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gh-144533: Use pybuilddir.txt to find _sysconfigdata for WASI#144535
gh-144533: Use pybuilddir.txt to find _sysconfigdata for WASI#144535therohityadav wants to merge 1 commit intopython:mainfrom
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python-cla-botbot commentedFeb 6, 2026 • edited
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Platforms/WASI/__main__.py Outdated
| with pybuilddir.open("r", encoding="utf-8") as f: | ||
| sysconfig_data_dir = f"{wasi_build_dir}/{f.read().strip()}" | ||
| else: | ||
| # Fallback if the build hasn't generated the file yet |
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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 viamake 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 thepython.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?
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Yeah, that's right. I tested removing the environment updates. Without PYTHONPATH, tests fail withModuleNotFoundError: 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.
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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.
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Yes, that is the case. However, after looking into this more, I think we can deletethis entirely in favour of passing--argv0 to wasmtime.getpath.py readspybuilddir.txt from the directory of the binary to auto-discover the sysconfig data directory, but without--argv0 the WASI guest receives the host path forargv[0] which doesn't resolve inside the guest filesystem. I tested this locally and everything built correctly/tests passed.
savannahostrowskiFeb 20, 2026 • edited
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@therohityadav Did you want to try applying the approach I mentioned above? We should just be able to replacePYTHONPATH with ARGV0here and the plumb it through indefault_host_runner
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I've opened a PR with this approach here:#145328
b64935a to0ecc19eComparesavannahostrowski commentedFeb 28, 2026
Hey there - thanks so much for working on this. However, based on the earlier discussion (#144535 (comment)), I've just merged a PR with a different approach so I'll close this. |
_sysconfigdatafor the WASI build script #144533Use
pybuilddir.txtto find_sysconfigdatafor the WASI build script.The previous implementation hardcoded the path pattern to
build/lib.wasi-wasm32-{python_version}. This change makes the script more robust by reading the exact build directory frompybuilddir.txtif it exists. It falls back to the hardcoded path if the file is missing to ensure backward compatibility during early build stages.