add check recursion in typeing.ForwardRef when get hash. #15559
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| Fix infinite recursion from :func:`typing.get_type_hints`.Patch by hongweipeng. | |||
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| Fix infinite recursion from :func:`typing.get_type_hints`.Patch by hongweipeng. | |
| Fix infinite recursion from :func:`typing.get_type_hints`. Patch by hongweipeng. |
Lib/typing.py
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| if isinstance(val, _GenericAlias): | ||
| self._check_recursion(val, forward_args) | ||
| elif self is val and self.__forward_evaluated__: | ||
| forward_args.append(...) |
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Is it possible to create an actually recursive object? Or is it too dangerous?
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What does an actually recursive object mean? I added some test code in new commit. Can you have a look and see what other tests need to be added. Thanks.
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a = List['int']
for i in range(sys.getrecursionlimit() + 100):
a = List[a]
It raises a RecursionError both in this PR and master branch. Is an actually recursive object mean this?
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No. Consider the initial example:
ValueList = List['Value']
Value = Union[str, ValueList]In this example I mean trying to construct an object Value such that Value.__args__[1].__args__[0] is Value. I understand this may be tricky, but I don't think it is impossible.
Also it indeed looks like this may be "dangerous" in the sense that we need to make __repr__(), __eq__(), and __hash__() aware of the possible recursion.
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On the other hand:
>>> x = [1]
>>> x.append(x)
>>> x
[1, [...]]
>>> y = [1]
>>> y.append(y)
>>> x == y
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
RecursionError: maximum recursion depth exceeded in comparison
So maybe it would be enough to just update the __repr__().
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/cc @ilevkivskyi |
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PR #15650 can solve this issue. |
https://bugs.python.org/issue37806