feat: add support for building iOS wheels. (#2286)

* Add support for building iOS wheels.

* Replace use of system() in test binary module.

* Restored the 'minimal' approach of the minimal examples.

* Split out platform details into standalone pages, and expand iOS platform details.

* More doc corrections.

* Bump support package to include fix for python/cpython#130292

* Ensure iOS tests are all run on the same xdist worker.

* More iOS documentation tweaks.

* Factor out common xcode version test utility.

* Simplify iOS to a single platform with an expanded interpretation of arch.

* I guess I should update the iOS tests as well...

* Additional safety for missing iOS test output.

* Remove DYLD_LIBRARY_PATH from the iOS environment.

* Make test-sources mandatory for iOS builds.

* Updates and clarifications to documentation.

* Clarify what a slice is.

* Normalize use of underscores in platform name.

* Modify auto target to be matching CPU only.

* Use consistent ordering of platforms in examples.

* Use consistent naming in iOS archiectures.

* Placate the linter.

* Miscellaneous cleanups picked up by @joerick's review.

* Correct the list of expected wheels.

* Correct which 'native' we're actually checking.

* Correct the docs links so they're all relative.

* Correct the identification of free threaded builds.

* Use target instead of host to describe the platform we're building for.

* Rework iOS test to remove issue with log completeness.

* Convert errors to FatalError

Co-authored-by: Matthieu Darbois <mayeut@users.noreply.github.com>
Co-authored-by: Joe Rickerby <joerick@mac.com>

* Removed a repeated check for a valid python.

* Update bin/update_pythons.py to update iOS support packages.

* Document that iOS CI is available on other platforms.

* Restore a comment needed for some platforms.

* Small cleanups identified in code review

Co-authored-by: Joe Rickerby <joerick@mac.com>

* Simplify logic to appease linter.

* Modify dependency constraint handling to use new API.

* Cosmetic change to trigger a CI rebuild.

---------

Co-authored-by: Matthieu Darbois <mayeut@users.noreply.github.com>
Co-authored-by: Joe Rickerby <joerick@mac.com>

test/test_emulation.py

@@ -11,8 +11,8 @@ project_with_a_test.files["test/spam_test.py"] = r"""
 import spam
 
 def test_spam():
-    assert spam.system('python -c "exit(0)"') == 0
-    assert spam.system('python -c "exit(1)"') != 0
+    assert spam.filter("spam") == 0
+    assert spam.filter("ham") != 0
 """
 
 

test/test_ios.py

@@ -0,0 +1,95 @@
+from __future__ import annotations
+
+import os
+import platform
+import subprocess
+
+import pytest
+
+from . import test_projects, utils
+
+basic_project = test_projects.new_c_project()
+basic_project.files["tests/test_platform.py"] = f"""
+import platform
+from unittest import TestCase
+
+class TestPlatform(TestCase):
+    def test_platform(self):
+        self.assertEqual(platform.machine(), "{platform.machine()}")
+
+"""
+
+
+# iOS tests shouldn't be run in parallel, because they're dependent on starting
+# a simulator. It's *possible* to start multiple simulators, but not advisable
+# to start as many simulators as there are CPUs on the test machine.
+@pytest.mark.xdist_group(name="ios")
+@pytest.mark.parametrize(
+    "build_config",
+    [
+        # Default to the pip build frontend
+        {"CIBW_PLATFORM": "ios"},
+        # Also check the build frontend
+        {"CIBW_PLATFORM": "ios", "CIBW_BUILD_FRONTEND": "build"},
+    ],
+)
+def test_ios_platforms(tmp_path, build_config):
+    if utils.platform != "macos":
+        pytest.skip("this test can only run on macOS")
+    if utils.get_xcode_version() < (13, 0):
+        pytest.skip("this test only works with Xcode 13.0 or greater")
+
+    project_dir = tmp_path / "project"
+    basic_project.generate(project_dir)
+
+    actual_wheels = utils.cibuildwheel_run(
+        project_dir,
+        add_env={
+            "CIBW_BUILD": "cp313-*",
+            "CIBW_TEST_SOURCES": "tests",
+            "CIBW_TEST_COMMAND": "unittest discover tests test_platform.py",
+            **build_config,
+        },
+    )
+
+    ios_version = os.getenv("IPHONEOS_DEPLOYMENT_TARGET", "13.0").replace(".", "_")
+    platform_machine = platform.machine()
+
+    # Tests are only executed on simulator. The test suite passes if it's
+    # running on the same architecture as the current platform.
+    if platform_machine == "x86_64":
+        expected_wheels = {
+            f"spam-0.1.0-cp313-cp313-ios_{ios_version}_x86_64_iphonesimulator.whl",
+        }
+
+    elif platform_machine == "arm64":
+        expected_wheels = {
+            f"spam-0.1.0-cp313-cp313-ios_{ios_version}_arm64_iphoneos.whl",
+            f"spam-0.1.0-cp313-cp313-ios_{ios_version}_arm64_iphonesimulator.whl",
+        }
+
+    assert set(actual_wheels) == expected_wheels
+
+
+@pytest.mark.xdist_group(name="ios")
+def test_no_test_sources(tmp_path, capfd):
+    if utils.platform != "macos":
+        pytest.skip("this test can only run on macOS")
+    if utils.get_xcode_version() < (13, 0):
+        pytest.skip("this test only works with Xcode 13.0 or greater")
+
+    project_dir = tmp_path / "project"
+    basic_project.generate(project_dir)
+
+    with pytest.raises(subprocess.CalledProcessError):
+        utils.cibuildwheel_run(
+            project_dir,
+            add_env={
+                "CIBW_PLATFORM": "ios",
+                "CIBW_BUILD": "cp313-*",
+                "CIBW_TEST_COMMAND": "tests",
+            },
+        )
+
+    captured = capfd.readouterr()
+    assert "Testing on iOS requires a definition of test-sources." in captured.err

test/test_macos_archs.py

@@ -1,5 +1,4 @@
 import platform
-import subprocess
 
 import pytest
 
@@ -20,24 +19,10 @@ ALL_MACOS_WHEELS = {
 DEPLOYMENT_TARGET_TOO_LOW_WARNING = "Bumping MACOSX_DEPLOYMENT_TARGET"
 
