prototype of so-only wheel and cffi interface

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

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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.
+
+
+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:
+
+    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: wheelmaker_2_28:0.1
+
+    name: Build manylinux_2_28
+
+    steps:
+      # TODO which project do we build odc wheel from -- this, or some bundle? Or can we obtain the compiled eckit artifact somehow?
+      - run: git clone --branch develop --depth=1 https://github.com/ecmwf/eckit.git /src/eckit
+      - run: /buildscripts/compile.sh ./eckit/python_wrapper/buildconfig
+      - uses: actions/checkout@v2
+      - run: /buildscripts/compile.sh ./metkit/python_wrapper/buildconfig
+
+      ################################################################
+      - run: /buildscripts/wheel-linux.sh ./metkit/python_wrapper/buildconfig 3.11
+      - uses: actions/upload-artifact@v4
+        name: Upload wheel 3.11
+        with:
+          name: wheel-manylinux2_28-3.11
+          path: /build/wheel/*.whl
+
+      # TODO other python versions, once the above is correct.
+      # NOTE if Matrix, then break into (compile & upload) ; (wheel & upload)[matix] steps
+
+  test:
+
+    needs: build
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: ["3.11"] # ["3.8", "3.9", "3.10", "3.11", "3.12"] # TODO enable
+
+    name: Test with ${{ matrix.python-version }}
+    runs-on: [self-hosted, Linux, platform-builder-Rocky-8.6]
+    container: wheelmaker_2_28:0.1
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/download-artifact@v4
+        with:
+          name: wheel-manylinux2_28-${{ matrix.python-version }}
+      - run: /buildscripts/test-wheel.sh ${{ matrix.python-version }}
+
+# TODO enable and test
+#  deploy:
+#
+#    if: ${{ github.ref_type == 'tag' || github.event_name == 'release' }}
+#    needs: [test, build]
+#    strategy:
+#      fail-fast: false
+#      matrix:
+#        python-version: ["3.11"] # ["3.8", "3.9", "3.10", "3.11", "3.12"] # TODO enable
+#
+#    name: Deploy wheel ${{ matrix.python-version }}
+#    runs-on: [self-hosted, Linux, platform-builder-Rocky-8.6]
+#    container: wheelmaker_2_28:0.1
+#    steps:
+#      - run: mkdir artifact-${{ matrix.python-version }}
+#      - uses: actions/checkout@v2
+#      - uses: actions/download-artifact@v4
+#        with:
+#          name: wheel-manylinux2_28-${{ matrix.python-version }}
+#          path: artifact-${{ matrix.python-version }}
+#      - run: |
+#      		/buildsripts/upload-twine.sh ${{ matrix.python-version }}
+#        env:
+#          TWINE_USERNAME: __token__
+#          TWINE_PASSWORD: ${{ secrets.PYPI_API_TOKEN }}

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

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+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
+
+NAME="metkit"
+CMAKE_PARAMS="-DECKIT_PATH=/target/eckit"
+PYPROJECT_DIR="python_wrapper"

python_wrapper/setup.cfg

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+[metadata]
+description = "metkit"
+long_description = file: README.md
+long_description_content_type = text/markdown
+author = file: AUTHORS

python_wrapper/setup.py

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+from setup_utils import plain_setup
+plain_setup()