prototype of so-only wheel and cffi interface

.github/workflows/build-wheel-linux.yml

@@ -0,0 +1,46 @@
+# (C) Copyright 2024- ECMWF.
+#
+# This software is licensed under the terms of the Apache Licence Version 2.0
+# which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
+# In applying this licence, ECMWF does not waive the privileges and immunities
+# granted to it by virtue of its status as an intergovernmental organisation
+# nor does it submit to any jurisdiction.
+
+
+name: Build Python Wheel for Linux
+
+on:
+  # Trigger the workflow manually
+  workflow_dispatch: ~
+
+  # Allow to be called from another workflow
+  workflow_call: ~
+
+  # TODO automation trigger
+
+jobs:
+  build:
+    name: Build manylinux_2_28
+    runs-on: [self-hosted, Linux, platform-builder-Rocky-8.6]
+    # TODO which manylinux do we want to build for? 2014? 2_28? 2_34? Matrix?
+    container:
+      image: eccr.ecmwf.int/wheelmaker/2_28:latest
+      credentials:
+        username: ${{ secrets.ECMWF_DOCKER_REGISTRY_USERNAME }}
+        password: ${{ secrets.ECMWF_DOCKER_REGISTRY_ACCESS_TOKEN }}
+    steps:
+        # TODO convert this to be matrix-friendly. Note it's a bit tricky since
+        # we'd ideally not reexecute the compile step multiple times, but it
+        # (non-essentially) depends on a matrix-based step
+        # NOTE we dont use action checkout because it doesnt cleanup after itself correctly
+      - run: git clone --depth=1 --branch="${GITHUB_REF#refs/heads/}" https://github.com/$GITHUB_REPOSITORY /proj
+      - run: cd /proj && /buildscripts/prepare_deps.sh ./python_wrapper/buildconfig 3.11
+      - run: cd /proj && /buildscripts/compile.sh ./python_wrapper/buildconfig
+      - run: cd /proj && PYTHONPATH=/buildscripts /buildscripts/wheel-linux.sh ./python_wrapper/buildconfig 3.11
+      - run: cd /proj && /buildscripts/test-wheel.sh ./python_wrapper/buildconfig 3.11 /tmp/build/wheel/*whl
+      - run: cd /proj && /buildscripts/upload-pypi.sh /tmp/build/wheel/*whl
+        env:
+          TWINE_USERNAME: __token__
+          TWINE_PASSWORD: ${{ secrets.PYPI_API_TOKEN }}
+        # NOTE temporary thing until all the mess gets cleared
+      - run: rm -rf ./* ./.git ./.github

.gitignore

@@ -9,3 +9,7 @@ doc/latex
 .*un~
 *.ccls-cache
 share
+__pycache__/
+*.pyc
+*.egg-info/
+

python_interface/README.md

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+This is just a placeholder for proper python interface of metkit -- for now we just showcase `findlibs`-based finding of `.so`, and loading via cffi.
+
+To demonstrate functionality, install `eckit` and `metkit` binary wheels in your venv, and then you can `pip install -e . && python -c 'import metkit; metkit.version()`.
+
+To be done:
+1. proper cffi setup
+2. wheel building (note this is **not** a binary wheel! That happens in `../python_wrapper`, and contains no python code)

python_interface/pyproject.toml

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+[build-system]
+requires = ["setuptools >= 61.0"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "pymetkit"
+version = "0.0.0"
+dependencies = ["cffi", "findlibs"]

python_interface/src/pymetkit/__init__.py

@@ -0,0 +1,18 @@
+import cffi
+import findlibs
+
+_lib = None
+
+# TODO expose the full functionality
+
+def _get_lib():
+    global _lib
+    if _lib is None:
+        ffi = cffi.FFI()
+        ffi.cdef("unsigned int metkit_version_int();")
+        loc = findlibs.find("metkit", "metkitlibs")
+        _lib = ffi.dlopen(loc)
+    return _lib
+
+def metkit_version_int() -> int:
+    return _get_lib().metkit_version_int()

python_wrapper/buildconfig

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+# (C) Copyright 2024- ECMWF.
+#
+# This software is licensed under the terms of the Apache Licence Version 2.0
+# which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
+# In applying this licence, ECMWF does not waive the privileges and immunities
+# granted to it by virtue of its status as an intergovernmental organisation
+# nor does it submit to any jurisdiction.
+
+# to be source'd by wheelmaker's compile.sh *and* wheel-linux.sh
+# NOTE replace the whole thing with pyproject.toml? Less powerful, and quaint to use for sourcing ecbuild invocation
+# TODO we duplicate information -- pyproject.toml's `name` and `packages` are derivable from $NAME and must stay consistent
+
+NAME="metkit"
+CMAKE_PARAMS="-DECKIT_PATH=/tmp/prereqs/eckitlib"
+PYPROJECT_DIR="python_wrapper"
+DEPENDENCIES='["eckitlib"]'

python_wrapper/setup.cfg

@@ -0,0 +1,5 @@
+[metadata]
+description = "metkitlib"
+long_description = file: README.md
+long_description_content_type = text/markdown
+author = file: AUTHORS

python_wrapper/setup.py

@@ -0,0 +1,2 @@
+from setup_utils import plain_setup
+plain_setup()