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ForwardRef does not support | operator #89652
Description
| BPO | 45489 |
|---|---|
| Nosy | @gvanrossum, @corona10, @Fidget-Spinner, @partiallyderived |
| PRs |
Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.
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GitHub fields:
assignee = None
closed_at = <Date 2021-10-16.15:43:32.751>
created_at = <Date 2021-10-15.16:37:31.685>
labels = ['type-bug', '3.11']
title = 'ForwardRef does not support | operator'
updated_at = <Date 2021-10-16.15:43:32.750>
user = 'https://github.com/partiallyderived'bugs.python.org fields:
activity = <Date 2021-10-16.15:43:32.750>
actor = 'kj'
assignee = 'none'
closed = True
closed_date = <Date 2021-10-16.15:43:32.751>
closer = 'kj'
components = []
creation = <Date 2021-10-15.16:37:31.685>
creator = 'bobbeyreese'
dependencies = []
files = []
hgrepos = []
issue_num = 45489
keywords = ['patch']
message_count = 8.0
messages = ['404037', '404078', '404084', '404085', '404086', '404087', '404090', '404091']
nosy_count = 4.0
nosy_names = ['gvanrossum', 'corona10', 'kj', 'bobbeyreese']
pr_nums = ['28991']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue45489'
versions = ['Python 3.11']
Activity
partiallyderived commentedon Oct 15, 2021
Not positive this is a bug, but it seems like ForwardRef should support the pipe (|) operator for indicating Unions in Python 3.10:
corona10 commentedon Oct 16, 2021
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -719,6 +719,12 @@ def __eq__(self, other):
def __hash__(self):
return hash(self.__forward_arg__)
+ def __or__(self, other):
+ return Union[self, other]
+
+ def __ror__(self, other):
+ return Union[other, self]
+
def __repr__(self):
return f'ForwardRef({self.__forward_arg__!r})'
This can be easily fixed, but I am waiting for guido and ken to check whether this is an intentioned operation.
gvanrossum commentedon Oct 16, 2021
I suppose this is useful for programs that use runtime annotations (e.g. pydantic?). I don’t mind adding this.
Fidget-Spinner commentedon Oct 16, 2021
ForwardRef is for internal use, and writing ForwardRef('fdsa') is discouraged, as the docs say:
This class should not be instantiated by a user.
However, I don't see any cons from adding union support, so let's do it!
Note that a workaround exists for OP's example. But it may not be sufficient for complex runtime libraries:
corona10 commentedon Oct 16, 2021
New changeset 15ad52f by Dong-hee Na in branch 'main':
bpo-45489: Update ForwardRef to support | operator. (GH-28991)
15ad52f
corona10 commentedon Oct 16, 2021
@guido
Do we need to create a backport for 3.10?
Ken and I are waiting for your comment :)
#28991 (comment)
gvanrossum commentedon Oct 16, 2021
No. :-)
Fidget-Spinner commentedon Oct 16, 2021
Thanks @corona10 for the patch.
@bobbeyreese
The new behavior is available in 3.11 and up. 3.10.x won't be supporting the | operator.