[Python-checkins] bpo-41341: Recursive evaluation of ForwardRef in get_type_hints (#21553)
wyfo
webhook-mailer at python.org
Wed Jul 22 15:47:37 EDT 2020
https://github.com/python/cpython/commit/653f420b53a3aa87316cef59de8d3f5d9e11deb4
commit: 653f420b53a3aa87316cef59de8d3f5d9e11deb4
branch: master
author: wyfo <joperez at hotmail.fr>
committer: GitHub <noreply at github.com>
date: 2020-07-22T12:47:28-07:00
summary:
bpo-41341: Recursive evaluation of ForwardRef in get_type_hints (#21553)
The issue raised by recursive evaluation is infinite recursion with
recursive types. In that case, only the first recursive ForwardRef is
evaluated.
files:
A Misc/NEWS.d/next/Library/2020-07-20-19-13-17.bpo-41341.wqrj8C.rst
M Lib/test/test_typing.py
M Lib/typing.py
diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
index 398add05a12b9..7f96aff710455 100644
--- a/Lib/test/test_typing.py
+++ b/Lib/test/test_typing.py
@@ -2456,6 +2456,12 @@ def foo(a: tuple[ForwardRef('T')]):
self.assertEqual(get_type_hints(foo, globals(), locals()),
{'a': tuple[T]})
+ def test_double_forward(self):
+ def foo(a: 'List[\'int\']'):
+ pass
+ self.assertEqual(get_type_hints(foo, globals(), locals()),
+ {'a': List[int]})
+
def test_forward_recursion_actually(self):
def namespace1():
a = typing.ForwardRef('A')
diff --git a/Lib/typing.py b/Lib/typing.py
index fd657caafee87..5da032bbee8f1 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -244,14 +244,16 @@ def inner(*args, **kwds):
return inner
-def _eval_type(t, globalns, localns):
+def _eval_type(t, globalns, localns, recursive_guard=frozenset()):
"""Evaluate all forward reverences in the given type t.
For use of globalns and localns see the docstring for get_type_hints().
+ recursive_guard is used to prevent prevent infinite recursion
+ with recursive ForwardRef.
"""
if isinstance(t, ForwardRef):
- return t._evaluate(globalns, localns)
+ return t._evaluate(globalns, localns, recursive_guard)
if isinstance(t, (_GenericAlias, GenericAlias)):
- ev_args = tuple(_eval_type(a, globalns, localns) for a in t.__args__)
+ ev_args = tuple(_eval_type(a, globalns, localns, recursive_guard) for a in t.__args__)
if ev_args == t.__args__:
return t
if isinstance(t, GenericAlias):
@@ -477,7 +479,9 @@ def __init__(self, arg, is_argument=True):
self.__forward_value__ = None
self.__forward_is_argument__ = is_argument
- def _evaluate(self, globalns, localns):
+ def _evaluate(self, globalns, localns, recursive_guard):
+ if self.__forward_arg__ in recursive_guard:
+ return self
if not self.__forward_evaluated__ or localns is not globalns:
if globalns is None and localns is None:
globalns = localns = {}
@@ -485,10 +489,14 @@ def _evaluate(self, globalns, localns):
globalns = localns
elif localns is None:
localns = globalns
- self.__forward_value__ = _type_check(
+ type_ =_type_check(
eval(self.__forward_code__, globalns, localns),
"Forward references must evaluate to types.",
- is_argument=self.__forward_is_argument__)
+ is_argument=self.__forward_is_argument__,
+ )
+ self.__forward_value__ = _eval_type(
+ type_, globalns, localns, recursive_guard | {self.__forward_arg__}
+ )
self.__forward_evaluated__ = True
return self.__forward_value__
diff --git a/Misc/NEWS.d/next/Library/2020-07-20-19-13-17.bpo-41341.wqrj8C.rst b/Misc/NEWS.d/next/Library/2020-07-20-19-13-17.bpo-41341.wqrj8C.rst
new file mode 100644
index 0000000000000..c78b24d2faae7
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-07-20-19-13-17.bpo-41341.wqrj8C.rst
@@ -0,0 +1 @@
+Recursive evaluation of `typing.ForwardRef` in `get_type_hints`.
\ No newline at end of file
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