[Bug]: The tests parent directory (".") is added to the PYTHONPATH when using py_pytest_main

[keunhong]

What happened?

When using py_pytest_main the target's parent directory is added to the PYTHONPATH causing the same issues as in #368.

Version

Development (host) and target OS/architectures:

Output of bazel --version: bazel 8.0.0

Version of the Aspect rules, or other relevant rules from your
WORKSPACE or MODULE.bazel file:

bazel_dep(name = "rules_python", version = "1.0.0")
bazel_dep(name = "aspect_rules_py", version = "1.0.0", dev_dependency = True)

python_version = "3.10"
python = use_extension("@rules_python//python/extensions:python.bzl", "python")
python.toolchain(
    configure_coverage_tool = True,
    is_default = True,
    python_version = python_version,
)
use_repo(python, "python_3_10", "python_versions", "pythons_hub")

Language(s) and/or frameworks involved: python

How to reproduce

py_pytest_main(
    name = "__test__",
    deps = ["@pip//pytest"],
)

py_test(
    name = "my_test",
    srcs = ["my_test.py", "//:__test__"],
    main = "__test__.py",
    deps = [
        "//:__test__",
        "@pip//pytest",
    ],
)

If my_test.py has an import for e.g. concurrent.futures and there is a concurrent.py in the same directory it will cause a clash.

### Any other information?

_No response_

[keunhong]

This seems to be because pytest adds the test directory to sys.path through the mechanism described here: https://docs.pytest.org/en/latest/explanation/pythonpath.html#pythonpath

Setting --import-mode=append fixes this.

[alexeagle]

Cool, thanks for tracking down the culprit and a workaround. Do you think rules_py should include that flag for all users of py_pytest_main? Document its existence?

[keunhong]

Cool, thanks for tracking down the culprit and a workaround. Do you think rules_py should include that flag for all users of py_pytest_main? Document its existence?

I think append is a less surprising default, but I haven't considered all of the use cases. I think at least documenting it would be nice so no one has to go on a wild goose chase like I had to.