[BUG] Failed to install pathlib: 'PosixPath' object has no attribute 'read_text'

[bartmao]

setuptools version

setuptools>=60.9.0

Python version

3.7

OS

Debian

Additional environment information

pip 22.0.3

Description

Failed to install pathlib in force mode

Expected behavior

pathlib successfully installed

How to Reproduce

pip install --force-reinstall  --no-cache-dir pathlib

Output

Defaulting to user installation because normal site-packages is not writeable
Collecting pathlib
  Downloading pathlib-1.0.1.tar.gz (49 kB)
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 49.3/49.3 KB 64.1 kB/s eta 0:00:00
  Preparing metadata (setup.py) ... error
  error: subprocess-exited-with-error
  
  × python setup.py egg_info did not run successfully.
  │ exit code: 1
  ╰─> [20 lines of output]
      Traceback (most recent call last):
        File "<string>", line 36, in <module>
        File "<pip-setuptools-caller>", line 34, in <module>
        File "/tmp/pip-install-um6pgzdc/pathlib_96ea0574b3694106a3e5ebed231d8a19/setup.py", line 30, in <module>
          url='https://pathlib.readthedocs.org/',
        File "/home/tiger/.local/lib/python3.7/site-packages/setuptools/_distutils/core.py", line 109, in setup
          _setup_distribution = dist = klass(attrs)
        File "/home/tiger/.local/lib/python3.7/site-packages/setuptools/dist.py", line 456, in __init__
          for ep in metadata.entry_points(group='distutils.setup_keywords'):
        File "/home/tiger/.local/lib/python3.7/site-packages/setuptools/_vendor/importlib_metadata/__init__.py", line 1003, in entry_points
          return SelectableGroups.load(eps).select(**params)
        File "/home/tiger/.local/lib/python3.7/site-packages/setuptools/_vendor/importlib_metadata/__init__.py", line 453, in load
          ordered = sorted(eps, key=by_group)
        File "/home/tiger/.local/lib/python3.7/site-packages/setuptools/_vendor/importlib_metadata/__init__.py", line 1001, in <genexpr>
          dist.entry_points for dist in unique(distributions())
        File "/home/tiger/.local/lib/python3.7/site-packages/setuptools/_vendor/importlib_metadata/__init__.py", line 613, in entry_points
          return EntryPoints._from_text_for(self.read_text('entry_points.txt'), self)
        File "/home/tiger/.local/lib/python3.7/site-packages/setuptools/_vendor/importlib_metadata/__init__.py", line 921, in read_text
          return self._path.joinpath(filename).read_text(encoding='utf-8')
      AttributeError: 'PosixPath' object has no attribute 'read_text'
      [end of output]

[abravalheri]

Hi @bartmao, I am under the impression that the package pathlib is discontinued and should not be used.

You can directly import pathlib in Python, because it is now part of the standard library. No need to install a third party package.

You can also install and use pathlib2 instead. (It should be a direct replacement).

---

The error is happening because by installing pathlib you are overwriting the implementation in the stdlib with some package that is not API-compatible. Therefore any code relying on the public/documented API of pathlib can break.

As a thought exercise you can think about a similar situation. Imagine you install a package in your environment that overwrites os and does not contain os.path.exists. Setuptools would also break in that situation because it relies on os.path.exists. There is nothing we can do in this case, since packages from the stdlib are supposed to be relied upon...

[edmorley]

The error is happening because by installing pathlib you are overwriting the implementation in the stdlib with some package that is not API-compatible. Therefore any code relying on the public/documented API of pathlib can break.

Hi! I don't believe this is correct.

Under a normally configured Python installation, the sys.path precedence is such that the Python stdlib comes before any site-packages directories. As such, the stdlib pathlib should "win" over any legacy installed pathlib package. Therefore whilst pathlib is not technically needed, it shouldn't cause problems if it's installed (such as being pulled in via third party deps which we may have no control over).

For example, using read_text() works just fine outside of setuptools, even if the legacy pathlib package is installed:

$ docker run --rm -it python:3.9.12 bash
root@d447c570719c:/# pip install pathlib==1.0.1
...
Successfully installed pathlib-1.0.1
root@d447c570719c:/# echo 'hello!' > testcase.txt
root@d447c570719c:/# python -c 'import pathlib; print(pathlib.PosixPath("testcase.txt").read_text())'
hello!

As such, this issue seems more like a setuptools bug, whereby the normal sys.path precedence is being overridden.

I've encountered something similar to that described here, but have opened a new issue since (a) the steps to reproduce are slightly different, (b) this issue is closed. See: #3294.

[abravalheri]

When installing pathlib, the deprecated/outdated/discouraged implementation in PyPI will be available as the first entry on sys.path, because of the way PYTHONPATH works (the current working dir is automatically added).

Isn't it the case?

[abravalheri]

We can think about the installation process for pathlib==1.0.1 as being roughly equivalent to:

cd /tmp
wget https://pypi.io/packages/source/p/pathlib/pathlib-1.0.1.tar.gz
tar xf pathlib-1.0.1.tar.gz
cd pathlib-1.0.1
python setup.py bdist_wheel  # suitable versions for both setuptools and wheel need to be installed
pip install dist/*.whl

The code running in the 5th line will try to load the pathlib from CWD, not from stdlib. If we replace the 5th, we can see that more clearly:

python -c 'import pathlib; print(pathlib)'
<module 'pathlib' from '/tmp/pathlib-1.0.1/pathlib.py'>

[edmorley]

Ah thank you for the explanation :-) I'll continue the conversation in #3294.