bpo-45166: fixes `get_type_hints` failure on `Final` (GH-28279)
Co-authored-by: Łukasz Langa <lukasz@langa.pl>
Co-authored-by: Ken Jin <28750310+Fidget-Spinner@users.noreply.github.com>
diff --git a/Lib/test/ann_module5.py b/Lib/test/ann_module5.py
new file mode 100644
index 0000000..837041e
--- /dev/null
+++ b/Lib/test/ann_module5.py
@@ -0,0 +1,10 @@
+# Used by test_typing to verify that Final wrapped in ForwardRef works.
+
+from __future__ import annotations
+
+from typing import Final
+
+name: Final[str] = "final"
+
+class MyClass:
+ value: Final = 3000
diff --git a/Lib/test/ann_module6.py b/Lib/test/ann_module6.py
new file mode 100644
index 0000000..6791756
--- /dev/null
+++ b/Lib/test/ann_module6.py
@@ -0,0 +1,7 @@
+# Tests that top-level ClassVar is not allowed
+
+from __future__ import annotations
+
+from typing import ClassVar
+
+wrong: ClassVar[int] = 1
diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
index fa49b90..d1887f7 100644
--- a/Lib/test/test_typing.py
+++ b/Lib/test/test_typing.py
@@ -2975,7 +2975,7 @@
# Definitions needed for features introduced in Python 3.6
-from test import ann_module, ann_module2, ann_module3
+from test import ann_module, ann_module2, ann_module3, ann_module5, ann_module6
from typing import AsyncContextManager
class A:
@@ -3339,6 +3339,22 @@
(Concatenate[int, P], int))
self.assertEqual(get_args(list | str), (list, str))
+ def test_forward_ref_and_final(self):
+ # https://bugs.python.org/issue45166
+ hints = get_type_hints(ann_module5)
+ self.assertEqual(hints, {'name': Final[str]})
+
+ hints = get_type_hints(ann_module5.MyClass)
+ self.assertEqual(hints, {'value': Final})
+
+ def test_top_level_class_var(self):
+ # https://bugs.python.org/issue45166
+ with self.assertRaisesRegex(
+ TypeError,
+ r'typing.ClassVar\[int\] is not valid as type argument',
+ ):
+ get_type_hints(ann_module6)
+
class CollectionsAbcTests(BaseTestCase):
diff --git a/Lib/typing.py b/Lib/typing.py
index e29d699..ada9adb 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -151,7 +151,7 @@
return arg
-def _type_check(arg, msg, is_argument=True, module=None):
+def _type_check(arg, msg, is_argument=True, module=None, *, is_class=False):
"""Check that the argument is a type, and return it (internal helper).
As a special case, accept None and return type(None) instead. Also wrap strings
@@ -164,14 +164,16 @@
We append the repr() of the actual value (truncated to 100 chars).
"""
invalid_generic_forms = (Generic, Protocol)
- if is_argument:
- invalid_generic_forms = invalid_generic_forms + (ClassVar, Final)
+ if not is_class:
+ invalid_generic_forms += (ClassVar,)
+ if is_argument:
+ invalid_generic_forms += (Final,)
arg = _type_convert(arg, module=module)
if (isinstance(arg, _GenericAlias) and
arg.__origin__ in invalid_generic_forms):
raise TypeError(f"{arg} is not valid as type argument")
- if arg in (Any, NoReturn):
+ if arg in (Any, NoReturn, Final):
return arg
if isinstance(arg, _SpecialForm) or arg in (Generic, Protocol):
raise TypeError(f"Plain {arg} is not valid as type argument")
@@ -662,9 +664,10 @@
__slots__ = ('__forward_arg__', '__forward_code__',
'__forward_evaluated__', '__forward_value__',
- '__forward_is_argument__', '__forward_module__')
+ '__forward_is_argument__', '__forward_is_class__',
+ '__forward_module__')
- def __init__(self, arg, is_argument=True, module=None):
+ def __init__(self, arg, is_argument=True, module=None, *, is_class=False):
if not isinstance(arg, str):
raise TypeError(f"Forward reference must be a string -- got {arg!r}")
try:
@@ -676,6 +679,7 @@
self.__forward_evaluated__ = False
self.__forward_value__ = None
self.__forward_is_argument__ = is_argument
+ self.__forward_is_class__ = is_class
self.__forward_module__ = module
def _evaluate(self, globalns, localns, recursive_guard):
@@ -692,10 +696,11 @@
globalns = getattr(
sys.modules.get(self.__forward_module__, None), '__dict__', globalns
)
- type_ =_type_check(
+ type_ = _type_check(
eval(self.__forward_code__, globalns, localns),
"Forward references must evaluate to types.",
is_argument=self.__forward_is_argument__,
+ is_class=self.__forward_is_class__,
)
self.__forward_value__ = _eval_type(
type_, globalns, localns, recursive_guard | {self.__forward_arg__}
@@ -1799,7 +1804,7 @@
if value is None:
value = type(None)
if isinstance(value, str):
- value = ForwardRef(value, is_argument=False)
+ value = ForwardRef(value, is_argument=False, is_class=True)
value = _eval_type(value, base_globals, base_locals)
hints[name] = value
return hints if include_extras else {k: _strip_annotations(t) for k, t in hints.items()}
@@ -1831,7 +1836,13 @@
if value is None:
value = type(None)
if isinstance(value, str):
- value = ForwardRef(value)
+ # class-level forward refs were handled above, this must be either
+ # a module-level annotation or a function argument annotation
+ value = ForwardRef(
+ value,
+ is_argument=not isinstance(obj, types.ModuleType),
+ is_class=False,
+ )
value = _eval_type(value, globalns, localns)
if name in defaults and defaults[name] is None:
value = Optional[value]
diff --git a/Misc/NEWS.d/next/Library/2021-09-10-21-35-53.bpo-45166.UHipXF.rst b/Misc/NEWS.d/next/Library/2021-09-10-21-35-53.bpo-45166.UHipXF.rst
new file mode 100644
index 0000000..b7242d4
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-09-10-21-35-53.bpo-45166.UHipXF.rst
@@ -0,0 +1,2 @@
+:func:`typing.get_type_hints` now works with :data:`~typing.Final` wrapped in
+:class:`~typing.ForwardRef`.