 
-def get_xcode_version() -> tuple[int, int]:
-    output = subprocess.run(
-        ["xcodebuild", "-version"],
-        text=True,
-        check=True,
-        stdout=subprocess.PIPE,
-    ).stdout
-    lines = output.splitlines()
-    _, version_str = lines[0].split()
-
-    version_parts = version_str.split(".")
-    return (int(version_parts[0]), int(version_parts[1]))
-
-
 def test_cross_compiled_build(tmp_path):
     if utils.platform != "macos":
         pytest.skip("this test is only relevant to macos")
-    if get_xcode_version() < (12, 2):
+    if utils.get_xcode_version() < (12, 2):
         pytest.skip("this test only works with Xcode 12.2 or greater")
 
     project_dir = tmp_path / "project"
@@ -71,7 +56,7 @@ def test_cross_compiled_build(tmp_path):
 def test_cross_compiled_test(tmp_path, capfd, build_universal2, test_config):
     if utils.platform != "macos":
         pytest.skip("this test is only relevant to macos")
-    if get_xcode_version() < (12, 2):
+    if utils.get_xcode_version() < (12, 2):
         pytest.skip("this test only works with Xcode 12.2 or greater")
 
     project_dir = tmp_path / "project"
@@ -153,7 +138,7 @@ def test_deployment_target_warning_is_firing(tmp_path, capfd):
 def test_universal2_testing_on_x86_64(tmp_path, capfd, skip_arm64_test):
     if utils.platform != "macos":
         pytest.skip("this test is only relevant to macos")
-    if get_xcode_version() < (12, 2):
+    if utils.get_xcode_version() < (12, 2):
         pytest.skip("this test only works with Xcode 12.2 or greater")
     if platform.machine() != "x86_64":
         pytest.skip("this test only works on x86_64")
@@ -223,7 +208,7 @@ def test_universal2_testing_on_arm64(build_frontend_env, tmp_path, capfd):
 def test_cp38_arm64_testing(tmp_path, capfd, request):
     if utils.platform != "macos":
         pytest.skip("this test is only relevant to macos")
-    if get_xcode_version() < (12, 2):
+    if utils.get_xcode_version() < (12, 2):
         pytest.skip("this test only works with Xcode 12.2 or greater")
     if platform.machine() != "arm64":
         pytest.skip("this test only works on arm64")

test/test_projects/c.py

@@ -8,15 +8,16 @@ SPAM_C_TEMPLATE = r"""
 {{ spam_c_top_level_add }}
 
 static PyObject *
-spam_system(PyObject *self, PyObject *args)
+spam_filter(PyObject *self, PyObject *args)
 {
-    const char *command;
+    const char *content;
     int sts;
 
-    if (!PyArg_ParseTuple(args, "s", &command))
+    if (!PyArg_ParseTuple(args, "s", &content))
         return NULL;
 
-    sts = system(command);
+    // Spam should not be allowed through the filter.
+    sts = strcmp(content, "spam");
 
     {{ spam_c_function_add | indent(4) }}
 
@@ -25,7 +26,7 @@ spam_system(PyObject *self, PyObject *args)
 
 /* Module initialization */
 static PyMethodDef module_methods[] = {
-    {"system", (PyCFunction)spam_system, METH_VARARGS,
+    {"filter", (PyCFunction)spam_filter, METH_VARARGS,
      "Execute a shell command."},
     {NULL}  /* Sentinel */
 };

test/test_testing.py

@@ -44,9 +44,9 @@ def path_contains(parent, child):
 
 
 class TestSpam(TestCase):
-    def test_system(self):
-        self.assertEqual(0, spam.system('python -c "exit(0)"'))
-        self.assertNotEqual(0, spam.system('python -c "exit(1)"'))
+    def test_filter(self):
+        self.assertEqual(0, spam.filter("spam"))
+        self.assertNotEqual(0, spam.filter("ham"))
 
     def test_virtualenv(self):
         # sys.prefix is different from sys.base_prefix when running a virtualenv

test/utils.py

@@ -335,6 +335,21 @@ def get_macos_version() -> tuple[int, int]:
     return tuple(map(int, version_str.split(".")[:2]))  # type: ignore[return-value]
 
 
+def get_xcode_version() -> tuple[int, int]:
+    """Calls `xcodebuild -version` to retrieve the Xcode version as a 2-tuple."""
+    output = subprocess.run(
+        ["xcodebuild", "-version"],
+        text=True,
+        check=True,
+        stdout=subprocess.PIPE,
+    ).stdout
+    lines = output.splitlines()
+    _, version_str = lines[0].split()
+
+    version_parts = version_str.split(".")
+    return (int(version_parts[0]), int(version_parts[1]))
+
+
 def skip_if_pyodide(reason: str) -> Any:
     return pytest.mark.skipif(platform == "pyodide", reason=reason)