ENH: Add support for targeting iOS

Author: freakboy3742

docs/reference/environment-variables.rst

@@ -61,6 +61,22 @@ Environment variables used by meson-python
 .. _cross build definition file: https://mesonbuild.com/Cross-compilation.html
 .. _cibuildwheel: https://cibuildwheel.readthedocs.io/en/stable/
 
+.. envvar:: IPHONEOS_DEPLOYMENT_TARGET
+
+   This environment variable is used to specify the target iOS platform version
+   to the Xcode development tools.  If this environment variable is set,
+   ``meson-python`` will use the specified iOS version for the Python wheel
+   platform tag, instead than the iOS platform default of 13.0.
+
+   This variable must be set to a major/minor version (e.g., ``13.0`` or
+   ``15.4``).
+
+   Note that ``IPHONEOS_DEPLOYMENT_TARGET`` is the only supported mechanism
+   for specifying the target iOS version. Although the iOS toolchain supports
+   the use of ``-mios-version-min`` compile and link flags to set the target iOS
+   version, ``meson-python`` will not set the Python wheel platform tag
+   correctly unless ``IPHONEOS_DEPLOYMENT_TARGET`` is set.
+
 .. envvar:: FORCE_COLOR
 
    Setting this environment variable to any value forces the use of ANSI
@@ -69,11 +85,10 @@ Environment variables used by meson-python
 
 .. envvar:: MACOSX_DEPLOYMENT_TARGET
 
-   This environment variables is used of specifying the target macOS platform
-   major version to the Xcode development tools.  If this environment variable
-   is set, ``meson-python`` will use the specified macOS version for the
-   Python wheel platform tag instead than the macOS version of the build
-   machine.
+   This environment variable is used to specify the target macOS platform major
+   version to the Xcode development tools.  If this environment variable is set,
+   ``meson-python`` will use the specified macOS version for the Python wheel
+   platform tag instead than the macOS version of the build machine.
 
    This variable must be set to macOS major versions only: ``10.9`` to
    ``10.15``, ``11``, ``12``, ``13``, ...
@@ -84,10 +99,11 @@ Environment variables used by meson-python
    are currently designed to specify compatibility only with major version
    number granularity.
 
-   Another way of specifying the target macOS platform is to use the
-   ``-mmacosx-version-min`` compile and link flags.  However, it is not
-   possible for ``meson-python`` to detect this, and it will not set the
-   Python wheel platform tag accordingly.
+   Note that ``MACOSX_DEPLOYMENT_TARGET`` is the only supported mechanism for
+   specifying the target macOS version. Although the macOS toolchain supports
+   the use of ``-mmacosx-version-min`` compile and link flags to set the target
+   macOS version, ``meson-python`` will not set the Python wheel platform tag
+   correctly unless ``MACOSX_DEPLOYMENT_TARGET`` is set.
 
 .. envvar:: MESON
 

docs/reference/meson-compatibility.rst

@@ -52,6 +52,10 @@ versions.
    populate the package license and license files from the ones
    declared via the ``project()`` call in ``meson.build``.
 
+.. option:: 1.9.0
+
+   Meson 1.9.0 or later is required to support building for iOS.
+
 Build front-ends by default build packages in an isolated Python
 environment where build dependencies are installed. Most often, unless
 a package or its build dependencies declare explicitly a version

mesonpy/__init__.py

@@ -719,6 +719,30 @@ def __init__(
                     ''')
                     self._meson_cross_file.write_text(cross_file_data, encoding='utf-8')
                     self._meson_args['setup'].extend(('--cross-file', os.fspath(self._meson_cross_file)))
+        elif sysconfig.get_platform().startswith('ios-'):
+            ios_ver = platform.ios_ver()  # type: ignore[attr-defined]
+
+            arch = platform.machine()
+            family = 'aarch64' if arch == 'arm64' else arch
+            subsystem = 'ios-simulator' if ios_ver.is_simulator else 'ios'
+
+            cross_file_data = textwrap.dedent(f'''
+                [binaries]
+                c = '{arch}-apple-{subsystem}-clang'
+                cpp = '{arch}-apple-{subsystem}-clang++'
+                objc = '{arch}-apple-{subsystem}-clang'
+                objcpp = '{arch}-apple-{subsystem}-clang++'
+                ar = '{arch}-apple-{subsystem}-ar'
+
+                [host_machine]
+                system = 'ios'
+                subsystem = {subsystem!r}
+                cpu = {arch!r}
+                cpu_family = {family!r}
+                endian = 'little'
+            ''')
+            self._meson_cross_file.write_text(cross_file_data, encoding='utf-8')
+            self._meson_args['setup'].extend(('--cross-file', os.fspath(self._meson_cross_file)))
 
         # write the native file
         native_file_data = textwrap.dedent(f'''

mesonpy/_tags.py

@@ -160,10 +160,28 @@ def _get_macosx_platform_tag() -> str:
     return f'macosx_{major}_{minor}_{arch}'
 
