unable to build as path dependency when build tool is not globally installed

[wobakj]

First, thanks for creating this package! It is super handy.

I would like to report a bug related to using py-build-cmake as build backend of a package a which is a local/path dependency for another package b with a build backend supporting PEP 508 path dependencies (e.g. poetry):

• During the pre-build phase of a, b is built to generate metadata.
• The build is done in a temp folder, and the build tool (e.g. ninja) is downloaded to there.
• For this for-metadata-build, the cmake cache is persistet in .py-build-cmake_cache in the package source folder of b.
• During the actually build process of a, the build of b fails because the cache references the build tool in the non-existent temp folder.

Proposed solutions:

• Create cmake cache not relative to source, but in package build folder.
• As workaround: Add a flag to disable the cmake cache.

[tttapa]

Thanks for the report!

Create cmake cache not relative to source, but in package build folder.

I'm afraid this kind of defeats the purpose of having a cache :)

As workaround: Add a flag to disable the cmake cache.

This is a good idea, I'll see if I can find some time to implement this soon.

As you've suggested in the title, the problem can be avoided by installing ninja globally (or in your current environment).
As a long-term solution, I believe py-build-cmake should keep track of whether it installed Ninja in a temporary folder or not, and clear the CMakeCache.txt file based on that.

[wobakj]

Thanks for the quick response! As alternative the long-term solution, maybe the ninja path variable can be make relative to the build folder/just contain the command? Then it should be valid regardless in which temp folder the build is taking place, because ninja is available in all cases.

[tttapa]

I have added a fix in 86dc912dbae9934f4841aabb3a0d06c5e6db49e9: If Ninja is installed in the current Python environment, its path is passed to CMake, updating the cache variable on every run.