Modernise setup scripts (#484)

* Transfer project metadata to pyproject.toml.

* Cythonize is now implicit thanks to build-system.

* Revert "Cythonize is now implicit thanks to build-system."

This reverts commit 31bd497.

* Commit to existing structure of setup.py.

* Remove unnecessary alias from setup.cfg.

* Attempt fix package discovery.

* Fix test_python_versions.

* Don't override dir.

* Test with Test PyPI.

* Revert "Test with Test PyPI."

This reverts commit 7cdfe95.

* Pre-commit compliance.

* Remove empty setup.cfg.

* Rely on setuptools defaults for license-files.

* Use recommended syntax for optional dependencies.

* Ruff compliance.

* Correct NumPy pin.

cf_units/tests/integration/parse/test_graph.py

@@ -2,6 +2,7 @@
 #
 # This file is part of cf-units and is released under the BSD license.
 # See LICENSE in the root of the repository for full licensing details.
+# ruff: noqa: E402
 import pytest
 
 antlr4 = pytest.importorskip("antlr4")

cf_units/tests/integration/parse/test_parse.py

@@ -2,6 +2,7 @@
 #
 # This file is part of cf-units and is released under the BSD license.
 # See LICENSE in the root of the repository for full licensing details.
+# ruff: noqa: E402
 import pytest
 
 antlr4 = pytest.importorskip("antlr4")

cf_units/tests/test_coding_standards.py

@@ -128,7 +128,6 @@ def test_python_versions():
 
     # Places that are checked:
     pyproject_toml_file = REPO_DIR / "pyproject.toml"
-    setup_cfg_file = REPO_DIR / "setup.cfg"
     tox_file = REPO_DIR / "tox.ini"
     ci_locks_file = workflows_dir / "ci-locks.yml"
     ci_tests_file = workflows_dir / "ci-tests.yml"
@@ -137,17 +136,17 @@ def test_python_versions():
     text_searches: list[tuple[Path, str]] = [
         (
             pyproject_toml_file,
-            f'target-version = "py{supported_strip[0]}"',
-        ),
-        (
-            setup_cfg_file,
             "\n    ".join(
                 [
-                    f"Programming Language :: Python :: {ver}"
+                    f'"Programming Language :: Python :: {ver}",'
                     for ver in supported
                 ]
             ),
         ),
+        (
+            pyproject_toml_file,
+            f'requires-python = ">={supported[0]}"',
+        ),
         (
             tox_file,
             "[testenv:py{" + ",".join(supported_strip) + "}-lock]",

cf_units/tests/test_tex.py

@@ -2,6 +2,7 @@
 #
 # This file is part of cf-units and is released under the BSD license.
 # See LICENSE in the root of the repository for full licensing details.
+# ruff: noqa: E402
 import pytest
 
 antlr4 = pytest.importorskip("antlr4")

pyproject.toml

@@ -5,11 +5,71 @@ requires = [
   "setuptools_scm[toml]>=7.0",
   "wheel",
   "oldest-supported-numpy",
-  "Cython>=3.0"
+  "Cython>=3.0",
 ]
 # Defined by PEP 517
 build-backend = "setuptools.build_meta"
 
+[project]
+name = "cf-units"
+authors = [
+    {name = "cf-units Contributors", email = "[email protected]"}
+]
+classifiers = [
+    "Development Status :: 5 - Production/Stable",
+    "Intended Audience :: Science/Research",
+    "License :: OSI Approved :: BSD License",
+    "Operating System :: OS Independent",
+    "Programming Language :: Python",
+    "Programming Language :: Python :: 3 :: Only",
+    "Programming Language :: Python :: 3.10",
+    "Programming Language :: Python :: 3.11",
+    "Programming Language :: Python :: 3.12",
+    "Programming Language :: Python :: Implementation :: CPython",
+    "Topic :: Scientific/Engineering",
+    "Topic :: Scientific/Engineering :: Atmospheric Science",
+    "Topic :: Scientific/Engineering :: Oceanography",
+]
+dependencies = [
+    "cftime >=1.2",
+    "jinja2",
+    "numpy <2"
+    # udunits2 cannot be installed with pip, and it is expected to be
+    #  installed separately.
+]
+description = "Units of measure as required by the Climate and Forecast (CF) metadata conventions"
+dynamic = [
+    "version",
+]
+keywords = [
+    "units",
+    "cf",
+    "cf-metadata",
+    "netcdf",
+    "science",
+    "earth-science",
+    "oceanography",
+    "meteorology",
+    "climate",
+    "python",
+]
+license.file = "LICENSE"
+readme = "README.md"
+requires-python = ">=3.10"
+
+[project.optional-dependencies]
+all = ["cf-units[latex]", "cf-units[docs]", "cf-units[test]"]
+# To update antlr: see cf_units/_udunits2_parser/README.md"
+latex = ["antlr4-python3-runtime ==4.11.1"]
+docs = ["sphinx"]
+test = ["codecov", "cython", "jinja2", "pip", "pytest", "pytest-cov"]
+
+[project.urls]
+Code = "https://github.com/SciTools/cf-units"
+Discussions = "https://github.com/SciTools/cf-units/discussions"
+Issues = "https://github.com/SciTools/cf-units/issues"
+Documentation = "https://cf-units.readthedocs.io"
+
 [tool.coverage.run]
 branch = true
 plugins = [
@@ -41,6 +101,9 @@ doctest_optionflags = "NORMALIZE_WHITESPACE ELLIPSIS NUMBER"
 minversion = "6.0"
 testpaths = "cf_units"
 
