Remove script dir from sys.path?

[robnagler]

Try this from any directory (not in sys.path):

echo 'import csv;csv.reader' > csv.py
python csv.py

It will give this error: AttributeError: module 'csv' has no attribute 'reader'

@garsuga ran into this error, and I was confused by it. I now see that sys.path gets PWD inserted. This broke @garsuga's code that we had to stop using the program, because sirepo.numpy exists. (The program cd'd to the module being debugged, which is a separate issue.)

I think we should consider dropping the first element in sys.path in pykern.pkcli. (We should also add a fixup to projex that imports everything unqualified to reduce [but not eliminate] collisions.)

This has been known in Unix since 1984.

Go recently added something to prevent this. I think this is a breaking change.

Since all processes are started with pykern.pkcli.main (except sirepo_jupyterhub which could be changed), it could strip '.' from the first element of sys.path. I think this would avoid problems and be more secure.

[e-carlin]

Sounds good. FWIW they've added a flag and env var in 3.11 python/cpython#31542

[robnagler]

Thanks for the link @e-carlin. It led me to _PyPathConfig_ComputeSysPath0, which computes syspath0. The function with documentation is 142 lines long. More importantly it uses readlink. Furthermore, py.test inserts pwd in sys.path. Kind of messy.