ENH: fix support for Python limited API / stable ABI wheels

Meson gained support for building Python extension modules targeting
the Python limited API, therefore it is time for meson-python to
properly support tagging the build wheels as targeting the stable ABI.

Unfortunately there isn't a reliable and cross-platform way to detect
when extension modules are build for the limited API. Therefore, we
need to add an explicit "limited-api" configuration option in the
[tool.meson-python] section in pyproject.toml.

mesonpy/__init__.py

@@ -128,9 +128,8 @@ def _init_colors() -> Dict[str, str]:
 
 
 _SUFFIXES = importlib.machinery.all_suffixes()
-_EXTENSION_SUFFIXES = importlib.machinery.EXTENSION_SUFFIXES
-_EXTENSION_SUFFIX_REGEX = re.compile(r'^\.(?:(?P<abi>[^.]+)\.)?(?:so|pyd|dll)$')
-assert all(re.match(_EXTENSION_SUFFIX_REGEX, x) for x in _EXTENSION_SUFFIXES)
+_EXTENSION_SUFFIX_REGEX = re.compile(r'^[^.]+\.(?:(?P<abi>[^.]+)\.)?(?:so|pyd|dll)$')
+assert all(re.match(_EXTENSION_SUFFIX_REGEX, f'foo{x}') for x in importlib.machinery.EXTENSION_SUFFIXES)
 
 
 # Map Meson installation path placeholders to wheel installation paths.
@@ -344,34 +343,20 @@ def entrypoints_txt(self) -> bytes:
 
     @cached_property
     def _stable_abi(self) -> Optional[str]:
-        """Determine stabe ABI compatibility.
-
-        Examine all files installed in {platlib} that look like
-        extension modules (extension .pyd on Windows, .dll on Cygwin,
-        and .so on other platforms) and, if they all share the same
-        PEP 3149 filename stable ABI tag, return it.
-
-        Other files are ignored.
-
-        """
-        soext = sorted(_EXTENSION_SUFFIXES, key=len)[0]
-        abis = []
-
-        for path, _ in self._wheel_files['platlib']:
-            # NOTE: When searching for shared objects files, we assume the host
-            # and build machines have the same soext, even though that we might
-            # be cross compiling.
-            if path.suffix == soext:
-                match = re.match(r'^[^.]+(.*)$', path.name)
-                assert match is not None
-                suffix = match.group(1)
-                match = _EXTENSION_SUFFIX_REGEX.match(suffix)
+        if self._project._limited_api:
+            # Verify stabe ABI compatibility: examine files installed
+            # in {platlib} that look like extension modules, and raise
+            # an exception if any of them has a Python version
+            # specific extension filename suffix ABI tag.
+            for path, _ in self._wheel_files['platlib']:
+                match = _EXTENSION_SUFFIX_REGEX.match(path.name)
                 if match:
-                    abis.append(match.group('abi'))
-
-        stable = [x for x in abis if x and re.match(r'abi\d+', x)]
-        if len(stable) > 0 and len(stable) == len(abis) and all(x == stable[0] for x in stable[1:]):
-            return stable[0]
+                    abi = match.group('abi')
+                    if abi is not None and abi != 'abi3':
+                        raise BuildError(
+                            f'The package declares compatibility with Python limited API but extension '
+                            f'module {os.fspath(path)!r} is tagged for a specific Python version.')
+            return 'abi3'
         return None
 
     @property
@@ -576,10 +561,16 @@ def _strings(value: Any, name: str) -> List[str]:
             raise ConfigError(f'Configuration entry "{name}" must be a list of strings')
         return value
 
+    def _bool(value: Any, name: str) -> bool:
+        if not isinstance(value, bool):
+            raise ConfigError(f'Configuration entry "{name}" must be a boolean')
+        return value
+
     scheme = _table({
+        'limited-api': _bool,
         'args': _table({
             name: _strings for name in _MESON_ARGS_KEYS
-        })
+        }),
     })
 
     table = pyproject.get('tool', {}).get('meson-python', {})
@@ -648,6 +639,7 @@ def __init__(
         self._meson_native_file = self._build_dir / 'meson-python-native-file.ini'
         self._meson_cross_file = self._build_dir / 'meson-python-cross-file.ini'
         self._meson_args: MesonArgs = collections.defaultdict(list)
+        self._limited_api = False
 
         _check_meson_version()
 
@@ -693,6 +685,7 @@ def __init__(
         pyproject_config = _validate_pyproject_config(pyproject)
         for key, value in pyproject_config.get('args', {}).items():
             self._meson_args[key].extend(value)
+        self._limited_api = pyproject_config.get('limited-api', False)
 
         # meson arguments from the command line take precedence over
         # arguments from the configuration file thus are added later

tests/test_tags.py

@@ -25,7 +25,6 @@
 PLATFORM = adjust_packaging_platform_tag(tag.platform)
 
 SUFFIX = sysconfig.get_config_var('EXT_SUFFIX')
-ABI3SUFFIX = next((x for x in mesonpy._EXTENSION_SUFFIXES if '.abi3.' in x), None)
 
 
 def test_wheel_tag():
@@ -76,19 +75,3 @@ def test_tag_platlib_wheel(monkeypatch):
         'platlib': [f'extension{SUFFIX}'],
     })
     assert str(builder.tag) == f'{INTERPRETER}-{ABI}-{PLATFORM}'
-
-
-@pytest.mark.skipif(not ABI3SUFFIX, reason='Stable ABI not supported by Python interpreter')
-def test_tag_stable_abi(monkeypatch):
-    builder = wheel_builder_test_factory(monkeypatch, {
-        'platlib': [f'extension{ABI3SUFFIX}'],
-    })
-    assert str(builder.tag) == f'{INTERPRETER}-abi3-{PLATFORM}'
-
-
-@pytest.mark.skipif(not ABI3SUFFIX, reason='Stable ABI not supported by Python interpreter')
-def test_tag_mixed_abi(monkeypatch):
-    builder = wheel_builder_test_factory(monkeypatch, {
-        'platlib': [f'extension{ABI3SUFFIX}', f'another{SUFFIX}'],
-    })
-    assert str(builder.tag) == f'{INTERPRETER}-{ABI}-{PLATFORM}'

tests/test_wheel.py

@@ -276,3 +276,21 @@ def test_skip_subprojects(package_subproject, tmp_path, arg):
         'subproject-1.0.0.dist-info/WHEEL',
         'subproject.py',
     }
+
+
+# Requires Meson 1.3.0, see https://github.com/mesonbuild/meson/pull/11745.
+@pytest.mark.skipif(MESON_VERSION < (1, 2, 99), reason='Meson version too old')
+def test_limited_api(wheel_limited_api):
+    artifact = wheel.wheelfile.WheelFile(wheel_limited_api)
+    name = artifact.parsed_filename
+    assert name.group('pyver') == INTERPRETER
+    assert name.group('abi') == 'abi3'
+    assert name.group('plat') == PLATFORM
+
+
+# Requires Meson 1.3.0, see https://github.com/mesonbuild/meson/pull/11745.
+@pytest.mark.skipif(MESON_VERSION < (1, 2, 99), reason='Meson version too old')
+def test_limited_api_bad(package_limited_api, tmp_path):
+    with pytest.raises(mesonpy.BuildError, match='The package declares compatibility with Python limited API but '):
+        with mesonpy.Project.with_temp_working_dir(meson_args={'setup': ['-Dextra=true']}) as project:
+            project.wheel(tmp_path)