The tested py.path.local.make_numbered_dir function is *not*
multiprocess safe, because is uses os.listdir which itself is not.
The os.listdir documentation explicitly states that:
> If a file is removed from or added to the directory during the call
> of this function, whether a name for that file be included is unspecified.
This can lead to a race when:
1. process A attempts to create directory N
2. the creation fails, as another process already created it in the meantime
3. process A calls listdir to determine a more recent maxnum
4. processes B+ repeatedly create newer directories and they delete directory N
5. process A doesn't have directory N or any newer directory in listdir result
6. process A attempts to create directory N again and raises
For details, see https://github.com/pytest-dev/pytest/issues/11603#issuecomment-1805708144
and bellow.
Additionally, the test itself has a race in batch_make_numbered_dirs.
When this functions attempts to write to repro-N/foo,
repro-N may have already been removed by another process.
For details, see https://github.com/pytest-dev/pytest/issues/11603#issuecomment-1804714313
and bellow.
---
The tested py.path.local.make_numbered_dir function is not used in pytest.
There is a different implementation in _pytest.pathlib.
Closes#11603
The current method as the following problem, described by Sadra
Barikbin:
The tests that request both `pytester` and `monkeypatch` and use
`monkeypatch.chdir` without context, relying on `monkeypatch`'s teardown
to restore cwd. This doesn't work because the following sequence of
actions take place:
- `monkeypatch` is set up.
- `pytester` is set up. It saves the original cwd and changes it to a
new one dedicated to the test function.
- Test function calls `monkeypatch.chdir()` without context.
`monkeypatch` saves cwd, which is not the original one, before
changing it.
- `pytester` is torn down. It restores the cwd to the original one.
- `monkeypatch` is torn down. It restores cwd to what it has saved.
The solution here is to have pytester use `monkeypatch.chdir()` itself,
then everything is handled correctly.
