Enable Scikit-Build-Core Support

[ahnaf-tahmid-chowdhury]

Description

This PR introduces support for scikit-build-core, streamlining the build process and improving compatibility.

This is a minimal version of the PR, excluding manylinux support, to facilitate a faster review. The full PR can be found here.

Key Changes

Enable scikit-build-core support

• Updated pyproject.toml to use scikit-build-core instead of legacy methods.

CMake and Build Updates

• Updated CMakeLists.txt to support skbuild, ensuring compatibility with both scikit-build-core and native CMake builds.
• Added GenerateScript.cmake to handle executable files (openmc) on both Linux and macOS.
• Updated OpenMCConfig.cmake.in to integrate scikit-build-core.

Git and Packaging Improvements

• Removed ignoring of .h5 files from .gitignore as they are needed.
• Removed MANIFEST.in as it is no longer required.

CI and Docs Updates

• Updated Dockerfile: Removed the need to run CMake before pip install as scikit-build-core now handles it.
• Updated CI configuration files to fix build and test issues.
• Added necessary APT packages for ReadTheDocs to compile dependencies properly.

Python API Enhancements

• Added functions to __init__.py to retrieve OpenMC installation configuration from the Python side.

Sponsored By

This contribution is kindly sponsored by @proximafusion, supporting the ongoing development and modernization of OpenMC’s Python packaging and build system.

[ahnaf-tahmid-chowdhury]

We need to do the same thing for mcpl that we have done for ncrystal.

[ahnaf-tahmid-chowdhury]

I have already created PR #3429 to make this PR working again.

[ahnaf-tahmid-chowdhury]

Everything is working now.

[nplinden]

Here's a minimal Dockerfile I used to produce the wheel for python 3.13/ubuntu25.04, works great:

FROM ubuntu:25.04

RUN apt update -y \
    && apt install -y python3 python-is-python3 python3-venv python3-dev \
                      git g++ cmake libhdf5-dev libpng-dev curl

RUN python -m venv venv \
    && . venv/bin/activate \
    && pip install git+https://github.com/ahnaf-tahmid-chowdhury/OpenMC.git@skbuild-minimal

What are the difficulties that need solving to add DAGMC+dependencies to the wheel?

[shimwell]

Glad to hear it is working for you.

What are the difficulties that need solving to add DAGMC+dependencies to the wheel?

No difficulties, Ahnaf and myself have already added DAGMC + Embree + Moab to a wheel. We have not included it in this PR as we are trying to keep it minimal. If this one is merged then we would follow up with a PR that adds DAGMC to the wheel. However for a sneak preview you could take a peak that this branch and this repo for method and resulting wheels. One difference is that we have used manylinux dockerfiles to ensure compatibility with other flavors of linux.

[shimwell]

Ah looks like the recent changes to the coverage need merging into this PR

CI error is
Run # Merge C++ and Python LCOV into a single file for upload
cat: coverage-cpp.lcov: No such file or directory

I think this is the PR that got the CI working again #3594

[ahnaf-tahmid-chowdhury]

Key things being changed, added, or removed:

• Build System Update: The pyproject.toml file is updated to use scikit-build-core as the build backend.
• CMake Build Updates:
  • CMakeLists.txt and related files have been adapted to support skbuild, ensuring compatibility with both scikit-build-core and regular CMake builds.
  • A new GenerateScript.cmake is added for handling executable files on Linux and macOS.
  • OpenMCConfig.cmake.in updated for integration with the new build system.
• Packaging & Project Files:
  • .gitignore is updated to stop ignoring .h5 files, as they are now required.
  • MANIFEST.in has been removed since it's no longer necessary.
• Continuous Integration & Documentation:
  • The Dockerfile is updated to give scikit-build-core responsibility for CMake steps.
  • Continuous integration and documentation build configs are updated to fix issues and ensure all dependencies are built properly.
  • Additional APT packages are added for ReadTheDocs builds.
• Python API Enhancements: Functions added to __init__.py to dynamically retrieve installation configuration details from Python.
• General Modernization: Old methods are deprecated/removed in favor of newer, streamlined approaches.

[ahnaf-tahmid-chowdhury]

This is just the foundation. More features will be added later, such as using CMake’s built-in modules for target generation, adding an openmc-config CLI, supporting manylinux images for PyPI, and improving the handling of external packages.

[GuySten]

This looks good to me.

[paulromano]

Putting a placeholder as I'd like to review this before we merge

[GuySten]

I noticed that the cpp test suite does not run.