bazelbuild
Stage-2 bootstrap script incorrectly removes inherited PYTHONPATH entries on Python 3.11 and above
🐞 bug report
Affected Rule
The issue is caused by the rule: py_binary / py_test
Is this a regression?
Yes.
Description
The stage-1 bootstrap script runs python with PYTHONSAFEPATH=1, which means that no unsafe paths are preprended to the runtime environment of stage-2.
However, the stage-2 script unconditionally deletes sys.path[0]. This is harmless most of the time, since the search path that is deleted is /usr/lib/python311.zip (or similar).
But if the target caller attempts to propagate PYTHONPATH to the application, the first entry in PYTHONPATH is incorrectly removed.
🔬 Minimal Reproduction
script.py:
import sys
print("\n".join(sys.path))
BUILD.bazel:
py_binary(
name = "script",
srcs = [":script.py"],
)
Build and run the target with PYTHONPATH=foo:bar, observe that foo is missing from sys.path.
🌍 Your Environment
Operating System:
Linux AMD64 - CentOS 7, and Debian 11
Output of bazel version:
Bazel 7.2.1
Rules_python version:
0.36.0 (but present in 0.37.0 too)
I suppose something is to be said about the smell that is attempting to set PYTHONPATH for a Bazel target.
Where I run into this problem is with VSCode/PyCharm debuggers which run their own bootstrap code via PYTHONPATH propagation, before running your actual target.
In any case, a simple fix for this is to replace this line, with:
if not getattr(sys.flags, "safe_path", False):
del sys.path[0]
Happy to raise a PR if agreed.
simple fix is to replace the del sys.path[0] line with guard
Yes. A PR for that would be approved.