 
+def _get_ios_platform_tag() -> str:
+    # Override the iOS version if one is provided via the
+    # IPHONEOS_DEPLOYMENT_TARGET environment variable.
+    try:
+        version = tuple(map(int, os.environ.get('IPHONEOS_DEPLOYMENT_TARGET', '').split('.')))[:2]
+    except ValueError:
+        version = tuple(map(int, platform.ios_ver().release.split('.')))[:2]  # type: ignore[attr-defined]
+
+    # Although _multiarch is an internal implementation detail, it's a core part
+    # of how CPython is implemented on iOS; this attribute is also relied upon
+    # by `packaging` as part of tag determiniation.
+    multiarch = sys.implementation._multiarch.replace('-', '_')
+
+    return f"ios_{version[0]}_{version[1]}_{multiarch}"
+
+
 def get_platform_tag() -> str:
     platform = sysconfig.get_platform()
     if platform.startswith('macosx'):
         return _get_macosx_platform_tag()
+    if platform.startswith('ios'):
+        return _get_ios_platform_tag()
     if _32_BIT_INTERPRETER:
         # 32-bit Python running on a 64-bit kernel.
         if platform == 'linux-x86_64':

pyproject.toml

@@ -8,7 +8,8 @@ backend-path = ['.']
 requires = [
   'meson >= 0.64.0; python_version < "3.12"',
   'meson >= 1.2.3; python_version >= "3.12"',
-  'packaging >= 23.2',
+  'packaging >= 23.2; sys_platform != "ios"',
+  'packaging >= 24.2; sys_platform == "ios"',
   'pyproject-metadata >= 0.9.0',
   'tomli >= 1.0.0; python_version < "3.11"',
 ]
@@ -37,7 +38,8 @@ classifiers = [
 dependencies = [
   'meson >= 0.64.0; python_version < "3.12"',
   'meson >= 1.2.3; python_version >= "3.12"',
-  'packaging >= 23.2',
+  'packaging >= 23.2; sys_platform != "ios"',
+  'packaging >= 24.2; sys_platform == "ios"',
   'pyproject-metadata >= 0.9.0',
   'tomli >= 1.0.0; python_version < "3.11"',
 ]

tests/test_project.py

@@ -4,10 +4,14 @@
 
 import ast
 import os
+import platform
 import shutil
 import sys
+import sysconfig
 import textwrap
 
+from unittest.mock import Mock
+
 
 if sys.version_info < (3, 11):
     import tomli as tomllib
@@ -373,3 +377,37 @@ def test_archflags_envvar_parsing_invalid(package_purelib_and_platlib, monkeypat
     finally:
         # revert environment variable setting done by the in-process build
         os.environ.pop('_PYTHON_HOST_PLATFORM', None)
+
+
+@pytest.mark.skipif(sys.version_info < (3, 13), reason='requires Python 3.13 or higher')
+@pytest.mark.parametrize('multiarch', [
+    'arm64-iphoneos',
+    'arm64-iphonesimulator',
+    'x86_64-iphonesimulator',
+])
+def test_ios_project(package_simple, monkeypatch, multiarch, tmp_path):
+    arch, abi = multiarch.split('-')
+    subsystem = 'ios-simulator' if abi == 'iphonesimulator' else 'ios'
+
+    # Mock being on iOS
+    monkeypatch.setattr(sys, 'platform', 'ios')
+    monkeypatch.setattr(platform, 'machine', Mock(return_value=arch))
+    monkeypatch.setattr(sysconfig, 'get_platform', Mock(return_value=f"ios-13.0-{multiarch}"))
+    ios_ver = platform.IOSVersionInfo('iOS', '13.0', 'iPhone', multiarch.endswith('simulator'))
+    monkeypatch.setattr(platform, 'ios_ver', Mock(return_value=ios_ver))
+
+    # Create an iOS project.
+    project = mesonpy.Project(source_dir=package_simple, build_dir=tmp_path)
+
+    # Meson configuration points at the cross file
+    assert project._meson_args['setup'] == ['--cross-file', os.fspath(tmp_path / 'meson-python-cross-file.ini')]
+
+    # Meson config files exist, and have some relevant keys
+    assert (tmp_path / 'meson-python-native-file.ini').exists()
+    assert (tmp_path / 'meson-python-cross-file.ini').exists()
+
+    cross_config = (tmp_path / 'meson-python-cross-file.ini').read_text()
+
+    assert "\nsystem = 'ios'\n" in cross_config
+    assert f"\nc = '{arch}-apple-{subsystem}-clang'\n" in cross_config
+    assert f"\nsubsystem = '{subsystem}'\n" in cross_config

tests/test_tags.py

@@ -10,6 +10,7 @@
 import sysconfig
 
 from collections import defaultdict
+from unittest.mock import Mock
 
 import packaging.tags
 import pytest
@@ -74,6 +75,25 @@ def test_python_host_platform(monkeypatch):
     assert mesonpy._tags.get_platform_tag().endswith('x86_64')
 
 
+@pytest.mark.skipif(sys.version_info < (3, 13), reason='requires Python 3.13 or higher')
+@pytest.mark.skipif(sys.platform != 'darwin', reason='macOS specific test')
+def test_ios_platform_tag(monkeypatch):
+    # Mock being on iOS
+    monkeypatch.setattr(sys.implementation, '_multiarch', 'arm64-iphoneos')
+    monkeypatch.setattr(sysconfig, 'get_platform', Mock(return_value='ios-13.0-arm64-iphoneos'))
+    ios_ver = platform.IOSVersionInfo('iOS', '13.0', 'iPhone', False)
+    monkeypatch.setattr(platform, 'ios_ver', Mock(return_value=ios_ver))
+
+    # Check the default value
+    assert next(packaging.tags.ios_platforms((13, 0))) == mesonpy._tags.get_platform_tag()
+
+    # Check the value when IPHONEOS_DEPLOYMENT_TARGET is set.
+    for major in range(13, 20):
+        for minor in range(3):
+            monkeypatch.setenv('IPHONEOS_DEPLOYMENT_TARGET', f'{major}.{minor}')
+            assert next(packaging.tags.ios_platforms((major, minor))) == mesonpy._tags.get_platform_tag()
+
+
 def wheel_builder_test_factory(content, pure=True, limited_api=False):
     manifest = defaultdict(list)
     manifest.update({key: [(pathlib.Path(x), os.path.join('build', x)) for x in value] for key, value in content.items()})