形式“package===version"的setuptools要求的目的是什么? [英] What is the purpose of setuptools requirements of the form "package===version"

问题描述

假设我有一个带有控制台脚本的包，例如

Say I have a package with a console script such as

from setuptools import setup
setup(
    name='eg_package',
    version='0.0.1',
    description='Trivial test package',
    packages=[
       'eg_package',
    ],
    entry_points={
        'console_scripts': [
            'foo = eg_package.main:main',
        ]
   },
)

如果我使用 egg_info -b mytag 设置和显式构建标记，则生成的脚本具有 __requires__ = 'eg-package===0.0.1mytag'，即具有 3="符号.当标签不是 Beta 版的 b1 等传统标签时，就会发生这种情况.

If I set and explicit build tag using egg_info -b mytag the resulting script has __requires__ = 'eg-package===0.0.1mytag', i.e. with 3 "=" signs. This occurs when the tag is not something conventional like b1 for a beta release.

起初我认为这是一个错误，但 setuptools 文档表明它是一个有效的需求标识符.但是，它不适用于导致我们系统出现问题的旧版 setuptools.

At first I thought this was a bug but the setuptools documentation suggests it is a valid requirement identifier. However, it doesn't work with older versions of setuptools which is causing problems with our systems.

我的问题是 "===" 是什么意思，为什么现代 setuptools 使用它?

My question is what does "===" mean and why does modern setuptools use it?

推荐答案

pip 文档中的需求说明符部分 链接到 由setuptools pkg_resources 实现的需求说明符的官方文档.它指定了形式语法，但没有说明语义.概述文档解释语义，但在~= 和 === 显然是在 vv.7(安装 python 2.7.9)和 16 之间添加的东西.

Requirement specifier section in pip docs links to the official docs for requirement specifiers implemented by setuptools pkg_resources. It specifies the formal syntax but says nothing on the semantics. Overview docs explain semantics but say nothing on the ~= and === stuff that were apparently added somewhere between vv.7 (installed with python 2.7.9) and 16.

当文档失败时，是时候查阅来源了.下载 setuptools hg repo 并注释 pkg_resources/__init__.py 最终将我们带到变更集 3125 并带有消息Implement PEP 440" by using the Packaging library.

When docs fail, it's time to consult the sources. Downloading the setuptools hg repo and annotating pkg_resources/__init__.py ultimately brings us to changeset 3125 with the message "Implement PEP 440 by using the packaging library".

确实，PEP 440，版本说明符部分解释了语法和语义:

Indeed, PEP 440, Version Specifiers section explains the syntax and semantics:

• ~= : 兼容版本子句<...>
• === : 任意相等子句.

通过检查提交中的其他文件和相关的packaging 包，我得出了以下明显的结论:

By examining other files in the commit and the related packaging package, I came to these apparent conclusions:

• ~= 永远不会产生；当处理¹时，它根据 PEP 中概述的规则充当过滤器.
• ===，在处理时，会发出信号以回退到旧的 setuptools 版本语法和比较逻辑.只要生成的版本字符串不符合 PEP²，就会生成它.

• ~= is never produced; when handled¹, it acts as a filter according to the rules outlined in the PEP.
• ===, when handled, signals to fall back to the older setuptools version syntax and comparison logic. It is produced whenever the resulting version string doesn't conform to the PEP².

¹_{在 pkg_resources._vendor.packaging.specifiers._compare_compatible()} 中²_{pkg_resources.parse_version() 产生一个 pkg_resources.SetuptoolsLegacyVersion 而不是 pkg_resources.SetuptoolsVersion}

¹ _{In pkg_resources._vendor.packaging.specifiers._compare_compatible()} ²_{pkg_resources.parse_version() produces a pkg_resources.SetuptoolsLegacyVersion rather than pkg_resources.SetuptoolsVersion}

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