ast.Constant.n deprecated without warning

[jwilk]

BPO	46797
Nosy	@jwilk, @serhiy-storchaka
PRs	gh-90953: Emit deprecation warnings for deprecated ast features #31432

^{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 = None
created_at = <Date 2022-02-19.08:29:16.968>
labels = ['library', '3.11']
title = 'ast.Constant.n deprecated without warning'
updated_at = <Date 2022-02-19.12:24:07.912>
user = 'https://github.com/jwilk'

bugs.python.org fields:

activity = <Date 2022-02-19.12:24:07.912>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2022-02-19.08:29:16.968>
creator = 'jwilk'
dependencies = []
files = []
hgrepos = []
issue_num = 46797
keywords = ['patch']
message_count = 2.0
messages = ['413541', '413546']
nosy_count = 2.0
nosy_names = ['jwilk', 'serhiy.storchaka']
pr_nums = ['31432']
priority = 'low'
resolution = 'postponed'
stage = 'patch review'
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue46797'
versions = ['Python 3.11']

Linked PRs

• gh-90953: Emit deprecation warnings for ast features deprecated in Python 3.8 #104199
• gh-90953: Don't use deprecated AST nodes in clinic.py #104322
• [3.9] gh-90953: Don't use deprecated AST nodes in clinic.py (GH-104322) #140854
• [3.10] gh-90953: Don't use deprecated AST nodes in clinic.py (GH-104322) #140855
• [3.11] gh-90953: Don't use deprecated AST nodes in clinic.py (GH-104322) #140856

[jwilk]

ast.Constant.n is documented to be deprecated, but you don't get any warning when you use it:

$ python3.11 -Wd
Python 3.11.0a5 (main, Feb 12 2022, 17:11:59) [GCC 9.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import ast
>>> help(ast.Constant.n)
Help on property:

Deprecated. Use value instead.

>>> ast.Constant(value=42).n
42

[serhiy-storchaka]

It is because we did not have a plan for removing deprecates features. Deprecation in documentation only helps third-party code. Instead of adding a complex code which switches between using old and new names depending on Python version, the third-party code can continue to use old names without worring about deprecation warnings, and switch completely to using new features only when support of old Python versions be dropped. 3.7 and 3.8 are not so old and may be still supported in third-party code.

I have created a PR which adds deprecation warnings, but I am not sure that it is worth to include it in 3.11.