ephem package fails to install correctly for non-x86 architectures

[felddy]

🐛 Summary

The ephem Python package does not install correctly for non-x86 architectures (e.g., arm64, arm/v6, arm/v7, ppc64le, s390x) when building the WeeWX Docker container. This issue occurs because the package relies on a compiled C extension (_libastro), which is built for x86_64 by default during cross-compilation.

This isn't a breaking bug, as WeeWX will detect catch the import error, and figure the package is not installed.

See:

• https://github.com/weewx/weewx/blob/1566a768af0963a43bd1c7b174293c46226a7fb5/src/weewx/engine.py#L852-L858

To reproduce

Steps to reproduce the behavior:

1. Build the WeeWX Docker container for any non-x86 platform using Docker Buildx:

   docker buildx build --platform linux/arm64 -t weewx-arm64 .

2. Run a container from the image.
3. Open a Python interpreter inside the container and attempt to import the ephem module:

   python -c "import ephem"

Expected behavior

The ephem module should import successfully without errors, and the _libastro shared object should be compiled for the target architecture.

Any helpful log output or screenshots

Paste the results here:

>>> import ephem
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/opt/venv/lib/python3.13/site-packages/ephem/__init__.py", line 5, in <module>
    import ephem._libastro as _libastro
ModuleNotFoundError: No module named 'ephem._libastro'

Add any screenshots of the problem here.

---

Proposed Fix

The issue was resolved by modifying the Dockerfile to ensure that the ephem package is compiled from source during the build process. The following changes were made:

1. Added build tools and dependencies to the build-stage:

   RUN apt-get update && apt-get install -y build-essential python3-dev libffi-dev gcc

2. Forced the ephem package to compile from source using pip:

   RUN pip install --no-cache --no-binary :all: ephem

These changes ensure that the _libastro shared object is built correctly for the target architectures, resolving the import issue.