Current PY_VERSION 3.10.0a7+ does not conform to PEP 440

[jouve]

BPO	44000
Nosy	@ned-deily, @ambv, @JelleZijlstra, @jouve, @pablogsal

^{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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assignee = None
closed_at = <Date 2021-05-01.17:59:25.275>
created_at = <Date 2021-05-01.17:06:30.701>
labels = []
title = 'Current PY_VERSION 3.10.0a7+ does not conform to PEP 440'
updated_at = <Date 2021-05-01.17:59:25.275>
user = 'https://github.com/jouve'

bugs.python.org fields:

activity = <Date 2021-05-01.17:59:25.275>
actor = 'Cyril Jouve'
assignee = 'none'
closed = True
closed_date = <Date 2021-05-01.17:59:25.275>
closer = 'Cyril Jouve'
components = []
creation = <Date 2021-05-01.17:06:30.701>
creator = 'Cyril Jouve'
dependencies = []
files = []
hgrepos = []
issue_num = 44000
keywords = []
message_count = 3.0
messages = ['392607', '392609', '392613']
nosy_count = 5.0
nosy_names = ['ned.deily', 'lukasz.langa', 'JelleZijlstra', 'Cyril Jouve', 'pablogsal']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue44000'
versions = []

[jouve]

It was changed from 3.10.0a7 to 3.10.0a7+ in
04eecf7

According to https://www.python.org/dev/peps/pep-0440/#public-version-identifiers, it should be something like 3.10.0a7.post1

or with https://www.python.org/dev/peps/pep-0440/#local-version-identifiers, it should be something like 3.10.0a7+post

see also implementation in packaging: https://github.com/pypa/packaging/blob/main/packaging/version.py#L225

[JelleZijlstra]

PEP-440 applies to Python packages, not to CPython itself. The "+" convention has been used in CPython for a long time, and changing it without a strong justification seems risky.

[jouve]

sure, I'll raise the issue with poetry then.

[radoering]

The "+" convention has been used in CPython for a long time, and changing it without a strong justification seems risky.

It might not be a strong justification but at least an argument:

According to PEP 508 python_full_version is equal to platform.python_version(). Although I could not find a direct reference, the sample values for python_full_version in PEP 508 seem to indicate that it should be PEP 440 compliant.

However, there is an escape hatch for non-compliant versions:

The <version_cmp> operators use the PEP 440 version comparison rules when those are defined (that is when both sides have a valid version specifier). If there is no defined PEP 440 behaviour and the operator exists in Python, then the operator falls back to the Python behaviour.

So far, so good.

However, if I'm right that implies a marker like python_full_version >= "3.9.0" is fulfilled for Python 3.10.0, but not for Python 3.10.0+. (IIUC, a version comparison should be used for the first one and a string comparison for the second one.)