On 2018-09-12 07:42, Simon King wrote:
However, the place in #25090/#25091 where the author uses is_package_installed, is a Python file.
Why does a Python file care whether the normaliz library and headers are installed? Now I'm looking at #25091 and it seems to me (but correct me if I'm wrong) that you *really* care about the PyNormaliz Python module, for which there is a different feature test.
The whole idea of the new features framework is to make the feature test as close as possible to the actual usage of the feature. We don't check for the presence of a Sage package, we check whatever feature that you need from that Sage package. For example, if it's a Python module, we try to import it.
Another way of seeing this: ask the question what would go wrong if the package wasn't installed but we skipped the feature check? That thing where it goes wrong is what you need to test for.
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