GeezerVison

Something feels off. Why did I ever care about setting this when configuring the host? If I remember correctly it was because tests failed using the host runner if I didn't via make test. But that doesn't seem right since that would mean a WASI build was somehow special in regards to paths compared to any other build which it shouldn't be. Plus if the python.sh shell script works which doesn't make the change to PYTHONPATH then it really feels weird that this is even here.

Can someone test what happens if you just take out the environment updates?

Yeah, that's right. I tested removing the environment updates. Without PYTHONPATH, tests fail with ModuleNotFoundError: No module named '_sysconfigdata__wasi_wasm32-wasi' (because this lives in the build dir and not in Lib/, I think).

python.sh does include PYTHONPATH. It's just passed in via --env in the wasmtime command.

Is this an out-of-tree build issue? I never bothered to figure out why this is an issue since you would think all builds have the same situation and yet none of us set it when we run the test suite from a checkout.

Yes, that is the case. However, after looking into this more, I think we can delete this entirely in favour of passing --argv0 to wasmtime. getpath.py reads pybuilddir.txt from the directory of the binary to auto-discover the sysconfig data directory, but without --argv0 the WASI guest receives the host path for argv[0] which doesn't resolve inside the guest filesystem. I tested this locally and everything built correctly/tests passed.

@therohityadav Did you want to try applying the approach I mentioned above? We should just be able to replace PYTHONPATH with ARGV0 here and the plumb it through in default_host_runner

I've opened a PR with this approach here: #145328