8000 bpo-41370: Evaluate strings as forward refs in PEP 585 generics (GH-3… · python/cpython@b465b60 · GitHub
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NiklasRosensteinJelleZijlstraAlexWaygood
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bpo-41370: Evaluate strings as forward refs in PEP 585 generics (GH-30900)
This removes discrepancy between list["int"] and List["int"]. Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com> Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
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‎Lib/test/test_typing.py

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Original file line numberDiff line numberDiff line change
@@ -32,6 +32,7 @@
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from typing import ParamSpec, Concatenate, ParamSpecArgs, ParamSpecKwargs
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from typing import TypeGuard
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import abc
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import textwrap
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import typing
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import weakref
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import types
@@ -2156,6 +2157,45 @@ def barfoo(x: AT): ...
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def barfoo2(x: CT): ...
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self.assertIs(get_type_hints(barfoo2, globals(), locals())['x'], CT)
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def test_generic_pep585_forward_ref(self):
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# See https://bugs.python.org/issue41370
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class C1:
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a: list['C1']
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self.assertEqual(
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get_type_hints(C1, globals(), locals()),
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{'a': list[C1]}
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)
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class C2:
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a: dict['C1', list[List[list['C2']]]]
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self.assertEqual(
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get_type_hints(C2, globals(), locals()),
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{'a': dict[C1, list[List[list[C2]]]]}
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)
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# Test stringified annotations
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scope = {}
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exec(textwrap.dedent('''
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from __future__ import annotations
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class C3:
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a: List[list["C2"]]
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'''), 8000 scope)
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C3 = scope['C3']
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self.assertEqual(C3.__annotations__['a'], "List[list['C2']]")
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self.assertEqual(
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get_type_hints(C3, globals(), locals()),
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{'a': List[list[C2]]}
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)
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# Test recursive types
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X = list["X"]
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def f(x: X): ...
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self.assertEqual(
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get_type_hints(f, globals(), locals()),
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{'x': list[list[ForwardRef('X')]]}
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)
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def test_extended_generic_rules_subclassing(self):
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class T1(Tuple[T, KT]): ...
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class T2(Tuple[T, ...]): ...
@@ -3556,15 +3596,15 @@ def foobar(x: list[ForwardRef('X')]): ...
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BA = Tuple[Annotated[T, (1, 0)], ...]
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def barfoo(x: BA): ...
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self.assertEqual(get_type_hints(barfoo, globals(), locals())['x'], Tuple[T, ...])
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self.assertIs(
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self.assertEqual(
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get_type_hints(barfoo, globals(), locals(), include_extras=True)['x'],
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BA
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)
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BA = tuple[Annotated[T, (1, 0)], ...]
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def barfoo(x: BA): ...
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self.assertEqual(get_type_hints(barfoo, globals(), locals())['x'], tuple[T, ...])
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self.assertIs(
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self.assertEqual(
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get_type_hints(barfoo, globals(), locals(), include_extras=True)['x'],
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BA
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)

‎Lib/typing.py

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -336,6 +336,12 @@ def _eval_type(t, globalns, localns, recursive_guard=frozenset()):
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if isinstance(t, ForwardRef):
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return t._evaluate(globalns, localns, recursive_guard)
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if isinstance(t, (_GenericAlias, GenericAlias, types.UnionType)):
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if isinstance(t, GenericAlias):
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args = tuple(
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ForwardRef(arg) if isinstance(arg, str) else arg
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for arg in t.__args__
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)
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t = t.__origin__[args]
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ev_args = tuple(_eval_type(a, globalns, localns, recursive_guard) for a in t.__args__)
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if ev_args == t.__args__:
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return t

‎Misc/NEWS.d/next/Library/2022-01-27-11-54-16.bpo-41370.gYxCPE.rst

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@@ -0,0 +1 @@
1+
:func:`typing.get_type_hints` now supports evaluating strings as forward references in :ref:`PEP 585 generic aliases <types-genericalias>`.

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