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bpo-37806:Add check recursion in typeing.ForwardRef when get hash. #15559

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fb1944f
Fix infinite recursion with typing.get_type_hints.
hongweipeng Aug 28, 2019
85a9692
code review and add test
hongweipeng Aug 28, 2019
97728f0
keep the __forward_value__ type by using copy_with
hongweipeng Aug 29, 2019
be79f5a
add __filter_recursion_value__ to save _check_recursion return
hongweipeng Aug 31, 2019
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32 changes: 32 additions & 0 deletions Lib/test/test_typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2364,6 +2364,38 @@ def foo(a: Union['T']):
self.assertEqual(get_type_hints(foo, globals(), locals()),
{'a': Union[T]})

def test_union_forward_recursion(self):
ValueList = List['Value']
Value = Union[str, ValueList]

class C:
foo: List[Value]
class D:
foo: Union[Value, ValueList]
class E:
foo: Union[List[Value], ValueList]
class F:
foo: Union[Value, List[Value], ValueList]

self.assertEqual(get_type_hints(C, globals(), locals()), get_type_hints(C, globals(), locals()))
self.assertEqual(get_type_hints(C, globals(), locals()),
{'foo': List[Union[str, List[Union[str, List['Value']]]]]})
self.assertEqual(get_type_hints(D, globals(), locals()),
{'foo': Union[str, List[Union[str, List['Value']]]]})
self.assertEqual(get_type_hints(E, globals(), locals()),
{'foo': Union[
List[Union[str, List[Union[str, List['Value']]]]],
List[Union[str, List['Value']]]
]
})
self.assertEqual(get_type_hints(F, globals(), locals()),
{'foo': Union[
str,
List[Union[str, List['Value']]],
List[Union[str, List[Union[str, List['Value']]]]]
]
})

def test_tuple_forward(self):

def foo(a: Tuple['T']):
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19 changes: 17 additions & 2 deletions Lib/typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -491,7 +491,7 @@ class ForwardRef(_Final, _root=True):

__slots__ = ('__forward_arg__', '__forward_code__',
'__forward_evaluated__', '__forward_value__',
'__forward_is_argument__')
'__forward_is_argument__', '__filter_recursion_value__')

def __init__(self, arg, is_argument=True):
if not isinstance(arg, str):
Expand All @@ -505,6 +505,7 @@ def __init__(self, arg, is_argument=True):
self.__forward_evaluated__ = False
self.__forward_value__ = None
self.__forward_is_argument__ = is_argument
self.__filter_recursion_value__ = None

def _evaluate(self, globalns, localns):
if not self.__forward_evaluated__ or localns is not globalns:
Expand All @@ -521,14 +522,28 @@ def _evaluate(self, globalns, localns):
self.__forward_evaluated__ = True
return self.__forward_value__

def _check_recursion(self, value, forward_args):
for val in value.__args__:
if isinstance(val, _GenericAlias):
self._check_recursion(val, forward_args)
elif self is val:
forward_args.append(...)
else:
forward_args.append(val)
return tuple(forward_args)

def __eq__(self, other):
if not isinstance(other, ForwardRef):
return NotImplemented
return (self.__forward_arg__ == other.__forward_arg__ and
self.__forward_value__ == other.__forward_value__)

def __hash__(self):
return hash((self.__forward_arg__, self.__forward_value__))
forward_value = self.__forward_value__
if self.__forward_evaluated__ and not self.__filter_recursion_value__ \
and isinstance(forward_value, _GenericAlias):
self.__filter_recursion_value__ = forward_value.copy_with(self._check_recursion(forward_value, []))
return hash((self.__forward_arg__, self.__filter_recursion_value__ or forward_value))

def __repr__(self):
return f'ForwardRef({self.__forward_arg__!r})'
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2019-08-28-19-00-50.bpo-37806.HdrlIB.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Fix infinite recursion from :func:`typing.get_type_hints`. Patch by hongweipeng.