New test_site tests fail with `-s` interpreter flag

[itamaro]

Bug report

Bug description:

When running the test suite with the option to not add user site directory to sys.path (-s interpreter flag, or PYTHONNOUSERSITE=x env var), there are 5 new test failures from recently added test_site tests.

./python.exe -s -m test test_site -v
# or
PYTHONNOUSERSITE=x ./python.exe -m test test_site -v

Failing tests:

======================================================================
FAIL: test_base_arg (test.test_site.CommandLineTests.test_base_arg)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/itamaro/work/cpython/Lib/test/test_site.py", line 898, in test_base_arg
    self.assertEqual(return_code, excepted_return_code)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 0 != 1

======================================================================
FAIL: test_both_args (test.test_site.CommandLineTests.test_both_args)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/itamaro/work/cpython/Lib/test/test_site.py", line 915, in test_both_args
    self.assertEqual(return_code, excepted_return_code)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 0 != 1

======================================================================
FAIL: test_no_args (test.test_site.CommandLineTests.test_no_args)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/itamaro/work/cpython/Lib/test/test_site.py", line 884, in test_no_args
    self.assertEqual(lines[-1], f"ENABLE_USER_SITE: {site.ENABLE_USER_SITE}")
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 'ENABLE_USER_SITE: True' != 'ENABLE_USER_SITE: False'
- ENABLE_USER_SITE: True
?                   ^^^
+ ENABLE_USER_SITE: False
?                   ^^^^


======================================================================
FAIL: test_site_arg (test.test_site.CommandLineTests.test_site_arg)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/itamaro/work/cpython/Lib/test/test_site.py", line 906, in test_site_arg
    self.assertEqual(return_code, excepted_return_code)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 0 != 1

======================================================================
FAIL: test_underpth_no_user_site (test.test_site._pthFileTests.test_underpth_no_user_site)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/itamaro/work/cpython/Lib/test/test_site.py", line 814, in test_underpth_no_user_site
    self.assertEqual(p.returncode, 0, "sys.flags.no_user_site was 0")
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 1 != 0 : sys.flags.no_user_site was 0

These tests pass without the -s flag (or env var).

The failing tests seem to be testing specifically behavior around user site, so maybe that's expected? Should these tests skip if the "no user site" option is enabled for the test runner?

CPython versions tested on:

3.14, 3.15, CPython main branch

Operating systems tested on:

macOS, Linux

Linked PRs

• gh-140170: Fix test_site with -s flag #140179
• [3.14] gh-140170: Fix test_site with -s flag (GH-140179) #140198
• [3.13] gh-140170: Fix test_site with -s flag (GH-140179) #140201

[itamaro]

the new tests were added in gh-137428 and gh-133582

[ZeroIntensity]

I think the child process needs to inherit PYTHONUSERSITE here:

cpython/Lib/test/test_site.py

Lines 860 to 864 in bcced02

	with EnvironmentVarGuard() as env:
	env["PYTHONUTF8"] = "1"
	env["PYTHONIOENCODING"] = "utf-8"
	proc = spawn_python(*args, text=True, env=env,
	encoding='utf-8', errors='replace')

[itamaro]

I think the child process needs to inherit PYTHONUSERSITE here:

not sure what exactly you have in mind, but happy to try given a patch!
my blind attempts to set env["PYTHONNOUSERSITE"] before spawn_python didn't change anything for me

[StanFromIreland]

I wrote a fix in #140179.

[itamaro]

thank you @StanFromIreland !