Fix version pattern pre-releases

[deathaxe]

This commit fixes a precedence issue with version pre-release tags.

Relational

The version module exports VERSION_PATTERN.

Directly using it, might not produce expected results for pre-releases.

>>> import re
>>> from packaging.version import VERSION_PATTERN

>>> re.match(VERSION_PATTERN, "1.0.0-alpha1")
<re.Match object; span=(0, 7), match='1.0.0-a'>

Trailing 1 from -alpha1 is not matched, because previous pattern preferred consuming only a instead of alpha due to missing word boundary checks.

Simplest solution is to re-order tokens, so regexp prefers longer tokens over their abbreviation.

>>> import re
>>> from packaging.version import VERSION_PATTERN

>>> re.match(VERSION_PATTERN, "1.0.0-alpha1")
<re.Match object; span=(0, 12), match='1.0.0-alpha1'>

Note: This commit also removes an unnecessary capture group.

[brettcannon]

Is there an open issue for this?

[uranusjr]

Since VERSION_PATTERN is marked as :meta hide-value: I don’t think you’re supposed to use it in the first place. An issue is defeinitely needed for discussion if you want to have a public value.

packaging/src/packaging/version.py

Lines 146 to 156 in 3030822

	VERSION_PATTERN = _VERSION_PATTERN
	"""
	A string containing the regular expression used to match a valid version.
	The pattern is not anchored at either end, and is intended for embedding in larger
	expressions (for example, matching a version number as part of a file name). The
	regular expression should be compiled with the ``re.VERBOSE`` and ``re.IGNORECASE``
	flags set.
	:meta hide-value:
	"""

[deathaxe]

A public value wouldn't have any value for me as I can't use this package anyway, due to the need of supporting python 3.3

I just stumbled about the pattern not doing what I expected without explicit anchors being added.

If the variable is not intented for public use, it should probably not be part of __all__.

[pradyunsg]

Seems like a reasonable fix to me.

[pradyunsg]

Since VERSION_PATTERN is marked as :meta hide-value: I don’t think you’re supposed to use it in the first place

It's a part of the public API, but we don't want the entire regex string to be presented in the documentation: https://packaging.pypa.io/en/stable/version.html#packaging.version.VERSION_PATTERN

[deathaxe]

An alternative would be to align the pattern with the ones from specifiers module.

packaging/src/packaging/specifiers.py

Line 154 in 3030822

(alpha|beta|preview|pre|a|b|c|rc)