doc: Add workaround for Cythonized code and pytest #293069
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@natsukium FYI. Let's get this knowledge into the documentation. |
sarahec
changed the title
Cython is a Python compiler that emits native .so modules. By default, python derivations run tests in the wrong directory to see these modules and tests fail. Issue #255262 documents the root cause and solution for this problem. This PR adds a description of the problem and the most common solution to the test troubleshooting list.
| @@ -2016,6 +2016,10 @@ example of such a situation is when `py.test` is used. | |||
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| * Tests that attempt to access `$HOME` can be fixed by using the following | |||
| work-around before running tests (e.g. `preCheck`): `export HOME=$(mktemp -d)` | |||
| * Compiling with Cython causes tests to fail with a `ModuleNotLoadedError`. | |||
| This can be fixed with two changes in the derivation: 1) replacing `pytest` with | |||
| `pytestCheckHook` and 2) adding a `preCheck` containing `cd $out` to run | |||
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Maybe cd / or something should be preferred because we really don't want to import anything that's not in $PYTHONPATH.
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I'm basing this on #255262 and the discussion there as well as fixing two packages' tests with this technique. If there's a better suggestion, I'm all ears.
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It's indeed important that whatever is installed takes precedence. In that sense, any folder but the source folder is good enough from that point of view. Then, comes the next, which @dotlambda mentions, we don't want to pick up anything more that we don't want either. Therefore, some folder where there is nothing of interest would be preferred.
Note it is also important to switch back directly again (assuming cd is used) for later phases/hooks.
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Hi folks, this PR has been open for a while but I don't know enough about the cython-related stuff to know whether this is mergeable in its current state or if it needs any changes. I'd like to help merge documentation PRs quicker as long as they're mergeable, can you help me decide whether this is the case here already? |
Cython is a Python compiler that emits native .so modules. By default, python derivations run tests in the wrong directory to see these modules and tests fail.
Issue #255262 documents the root cause and solution for this problem.
This PR adds a description of the problem and the most common solution to the test troubleshooting list.
Description of changes
Things done
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