Python context manager that backs up and restores `cwd` leaves terminal in erroneous state

Question

I have a context manager that temporarily backs up a directory and restores it upon exit. Here's the implementation:

import shutil
import tempfile
from pathlib import Path
from contextlib import contextmanager


@contextmanager
def on_exit(directory: Path):
    backup = Path(tempfile.mkdtemp(prefix="backup_")) / directory.name
    shutil.copytree(directory, backup, symlinks=True)
    try:
        yield
    finally:
        shutil.rmtree(directory)
        shutil.copytree(backup, directory, symlinks=True)
        shutil.rmtree(backup)

Here's a test that uses the context manager:

from pathlib import Path

from src.utils import rollback


def get_repo_root() -> Path:
    current_dir = Path(__file__).resolve()
    while current_dir != current_dir.parent:
        if (current_dir / ".git").exists():
            return current_dir
        current_dir = current_dir.parent
    raise RuntimeError("No repository root found.")


def test_rollback_on_exit():
    with rollback.on_exit(get_repo_root()):
        ...

• The directory is the root directory of my project, and I run pytest from this directory.
• The test passes, but my terminal ends up in an inconsistent state after execution. For example, after running the test, I see this behavior:

(dummy-py3.12) user@laptop ~/p/dummy (feat/rollback)> echo $PWD
/home/user/projects/dummy
(dummy-py3.12) user@laptop ~/p/dummy (feat/rollback)> echo $VIRTUAL_ENV
/home/user/.cache/pypoetry/virtualenvs/dummy-83ZLFGNe-py3.12
(dummy-py3.12) user@laptop ~/p/dummy (feat/rollback)> ls -la | wc -l
17
(dummy-py3.12) user@laptop ~/p/dummy (feat/rollback)> pytest tests/test_rollback.py
============================================= test session starts ==============================================
platform linux -- Python 3.12.3, pytest-7.2.1, pluggy-1.5.0
rootdir: /home/user/projects/dummy
plugins: cov-6.0.0, asyncio-0.21.1, typeguard-4.4.1, hypothesis-6.119.3
asyncio: mode=Mode.STRICT
collected 1 item                                                                                               

tests/test_rollback.py .                                                                          [100%]

=============================================== warnings summary ===============================================
tests/test_rollback.py: 20 warnings
  /home/user/.cache/pypoetry/virtualenvs/dummy-83ZLFGNe-py3.12/lib/python3.12/site-packages/typer/core.py:300: DeprecationWarning: 'autocompletion' is renamed to 'shell_complete'. The old name is deprecated and will be removed in Click 8.1. See the docs about 'Parameter' for information about new behavior.
    _typer_param_setup_autocompletion_compat(self, autocompletion=autocompletion)

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
======================================== 1 passed, 20 warnings in 0.74s ========================================
(dummy-py3.12) user@laptop ~/p/dummy (feat/rollback)> echo $PWD
/home/user/projects/dummy
(dummy-py3.12) user@laptop ~/p/dummy (feat/rollback)> echo $VIRTUAL_ENV
/home/user/.cache/pypoetry/virtualenvs/dummy-83ZLFGNe-py3.12
(dummy-py3.12) user@laptop ~/p/dummy> ls -la | wc -l
1
(dummy-py3.12) user@laptop ~/p/dummy> cd . 
(dummy-py3.12) user@laptop ~/p/dummy (feat/rollback)> ls -la | wc -l
17

The directory appears empty until I run cd . to "refresh" it.

Additional Observations

• This issue affects more than pytest. For example, running source ~/.config/fish/config.fish after the test produces similar errors (getcwd: cannot access parent directories).
• $PWD and $VIRTUAL_ENV remain unchanged before and after the test, suggesting the virtual environment itself is not the issue.

Debugging attempt:

I tried modifying the context manager to change the working directory before removing/restoring the original directory:

@contextmanager
def change_dir(target_path):
    original_path = Path.cwd()
    try:
        os.chdir(target_path)
        yield
    finally:
        os.chdir(original_path)


@contextmanager
def on_exit(directory: Path):
    backup = Path(tempfile.mkdtemp(prefix="backup_")) / directory.name
    shutil.copytree(directory, backup, symlinks=True)
    try:
        yield
    finally:
        with change_dir("/"):
            shutil.rmtree(directory)
            shutil.copytree(backup, directory, symlinks=True)
            shutil.rmtree(backup)

While this also passes the test, the terminal state is still inconsistent after execution. I must manually refresh it (cd .) to resolve the issue just the same.

Questions:

• Why does this happen? Is it related to the shell, pytest, or the virtual environment?
• How can I modify my context manager or testing setup to ensure the terminal state is fully restored after the test?

Update:

• the change_dir before removing and replacing the repository does work, without it the state after running tests is not properly reset and other tests are affected and fail.
• I tried running from a bash script, to no avail
• I tried running it in a subshell, to no avail
• I tried using pytest finalizers, to no avail

Answer 1

If you are removing and replacing the "current directory" (that is, "."), then this is expected. The shell knows your "current directory" by its inode number, not by its path. When you remove that directory, the inode points into empty space. Even though you create a new ".", that "." has a new inode number. The shell has cached the old one. The "cd ." fixes this.