coverage run in isolated mode does not preserve sys.path correctly Python 3.10 #2103
Description
Describe the bug
When running coverage run with the -I flag (isolated mode) under Python 3.12, the initial sys.path differs from the behavior under Python 3.10.
Under Python 3.10 the current working directory is incorrectly included in sys.path.
The path entry sys.path[1] is unexpectedly removed instead of sys.path[0].
To Reproduce
$ cd /tmp
$ echo 'import sys;print("sys.flags:", sys.flags);print("sys.path:", sys.path)' > poc.py
$ python3.10 -m venv venv310
$ python3.12 -m venv venv312
$ ./venv310/bin/pip install coverage==7.12.0
$ ./venv312/bin/pip install coverage==7.12.0
$ ./venv310/bin/python3.10 -Im coverage run poc.py
sys.flags: sys.flags(debug=0, inspect=0, interactive=0, optimize=0, dont_write_bytecode=0, no_user_site=1, no_site=0, ignore_environment=1, verbose=0, bytes_warning=0, quiet=0, hash_randomization=1, isolated=1, dev_mode=False, utf8_mode=0, warn_default_encoding=0, int_max_str_digits=-1)
sys.path: ['/tmp', '/usr/lib/python3.10', '/usr/lib/python3.10/lib-dynload', '/tmp/venv310/lib/python3.10/site-packages']
$./venv312/bin/python3.12 -Im coverage run poc.py
sys.flags: sys.flags(debug=0, inspect=0, interactive=0, optimize=0, dont_write_bytecode=0, no_user_site=1, no_site=0, ignore_environment=1, verbose=0, bytes_warning=0, quiet=0, hash_randomization=1, isolated=1, dev_mode=False, utf8_mode=0, warn_default_encoding=0, safe_path=True, int_max_str_digits=4300)
sys.path: ['/usr/lib/python312.zip', '/usr/lib/python3.12', '/usr/lib/python3.12/lib-dynload', '/tmp/venv312/lib/python3.12/site-packages']
Answer the questions below:
-
What version of Python are you using?
python3.10 and python3.12 -
What version of coverage.py shows the problem? The output of
coverage debug sysis helpful.
./venv312/bin/python3.12 -m coverage debug sys
-- sys -------------------------------------------------------
coverage_version: 7.12.0
coverage_module: /tmp/venv312/lib/python3.12/site-packages/coverage/__init__.py
core: -none-
CTracer: available from /tmp/venv312/lib/python3.12/site-packages/coverage/tracer.cpython-312-x86_64-linux-gnu.so
plugins.file_tracers: -none-
plugins.configurers: -none-
plugins.context_switchers: -none-
configs_attempted: /tmp/.coveragerc
/tmp/setup.cfg
/tmp/tox.ini
/tmp/pyproject.toml
configs_read: -none-
config_file: None
config_contents: -none-
data_file: -none-
python: 3.12.7 (main, Oct 1 2024, 08:52:12) [GCC 11.4.0]
platform: Linux-6.8.0-45-generic-x86_64-with-glibc2.39
implementation: CPython
build: main
Oct 1 2024 08:52:12
gil_enabled: True
executable: /tmp/venv312/bin/python3.12
def_encoding: utf-8
fs_encoding: utf-8
pid: 12181
cwd: /tmp
path: /tmp
/usr/lib/python312.zip
/usr/lib/python3.12
/usr/lib/python3.12/lib-dynload
/tmp/venv312/lib/python3.12/site-packages
environment: HOME = /home/maillol
command_line: /tmp/venv312/lib/python3.12/site-packages/coverage/__main__.py debug sys
time: 2025-12-08 09:25:36
./venv310/bin/python3.10 -m coverage debug sys
-- sys -------------------------------------------------------
coverage_version: 7.12.0
coverage_module: /tmp/venv310/lib/python3.10/site-packages/coverage/__init__.py
core: -none-
CTracer: available from /tmp/venv310/lib/python3.10/site-packages/coverage/tracer.cpython-310-x86_64-linux-gnu.so
plugins.file_tracers: -none-
plugins.configurers: -none-
plugins.context_switchers: -none-
configs_attempted: /tmp/.coveragerc
/tmp/setup.cfg
/tmp/tox.ini
/tmp/pyproject.toml
configs_read: -none-
config_file: None
config_contents: -none-
data_file: -none-
python: 3.10.18 (main, Jun 4 2025, 08:56:00) [GCC 13.3.0]
platform: Linux-6.8.0-45-generic-x86_64-with-glibc2.39
implementation: CPython
build: main
Jun 4 2025 08:56:00
gil_enabled: True
executable: /tmp/venv310/bin/python3.10
def_encoding: utf-8
fs_encoding: utf-8
pid: 12199
cwd: /tmp
path: /tmp
/usr/lib/python310.zip
/usr/lib/python3.10
/usr/lib/python3.10/lib-dynload
/tmp/venv310/lib/python3.10/site-packages
environment: HOME = /home/maillol
command_line: /tmp/venv310/lib/python3.10/site-packages/coverage/__main__.py debug sys
time: 2025-12-08 09:25:45
Expected behavior
Under Python 3.10
sys.path: ['/usr/lib/python310.zip', '/usr/lib/python3.10', '/usr/lib/python3.10/lib-dynload', '/tmp/venv310/lib/python3.10/site-packages']
Additional context
The incorrect behavior under Python 3.10 seems to have been present since coverage 5.0.3.
This issue also appears related to how coverage.execfile.PyRunner handles the safe_path flag.
However, this flag does not exist in Python 3.10, which may contribute to the inconsistent behavior between Python 3.10 and Python 3.12.