Upper version bounds admit the next release's prereleases #189

#!/usr/bin/env python3
import json
import os
import shutil
import subprocess
import tempfile

# set up: PATH holds a CPython 3.12.0rc1 first, then the image's CPython 3.11.2
scene = tempfile.mkdtemp(prefix="pd-prerelease-")
prerelease_dir = os.path.join(scene, "prerelease")
stable_dir = os.path.join(scene, "stable")
empty_home = os.path.join(scene, "home")  # so no uv store under ~/.local/share/uv is searched
os.mkdir(prerelease_dir)
os.mkdir(stable_dir)
os.mkdir(empty_home)

# /tmp/repro.d is read-only and drops mode bits: copy the stand-in out and make it executable
rc_python = os.path.join(prerelease_dir, "python3.12")
shutil.copy("/tmp/repro.d/python3.12rc1_standin.py", rc_python)
os.chmod(rc_python, 0o755)
os.symlink("/usr/bin/python3.11", os.path.join(stable_dir, "python3.11"))
search_path = prerelease_dir + os.pathsep + stable_dir

# discover: three ranges that all stop before 3.12, each asked in a fresh process (discovery caches in-process)
picked = {}
for spec in (">=3.11,<3.12", ">=3.11,<3.12.0", "~=3.11.0"):
    caller = ["/opt/venv/bin/python", "/tmp/repro.d/find_interpreter.py", spec, search_path, empty_home]
    picked[spec] = json.loads(subprocess.run(caller, check=True, capture_output=True, text=True).stdout)
    print(f"{spec:16} -> {picked[spec]['version_info']}  {picked[spec]['executable']}")

# check: PEP 440 "<3.12.0" excludes 3.12.0rc1 and "~=3.11.0" means ==3.11.*, so all three must return 3.11.2
STABLE = [3, 11, 2, "final", 0]
RC = [3, 12, 0, "candidate", 1]
assert picked[">=3.11,<3.12"]["version_info"] == STABLE, "the '<3.12' spelling did not return 3.11.2: scene is broken"
rc_accepted = [spec for spec in (">=3.11,<3.12.0", "~=3.11.0") if picked[spec]["version_info"] == RC]
print("returned 3.12.0rc1 for:", rc_accepted)
print("BUG" if rc_accepted else "OK")

import json
import sys

from python_discovery import get_interpreter

spec, search_path, home = sys.argv[1:]
info = get_interpreter(spec, env={"PATH": search_path, "HOME": home})
print(json.dumps({"executable": info.executable, "version_info": list(info.version_info)}))

#!/usr/local/bin/python3.15
# The image has no pre-release build: the real 3.15 answers discovery's interrogation script
# with the version_info a CPython 3.12.0rc1 reports. Nothing else is changed.
import collections
import runpy
import sys

VersionInfo = collections.namedtuple("VersionInfo", "major minor micro releaselevel serial")
sys.version_info = VersionInfo(3, 12, 0, "candidate", 1)
# a real build reports its own path; left as python3.15, discovery would go on to probe that file instead
sys.executable = sys.argv[0]

interrogation_script = sys.argv[1]
sys.argv = sys.argv[1:]
runpy.run_path(interrogation_script, run_name="__main__")