WHL: build limited-api compliant wheels

.github/workflows/cibuildwheel.yml

@@ -42,29 +42,28 @@ jobs:
 
     - name: Build just oldest and newest on PRs, all on tags
       shell: bash
-      # - Always omit musl 3.8 b/c NumPy does not provide wheels for it
       # - Always omit musllinux_aarch64 because it's slow and niche
       # - On PPs, omit musllinux for speed
-      # - On PRs, run just oldest and newest Python versions (and omit 3.8 aarch64)
+      # - On PRs, run just oldest and newest Python versions (3.13 is the oldest abi3 target)
       run: |
         if [[ "${{ github.event_name }}" == "pull_request" ]]; then
-          CIBW_SKIP="cp38-* cp39-* cp310-* cp311-* cp38-*_aarch64 *musllinux*"
+          CIBW_SKIP="cp3{11,12}-* *musllinux*"
         else
-          CIBW_SKIP="cp38-* *musllinux_aarch64"
+          CIBW_SKIP="*musllinux_aarch64"
         fi
         echo "CIBW_SKIP=$CIBW_SKIP" >> $GITHUB_ENV
         echo "Setting CIBW_SKIP=$CIBW_SKIP"
 
     - name: "Building ${{ matrix.os }} (${{ matrix.arch }}) wheels"
-      uses: pypa/cibuildwheel@v3.1.4
+      uses: pypa/cibuildwheel@v3.2.0
       env:
         CIBW_SKIP: ${{ env.CIBW_SKIP }}
         CIBW_ARCHS: ${{ matrix.arch }}
         CIBW_MANYLINUX_X86_64_IMAGE: manylinux2014
         CIBW_MANYLINUX_AARCH64_IMAGE: manylinux2014
-        # Emulated testing is slow, so trust that the Python 3.12 test is good enough on aarch64
+        # Emulated testing is slow, so trust that the Python 3.14 test is good enough on aarch64
         # (takes about 5 minutes per wheel to build, and 5 minutes to test)
-        CIBW_TEST_SKIP: "cp39-*_aarch64 cp310-*_aarch64 cp311-*_aarch64"
+        CIBW_TEST_SKIP: "cp3{10,11,12,13}-*_aarch64"
         CIBW_TEST_GROUPS: dev
         CIBW_TEST_COMMAND: >
           python -c "import cftime; print(f'cftime v{cftime.__version__}')" &&

.github/workflows/tests_conda.yml

@@ -12,7 +12,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: [ "3.9", "3.10", "3.11", "3.12", "3.13" ]
+        python-version: [ "3.10", "3.11", "3.12", "3.13" ]
         os: [windows-latest, ubuntu-latest, macos-latest]
         platform: [x64, x32]
         experimental: [false]

pyproject.toml

@@ -15,18 +15,17 @@ classifiers = [
     'Operating System :: POSIX :: Linux',
     'Programming Language :: Python',
     'Programming Language :: Python :: 3',
-    'Programming Language :: Python :: 3.8',
-    'Programming Language :: Python :: 3.9',
     'Programming Language :: Python :: 3.10',
     'Programming Language :: Python :: 3.11',
     'Programming Language :: Python :: 3.12',
     'Programming Language :: Python :: 3.13',
+    'Programming Language :: Python :: 3.14',
     'Topic :: Scientific/Engineering',
 ]
 dependencies = [
     "numpy>1.13.3",
 ]
-requires-python = ">=3.8"
+requires-python = ">=3.10"
 
 [dependency-groups]
 dev = [
@@ -44,8 +43,7 @@ dev = [
 requires = [
     "setuptools>=77.0.1",
     "cython>=0.29.20",
-    "oldest-supported-numpy ; python_version < '3.9'",
-    "numpy>=2.0.0,<3 ; python_version >= '3.9'",
+    "numpy>=2.0.0,<3",
 ]
 build-backend = "setuptools.build_meta"
 
@@ -103,3 +101,21 @@ ignore = [
     "test",
     "test/*",
 ]
+
+[tool.cibuildwheel]
+build-verbosity = 1
+skip = [
+    "*musllinux_aarch64*",
+]
+
+# Emulated testing is slow, so trust that the Python 3.14 test is good enough on aarch64
+# (takes about 5 minutes per wheel to build, and 5 minutes to test)
+test-skip = [
+    "cp3{10,11,12,13}-*_aarch64",
+]
+test-groups = "dev"
+test-command = [
+    '''python -c "import cftime; print(f'cftime v{cftime.__version__}')"''',
+    "python -m pytest -vv {package}/test"
+]
+environment = {CFTIME_LIMITED_API="1"}

setup.py

@@ -1,5 +1,6 @@
 import os
 import sys
+import sysconfig
 import numpy
 
 from Cython.Build import cythonize
@@ -29,6 +30,21 @@
 CFTIME_DIR = os.path.join(SRCDIR, NAME)
 CYTHON_FNAME = os.path.join(CFTIME_DIR, '_{}.pyx'.format(NAME))
 
+USE_PY_LIMITED_API = (
+    # require opt-in (builds are specialized by default)
+    os.getenv('CFTIME_LIMITED_API', '0') == '1'
+    # Cython + numpy + limited API de facto requires Python >=3.13
+    and sys.version_info >= (3, 13)
+    # as of Python 3.14t, free-threaded builds don't support the limited API
+    and not sysconfig.get_config_var("Py_GIL_DISABLED")
+)
+ABI3_TARGET_VERSION = "".join(str(_) for _ in sys.version_info[:2])
+ABI3_TARGET_HEX = hex(sys.hexversion & 0xFFFF00F0)
+
+if USE_PY_LIMITED_API:
+    SETUP_OPTIONS = {"bdist_wheel": {"py_limited_api": f"cp{ABI3_TARGET_VERSION}"}}
+else:
+    SETUP_OPTIONS = {}
 
 class CleanCython(Command):
     description = 'Purge artifacts built by Cython'
@@ -60,6 +76,8 @@ def run(self):
     }
     DEFINE_MACROS += [('CYTHON_TRACE', '1'),
                      ('CYTHON_TRACE_NOGIL', '1')]
+    if USE_PY_LIMITED_API:
+        DEFINE_MACROS.append(("Py_LIMITED_API", ABI3_TARGET_HEX))
     if FLAG_COVERAGE in sys.argv:
         sys.argv.remove(FLAG_COVERAGE)
     print('enable: "linetrace" Cython compiler directive')
@@ -71,7 +89,8 @@ def run(self):
     extension = Extension('{}._{}'.format(NAME, NAME),
                           sources=[os.path.relpath(CYTHON_FNAME, BASEDIR)],
                           define_macros=DEFINE_MACROS,
-                          include_dirs=[numpy.get_include(),])
+                          include_dirs=[numpy.get_include()],
+                          py_limited_api=USE_PY_LIMITED_API)
 
     ext_modules = cythonize(
         extension,
@@ -82,4 +101,5 @@ def run(self):
 setup(
     cmdclass={'clean_cython': CleanCython},
     ext_modules=ext_modules,
+    options=SETUP_OPTIONS,
 )