+[tool.setuptools.packages.find]
+include = ["cf_units"]
+
 [tool.setuptools_scm]
 write_to = "cf_units/_version.py"
 local_scheme = "dirty-tag"
@@ -51,7 +114,6 @@ exclude = [
     "cf_units/_udunits2_parser/parser",
 ]
 line-length = 79
-target-version = "py310"
 
 [tool.ruff.lint]
 select = [

setup.py

@@ -1,3 +1,8 @@
+"""Setup routines to enable cf-units' Cython elements.
+
+All other setup configuration is in `pyproject.toml`.
+"""
+
 import sys
 from distutils.sysconfig import get_config_var
 from os import environ
@@ -6,7 +11,8 @@
 
 from setuptools import Command, Extension, setup
 
-# Default to using cython, but use the .c files if it doesn't exist
+# Default to using cython, but use the .c files if it doesn't exist.
+#  Supports the widest possible range of developer setups.
 try:
     from Cython.Build import cythonize
 except ImportError:
@@ -40,27 +46,14 @@ def run(self):
                 path.unlink()
 
 
-def get_include_dirs():
-    include_dirs = []
-    include_dir = environ.get("UDUNITS2_INCDIR")
-    if include_dir is None:
-        include_dir = get_config_var("INCLUDEDIR")
-    if include_dir is not None:
-        include_dirs.append(include_dir)
-    return include_dirs
-
-
-def get_library_dirs():
-    library_dirs = []
-    library_dir = environ.get("UDUNITS2_LIBDIR")
-    if library_dir is None:
-        library_dir = get_config_var("LIBDIR")
-    if library_dir is not None:
-        library_dirs.append(library_dir)
-    return library_dirs
+def get_dirs(env_var: str, config_var: str):
+    """Get a directory from an env variable or a distutils config variable."""
+    result = environ.get(env_var) or get_config_var(config_var)
+    return [result] if result else []
 
 
 def get_package_data():
+    """Find and correctly package the UDUNITS2 XML files for a wheel build."""
     package_data = {}
     # Determine whether we're building a wheel.
     if "bdist_wheel" in sys.argv:
@@ -99,6 +92,7 @@ def get_package_data():
 
 
 def numpy_build_ext(pars):
+    """Make the NumPy headers available for the Cython layer."""
     from setuptools.command.build_ext import build_ext as _build_ext
 
     class build_ext(_build_ext):
@@ -126,12 +120,16 @@ def _set_builtin(name, value):
         sys.argv.remove(FLAG_COVERAGE)
     print('enable: "linetrace" Cython compiler directive')
 
-library_dirs = get_library_dirs()
+include_dirs = get_dirs("UDUNITS2_INCDIR", "INCLUDEDIR")
+library_dirs = get_dirs("UDUNITS2_LIBDIR", "LIBDIR")
 
+# Some of the complexity MUST remain in setup.py due to its dynamic nature. To
+#  reduce confusion, the Extension is 100% defined here, rather than splitting
+#  between setup.py and pyproject.toml `ext-modules`.
 udunits_ext = Extension(
     f"{PACKAGE}._udunits2",
     [str(Path(f"{PACKAGE}") / f"_udunits2.{'pyx' if cythonize else 'c'}")],
-    include_dirs=get_include_dirs(),
+    include_dirs=include_dirs,
     library_dirs=library_dirs,
     libraries=["udunits2"],
     define_macros=DEFINE_MACROS,
@@ -141,6 +139,7 @@ def _set_builtin(name, value):
 )
 
 if cythonize:
+    # https://docs.cython.org/en/latest/src/userguide/source_files_and_compilation.html#distributing-cython-modules
     [udunits_ext] = cythonize(
         udunits_ext,
         compiler_directives=COMPILER_DIRECTIVES,