Pants doesn't detect sources roots unless root_pattern=["/"]

[mnowotnik]

Describe the bug
On MacOS root_pattern needs to be set to ["/"]. Any other value causes "No source root found for '.'" error.

Pants version
2.23.0

OS
MacOS

Additional info
/src/foo_lib/BUILD

python_sources(
    name="foo_lib",
    sources=["foo.py"],  # Include only source files
)

python_tests(
    name="foo_lib_tests",
    dependencies=[":foo_lib"],  # Test depends on the library
    sources=["test_foo.py"],    # Include only test files
)

/pants.toml

[GLOBAL]
pants_version = "2.23.0"
backend_packages = [
    "pants.backend.python",
    "pants.backend.docker",
    "pants.backend.shell",
    "pants.backend.experimental.python.lint.ruff.check"
]

[python]
interpreter_constraints = [">=3.7"]


[source]
root_patterns = ["/src"]

/BUILD

shell_sources(
    name="0",
)
python_sources(
    name="root",
)

Works without an issue if root_patterns = ["/"].

[mnowotnik]

No issue on Pop_OS Linux

[huonw]

Sorry for the trouble. Could you make a fully standalone reproducer for the issue you're seeing?

For instance, a git repo we can clone and execute ourselves, or a script like the one in #21228?

[mnowotnik]

@huonw So I made a repo and couldn't reproduce this. BUT I noticed that it fails if there's any Python file (matching *.py) in the project's root directory. If I remove it, suddenly everything works. Is it intended?

[huonw]

Ah, I think every python script is expected to have a source-root that includes it.

So, maybe root_patterns = ["/src", "/"] would be desirable, to cover the "normal" files in src as well as any top-level scripts. Does that help?

That said, it's peculiar that this behaviour would differ on different platforms.

(Thanks for waiting)