test_venv.test_special_chars_csh fails on NetBSD

[furkanonder]

Bug report

Bug description:

The test_venv.BasicTest.test_special_chars_csh test fails on NetBSD. NetBSD's csh cannot properly handle the specific character combination '";&&$e|"' even when correctly quoted, because $e is interpreted as a variable reference.

Configuration

./configure --with-pydebug

Test

home$ ./python -m test test_venv -m test_special_chars_csh -v
== CPython 3.15.0a0 free-threading build (heads/main:e8382e55c57, Sep 23 2025, 21:04:49) [GCC 10.5.0]
== NetBSD-10.1-amd64-x86_64-64bit-ELF little-endian
== Python build: free_threading debug
== cwd: /home/orange/cpython/build/test_python_worker_6821æ
== CPU count: 16
== encodings: locale=UTF-8 FS=utf-8
== resources: all test resources are disabled, use -u option to unskip tests

Using random seed: 3517063575
0:00:00 load avg: 0.08 Run 1 test sequentially in a single process
0:00:00 load avg: 0.08 [1/1] test_venv
test_special_chars_csh (test.test_venv.BasicTest.test_special_chars_csh)
Test that the template strings are quoted properly (csh) ... prompt: Undefined variable.

ERROR

======================================================================
ERROR: test_special_chars_csh (test.test_venv.BasicTest.test_special_chars_csh)
Test that the template strings are quoted properly (csh)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/orange/cpython/Lib/test/test_venv.py", line 544, in test_special_chars_csh
    out, err = check_output([csh, test_script])
               ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^
  File "/home/orange/cpython/Lib/test/test_venv.py", line 58, in check_output
    raise subprocess.CalledProcessError(
        p.returncode, cmd, out, err)
subprocess.CalledProcessError: Command '['/bin/csh', '/tmp/tmp82wovfyk/test_special_chars.csh']' returned non-zero exit status 1.

----------------------------------------------------------------------
Ran 1 test in 1.969s

FAILED (errors=1)
test test_venv failed
0:00:02 load avg: 0.15 [1/1/1] test_venv failed (1 error)

== Tests result: FAILURE ==

1 test failed:
    test_venv

Total duration: 2.3 sec
Total tests: run=1 (filtered)
Total test files: run=1/1 (filtered) failed=1
Result: FAILURE
home$

Reproduce

import os
import tempfile
import shutil
import subprocess
import shlex
from venv import EnvBuilder


def test_original_test_case():
    print("\n=== Reproducing original test case ===")

    csh = shutil.which('tcsh') or shutil.which('csh')
    if not csh:
        print("No csh/tcsh found, skipping test")
        return
    with tempfile.TemporaryDirectory() as tmpdir:
        env_name = '";&&$e|"'
        env_dir = os.path.join(os.path.realpath(tmpdir), env_name)
        try:
            builder = EnvBuilder(clear=True)
            builder.create(env_dir)
            activate = os.path.join(env_dir, 'bin', 'activate.csh')
            test_script = os.path.join(tmpdir, 'test_special_chars.csh')
            with open(test_script, "w") as f:
                f.write(f'source {shlex.quote(activate)}\n'
                        'python -c \'import sys; print(sys.executable)\'\n'
                        'python -c \'import os; print(os.environ["VIRTUAL_ENV"])\'\n'
                        'deactivate\n')
            print(f"\nRunning test script with {csh}:")
            try:
                result = subprocess.run([csh, test_script],
                                      capture_output=True, text=True, timeout=10)
                print(f"Return code: {result.returncode}")
                if result.returncode == 0:
                    print(f"Output: {result.stdout}")
                else:
                    print(f"Error: {result.stderr}")
            except Exception as e:
                print(f"Error running test: {e}")

        except Exception as e:
            print(f"Error in test case: {e}")


if __name__ == "__main__":
    test_original_test_case()

Output:

home: {5} ./python reproducer.py

=== Reproducing original test case ===

Running test script with /bin/csh:
Return code: 1
Error: prompt: Undefined variable.

home: {6} echo $SHELL
/bin/csh

# This FAILS with "Unmatched ." error
/bin/csh -c 'echo "Testing: \";&&$e|\""'

# This FAILS with "e: Undefined variable." error
/bin/csh -c 'echo "Testing: '\'';&&$e|'\''"'

# This WORKS correctly
/bin/csh -c 'echo '\''";&&$e|"'\'''

CPython versions tested on:

CPython main branch, 3.15, 3.14, 3.13

Operating systems tested on:

Other

Linked PRs

• gh-139308: Skip test_special_chars_csh on NetBSD due to csh variable expansion issue #139341
• [3.14] gh-139308: Skip test_special_chars_csh on NetBSD due to csh variable expansion issue (GH-139341) #139559
• [3.13] gh-139308: Skip test_special_chars_csh on NetBSD due to csh variable expansion issue (GH-139341) #139560

[furkanonder]

Based on the related NetBSD bug report #17826: {t,}csh backquote/braces expansion bug, which demonstrates that NetBSD's csh has issues with quote handling during expansion phases, I found a working approach:

# This works - uses single quotes around the entire string
/bin/csh -c 'echo '\''";&&$e|"'\'''

Why this works; PR #17826 revealed that NetBSD's csh expansion routines don't properly respect quote boundaries. The workaround above uses nested single quotes (''') to completely isolate the problematic string from any expansion phases, similar to the recommendations in that bug report.

I think we should skip this test on NetBSD.