[BUG] Restore support for newlines in Summary

[kiorky]

setuptools version

>=59

Python version

3.8

OS

linux

Additional environment information

No response

Description

 File "/code/venv/lib/python3.8/site-packages/setuptools/dist.py", line 151, in single_line
   raise ValueError('Newlines are not allowed')

reopening of #2893 which does not address correctly the issue introduced by #1390.

Expected behavior

Warning or nothing, just escape silently \n for oneline metadata fields

Lot of already released eggs wont ever comply to this policy, but we need to install them at the version they are pinned in our builds for the sake of reproducibility.

How to Reproduce

pip install django-hijack==2.1.10

see #2893 (comment)

Output

  ERROR: Command errored out with exit status 1:
   command: venv/bugpip/bin/python -c 'import io, os, sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-10qe4uxx/django-hijack_c7b8d72ff0ad41998610fe76e5822048/setup.py'"'"'; __file__='"'"'/tmp/pip-install-10qe4uxx/django-hijack_c7b8d72ff0ad41998610fe76e5822048/setup.py'"'"';f = getattr(tokenize, '"'"'open'"'"', open)(__file__) if os.path.exists(__file__) else io.StringIO('"'"'from setuptools import setup; setup()'"'"');code = f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' egg_info --egg-base /tmp/pip-pip-egg-info-awfzhldp
       cwd: /tmp/pip-install-10qe4uxx/django-hijack_c7b8d72ff0ad41998610fe76e5822048/
  Complete output (26 lines):
  running egg_info
  creating /tmp/pip-pip-egg-info-awfzhldp/django_hijack.egg-info
  writing /tmp/pip-pip-egg-info-awfzhldp/django_hijack.egg-info/PKG-INFO
  Traceback (most recent call last):
    File "<string>", line 1, in <module>
    File "/tmp/pip-install-10qe4uxx/django-hijack_c7b8d72ff0ad41998610fe76e5822048/setup.py", line 44, in <module>
      setup(name="django-hijack",
    File "venv/bugpip/lib/python3.8/site-packages/setuptools/__init__.py", line 153, in setup
      return distutils.core.setup(**attrs)
    File "/usr/lib/python3.8/distutils/core.py", line 148, in setup
      dist.run_commands()
    File "/usr/lib/python3.8/distutils/dist.py", line 966, in run_commands
      self.run_command(cmd)
    File "/usr/lib/python3.8/distutils/dist.py", line 985, in run_command
      cmd_obj.run()
    File "venv/bugpip/lib/python3.8/site-packages/setuptools/command/egg_info.py", line 292, in run
      writer(self, ep.name, os.path.join(self.egg_info, ep.name))
    File "venv/bugpip/lib/python3.8/site-packages/setuptools/command/egg_info.py", line 656, in write_pkg_info
      metadata.write_pkg_info(cmd.egg_info)
    File "/usr/lib/python3.8/distutils/dist.py", line 1117, in write_pkg_info
      self.write_pkg_file(pkg_info)
    File "venv/bugpip/lib/python3.8/site-packages/setuptools/dist.py", line 167, in write_pkg_file
      write_field('Summary', single_line(self.get_description()))
    File "venv/bugpip/lib/python3.8/site-packages/setuptools/dist.py", line 151, in single_line
      raise ValueError('Newlines are not allowed')
  ValueError: Newlines are not allowed

Code of Conduct

• I agree to follow the PSF Code of Conduct

[jaraco]

Please do not file duplicate issues.

[kiorky]

So please do not close not fixed bug.