VersionRange.invert() returns a complement that excludes versions outside an enumerated range

[sinagkh]

Summary

For vers:pypi/1.0.0|2.0.0, version 1.5.0 is outside both the original range and the result of invert(). This violates the documented inverse/complement purpose of the method and can leave versions unclassified when a caller partitions them using a range and its complement.

Reproduction

Save the following as repro.py.

from univers.version_range import VersionRange
from univers.versions import PypiVersion

r = VersionRange.from_string("vers:pypi/1.0.0|2.0.0")
inverse = r.invert()
print("range:", r)
print("inverse:", inverse)
for text in ("1.0.0", "1.5.0", "2.0.0"):
    v = PypiVersion(text)
    print(text, "in range:", v in r, "in inverse:", v in inverse)

Run:

python -m pip install univers==32.0.1
python repro.py

Actual result

range: vers:pypi/1.0.0|2.0.0
inverse: vers:pypi/!=1.0.0|!=2.0.0
1.0.0 in range: True in inverse: False
1.5.0 in range: False in inverse: False
2.0.0 in range: True in inverse: False

Expected result and contract

For each version, membership in a range and its complement should be opposite. In particular, 1.5.0 should be in the inverse because it is not in the original enumerated range; the two enumerated versions should remain outside the inverse.

The API's complement purpose is described in issue #91 and the implementing PR #92:
#91
#92

Code-level observation

invert() produces an all-!= constraint list. In the containment path, after testing the explicitly excluded versions, the =/!= constraints are filtered out and the empty remainder returns false. As a result, a version that matches none of the exclusions is still rejected. The report concerns the semantics of the returned complement, irrespective of how the constraint list's connective is represented internally.

I also reviewed the related containment issue #137; I could not establish that it covers this enumerated-inverse case:
#137

Environment

• Package: univers 32.0.1
• Runtime: CPython 3.13.3
• OS: macOS 26.6.2, Apple Silicon / arm64
• Reproduced: 2026-09-11

univers-reproduction.zip