Regression in 2.4.2: sdist install fails as root on Python < 3.10.12 / < 3.11.4 with TypeError: getgrnam() argument 'name' must be str, not None

[Pandorin]

Description

Since 2.4.2, poetry install fails as root while extracting an sdist on Pythons whose tarfile has no data_filter. We hit it in a Docker build on python:3.10.4-bullseye with crontab 1.0.4, facepy 1.0.12 and PyMeeus 0.5.12, which have no wheel on PyPI.

On these Pythons extractall() in poetry/utils/helpers.py uses the ported CPython 3.14 data filter added in #11027. The filter sets uid, gid, uname and gname to None, and members are then extracted with archive.extract(member, dest, set_attrs=not member.isdir()). As root, tarfile._extract_member() calls chown(), where these Python versions have no None guard:

# CPython 3.10.11, tarfile.py
try:
    if grp:
        g = grp.getgrnam(tarinfo.gname)[2]
except KeyError:
    pass

grp.getgrnam(None) raises TypeError, which is not caught, and the install aborts. CPython has if grp and tarinfo.gname: there from 3.10.12 and 3.11.4 on.

Checked with the same command, poetry install --no-root of crontab==1.0.4 as root:

Python	poetry 2.4.2	poetry 2.4.1
3.10.4	fails	ok
3.10.11	fails	not checked
3.10.12	ok	not checked
3.11.3	fails	not checked
3.11.4	ok	not checked
3.10.18	ok	not checked

In 2.4.1 the same fallback branch validated member paths only and did not change ownership attributes.

Reproduction

$ docker run --rm -u root python:3.10.4-bullseye bash -c '
  pip install -q "poetry==2.4.2"
  mkdir /t && cd /t
  printf "[project]\nname=\"repro\"\nversion=\"0.1.0\"\nrequires-python=\">=3.10\"\ndependencies=[\"crontab==1.0.4\"]\n" > pyproject.toml
  POETRY_VIRTUALENVS_CREATE=false poetry install --no-root'

The same command with poetry==2.4.1 succeeds.

Workarounds

• Run the install as a non-root user, verified on python:3.10.4-bullseye with 2.4.2.
• Use Python 3.10.12+ or 3.11.4+, verified above.
• Pin poetry==2.4.1.

Poetry Installation Method: pip

Operating System: Debian 11 (python:3.10.4-bullseye container), also seen on GitHub Actions ubuntu-24.04

Poetry Version: 2.4.2

Poetry Configuration

cache-dir = "/root/.cache/pypoetry"
installer.max-workers = null
installer.no-binary = null
installer.only-binary = null
installer.parallel = true
installer.re-resolve = false
solver.lazy-wheel = true
virtualenvs.create = false

Poetry Runtime Logs

poetry-runtime.log

5  poetry/installation/chef.py:60 in prepare
     →  60│         return self._prepare_sdist(
4  poetry/installation/chef.py:106 in _prepare_sdist
     → 106│             extractall(source=archive, dest=archive_dir, zip=zip)
3  poetry/utils/helpers.py:529 in extractall
     → 529│                     archive.extract(member, dest, set_attrs=not member.isdir())
2  /usr/local/lib/python3.10/tarfile.py:2090 in extract
     → 2090│             self._extract_member(tarinfo, os.path.join(path, tarinfo.name),
1  /usr/local/lib/python3.10/tarfile.py:2178 in _extract_member
     → 2178│             self.chown(tarinfo, targetpath, numeric_owner)

TypeError
getgrnam() argument 'name' must be str, not None
at /usr/local/lib/python3.10/tarfile.py:2284 in chown
    2283│                     if grp:
  → 2284│                         g = grp.getgrnam(tarinfo.gname)[2]
Cannot install crontab.