setuptools 应该在 setup.cfg 文件的 setup_requires 条目中吗？

Question

importlib_resources backport for Python < 3.7 of the importlib.resources 标准库模块在 setup.cfg 文件中有以下部分：

[options]
python_requires = >=2.7,!=3.0,!=3.1,!=3.2,!=3.3
setup_requires =
    setuptools
    wheel
install_requires =
    pathlib2; python_version < '3'
    typing; python_version < '3.5'
packages = find:

为什么 setup_requires 包括 setuptools？这似乎没有意义，因为：

setup.py文件的第一行导入了setuptools，所以在调用setup函数并读取setup.cfg文件的时候指示安装 setuptools 安装已经太晚了 setuptools:
```
from setuptools import setup
setup()
```

setuptools 已经安装在任何新的 Python 安装上（好吧，只在 Windows 10 和 MacOS 10.15 上测试 Python 3.8。 0):

$ python -V
Python 3.8.0
$ pip list
Package    Version
---------- -------
pip        19.2.3
setuptools 41.2.0
WARNING: You are using pip version 19.2.3, however version 19.3.1 is available.
You should consider upgrading via the 'python -m pip install --upgrade pip' command.

Answer 1

Why does setup_requires includes setuptools? This does not seem to make sense

完全没有意义。另一方面，它不会妨碍任何事情，为什么不呢？

Answer 2

不，setuptools 不应包含在 setup_requires 中，根据 PEP 518（粗体强调我的）：

Setuptools tried to solve this with a setup_requires argument to its setup() function [3]. This solution has a number of issues, such as:

No tooling (besides setuptools itself) can access this information without executing the setup.py, but setup.py can't be executed without having these items installed.

While setuptools itself will install anything listed in this, they won't be installed until during the execution of the setup() function, which means that the only way to actually use anything added here is through increasingly complex machinations that delay the import and usage of these modules until later on in the execution of the setup() function.

This cannot include setuptools itself nor can it include a replacement to setuptools, which means that projects such as numpy.distutils are largely incapable of utilizing it and projects cannot take advantage of newer setuptools features until their users naturally upgrade the version of setuptools to a newer one.

The items listed in setup_requires get implicitly installed whenever you execute the setup.py but one of the common ways that the setup.py is executed is via another tool, such as pip, who is already managing dependencies. This means that a command like pip install spam might end up having both pip and setuptools downloading and installing packages and end users needing to configure both tools (and for setuptools without being in control of the invocation) to change settings like which repository it installs from. It also means that users need to be aware of the discovery rules for both tools, as one may support different package formats or determine the latest version differently.

Answer 3

接受的答案大部分是正确的，但 PEP 518 说的是。

[The setup_requires mechanism] cannot include setuptools itself...

它在技术上是不正确的，正如 importlib_resources 所证明的那样，它可以实际上包括 setuptools。问题是在 setup_requires 中包含 setuptools 主要用作文档。它声明 setuptools 是构建要求（运行 setup.py 需要），但如果尚未满足，它将无法满足该要求。

但是，setuptools 在 setup_requires 中的存在在技术上是正确的，并且确实起到了声明要求并要求安装工具验证要求实际上已安装的目的（以及其他安装-时间要求）。

然而，它只是一个遗留的工件，并没有提供那么多的价值，而且从问题和答案中可以看出，它确实会导致混淆。推荐的正确方法是使用 PEP 517 和 518 声明和构建器，但生态系统的那部分尚未成熟，因此 setuptools 遗迹将保留。尽量不要让他们打扰你。

setuptools 应该在 setup.cfg 文件的 setup_requires 条目中吗？

Should setuptools be in the setup_requires entry of setup.cfg files?

python

setuptools

python-wheel