mirrors/cpython
1
0
Fork 0
mirror of https://github.com/python/cpython.git synced 2025-09-26 18:29:57 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 10

gh-133960: Improve typing.evaluate_forward_ref (#133961)

Browse source 
As explained in #133960, this removes most of the behavior differences with ForwardRef.evaluate.
The remaining difference is about recursive evaluation of forwardrefs; this is practically useful
in cases where an annotation refers to a type alias that itself is string-valued.

This also improves several edge cases that were previously not handled optimally. For example,
the function now takes advantage of the partial evaluation behavior of ForwardRef.evaluate() to
evaluate more ForwardRefs in the FORWARDREF format.

This also fixes #133959 as a side effect, because the buggy behavior in #133959 derives from
evaluate_forward_ref().
This commit is contained in:
Jelle Zijlstra 2025-05-25 10:26:39 -07:00 • committed by GitHub
parent b51b08a0a5
commit 57fef27cfc
No known key found for this signature in database
GPG key ID: B5690EEEBB952194
4 changed files with 132 additions and 56 deletions
Download patch file Download diff file Expand all files Collapse all files

50
Lib/typing.py
View file

@ -956,12 +956,8 @@ def evaluate_forward_ref(
"""Evaluate a forward reference as a type hint.
This is similar to calling the ForwardRef.evaluate() method,
but unlike that method, evaluate_forward_ref() also:
* Recursively evaluates forward references nested within the type hint.
* Rejects certain objects that are not valid type hints.
* Replaces type hints that evaluate to None with types.NoneType.
* Supports the *FORWARDREF* and *STRING* formats.
but unlike that method, evaluate_forward_ref() also
recursively evaluates forward references nested within the type hint.
*forward_ref* must be an instance of ForwardRef. *owner*, if given,
should be the object that holds the annotations that the forward reference
@ -981,23 +977,24 @@ def evaluate_forward_ref(
if forward_ref.__forward_arg__ in _recursive_guard:
return forward_ref
try:
value = forward_ref.evaluate(globals=globals, locals=locals,
type_params=type_params, owner=owner)
except NameError:
if format == _lazy_annotationlib.Format.FORWARDREF:
return forward_ref
else:
raise
if format is None:
format = _lazy_annotationlib.Format.VALUE
value = forward_ref.evaluate(globals=globals, locals=locals,
type_params=type_params, owner=owner, format=format)
type_ = _type_check(
value,
"Forward references must evaluate to types.",
is_argument=forward_ref.__forward_is_argument__,
allow_special_forms=forward_ref.__forward_is_class__,
)
if (isinstance(value, _lazy_annotationlib.ForwardRef)
and format == _lazy_annotationlib.Format.FORWARDREF):
return value
if isinstance(value, str):
value = _make_forward_ref(value, module=forward_ref.__forward_module__,
owner=owner or forward_ref.__owner__,
is_argument=forward_ref.__forward_is_argument__,
is_class=forward_ref.__forward_is_class__)
if owner is None:
owner = forward_ref.__owner__
return _eval_type(
type_,
value,
globals,
locals,
type_params,
@ -2338,12 +2335,12 @@ def get_type_hints(obj, globalns=None, localns=None, include_extras=False,
# This only affects ForwardRefs.
base_globals, base_locals = base_locals, base_globals
for name, value in ann.items():
if value is None:
value = type(None)
if isinstance(value, str):
value = _make_forward_ref(value, is_argument=False, is_class=True)
value = _eval_type(value, base_globals, base_locals, base.__type_params__,
format=format, owner=obj)
if value is None:
value = type(None)
hints[name] = value
if include_extras or format == Format.STRING:
return hints
@ -2377,8 +2374,6 @@ def get_type_hints(obj, globalns=None, localns=None, include_extras=False,
localns = globalns
type_params = getattr(obj, "__type_params__", ())
for name, value in hints.items():
if value is None:
value = type(None)
if isinstance(value, str):
# class-level forward refs were handled above, this must be either
# a module-level annotation or a function argument annotation
@ -2387,7 +2382,10 @@ def get_type_hints(obj, globalns=None, localns=None, include_extras=False,
is_argument=not isinstance(obj, types.ModuleType),
is_class=False,
)
hints[name] = _eval_type(value, globalns, localns, type_params, format=format, owner=obj)
value = _eval_type(value, globalns, localns, type_params, format=format, owner=obj)
if value is None:
value = type(None)
hints[name] = value
return hints if include_extras else {k: _strip_annotations(t) for k, t in hints.items()}