Optionally build a pure wheel

Add a new --pure-wheel command line option to also build pure Python
wheel. If not selected, build will fail with a wheel that does not
contain platform-specific code once built.
Also add a new CIBW_PURE_WHEEL environment variable for this option.



Reference: #1021
Signed-off-by: Philippe Ombredanne <pombredanne@nexb.com>

cibuildwheel/__main__.py

@@ -107,6 +107,15 @@ def main() -> None:
         help="Enable pre-release Python versions if available.",
     )
 
+    parser.add_argument(
+        "--pure-wheel",
+        action="store_true",
+        help="""
+            Build pure Python wheel. If not selected, build will fail with a
+            wheel that does not contain platform-specific code.
+        """,
+    )
+
     args = parser.parse_args(namespace=CommandLineArguments())
 
     if args.platform != "auto":

cibuildwheel/linux.py

@@ -229,10 +229,11 @@ def build_on_docker(
         docker.call(["rm", "-rf", repaired_wheel_dir])
         docker.call(["mkdir", "-p", repaired_wheel_dir])
 
-        if built_wheel.name.endswith("none-any.whl"):
+        is_pure_python = built_wheel.name.endswith("none-any.whl")
+        if not build_options.globals.pure_wheel and is_pure_python:
             raise NonPlatformWheelError()
 
-        if build_options.repair_command:
+        if not is_pure_python and build_options.repair_command:
             log.step("Repairing wheel...")
             repair_command_prepared = prepare_command(
                 build_options.repair_command, wheel=built_wheel, dest_dir=repaired_wheel_dir

cibuildwheel/macos.py

@@ -366,10 +366,11 @@ def build(options: Options, tmp_path: Path) -> None:
 
             repaired_wheel_dir.mkdir()
 
-            if built_wheel.name.endswith("none-any.whl"):
+            is_pure_python = built_wheel.name.endswith("none-any.whl")
+            if not build_options.globals.pure_wheel and is_pure_python:
                 raise NonPlatformWheelError()
 
-            if build_options.repair_command:
+            if not is_pure_python and build_options.repair_command:
                 log.step("Repairing wheel...")
 
                 if config_is_universal2:

cibuildwheel/options.py

@@ -47,6 +47,7 @@ class CommandLineArguments:
     print_build_identifiers: bool
     allow_empty: bool
     prerelease_pythons: bool
+    pure_wheel: bool = False
 
 
 class GlobalOptions(NamedTuple):
@@ -55,6 +56,7 @@ class GlobalOptions(NamedTuple):
     build_selector: BuildSelector
     test_selector: TestSelector
     architectures: Set[Architecture]
+    pure_wheel: bool
 
 
 class BuildOptions(NamedTuple):
@@ -356,6 +358,8 @@ def package_requires_python_str(self) -> Optional[str]:
     def globals(self) -> GlobalOptions:
         args = self.command_line_arguments
         package_dir = Path(args.package_dir)
+        pure_wheel = args.pure_wheel or strtobool(os.environ.get("CIBW_PURE_WHEEL", "0"))
+
         output_dir = Path(
             args.output_dir
             if args.output_dir is not None
@@ -394,6 +398,7 @@ def globals(self) -> GlobalOptions:
             build_selector=build_selector,
             test_selector=test_selector,
             architectures=architectures,
+            pure_wheel=pure_wheel,
         )
 
     def build_options(self, identifier: Optional[str]) -> BuildOptions:

cibuildwheel/windows.py

@@ -335,10 +335,11 @@ def build(options: Options, tmp_path: Path) -> None:
             # repair the wheel
             repaired_wheel_dir.mkdir()
 
-            if built_wheel.name.endswith("none-any.whl"):
+            is_pure_python = built_wheel.name.endswith("none-any.whl")
+            if not build_options.globals.pure_wheel and is_pure_python:
                 raise NonPlatformWheelError()
 
-            if build_options.repair_command:
+            if not is_pure_python and build_options.repair_command:
                 log.step("Repairing wheel...")
                 repair_command_prepared = prepare_command(
                     build_options.repair_command, wheel=built_wheel, dest_dir=repaired_wheel_dir

test/test_pure_wheel_built.py

@@ -0,0 +1,48 @@
+from test import test_projects
+
+from . import utils
+
+pure_python_project = test_projects.TestProject()
+pure_python_project.files[
+    "setup.py"
+] = """
+from setuptools import Extension, setup
+
+setup(
+    name="spam",
+    py_modules=['spam'],
+    version="0.1.0",
+)
+"""
+
+pure_python_project.files[
+    "spam.py"
+] = """
+def a_function():
+    pass
+"""
+
+
+def test(tmp_path, capfd):
+    # this test checks that if a pure wheel is generated, the build should
+    # pass with the pure wheel option.
+    project_dir = tmp_path / "project"
+    pure_python_project.generate(project_dir)
+
+    env = {
+        "CIBW_PURE_WHEEL": "yes",
+        # this shouldn't depend on the version of python, so build only CPython 3.6
+        "CIBW_BUILD": "cp36-*",
+    }
+
+    actual_wheels = utils.cibuildwheel_run(project_dir, add_env=env)
+    print("produced wheels:", actual_wheels)
+
+    captured = capfd.readouterr()
+    print("out", captured.out)
+    print("err", captured.err)
+    assert "Build failed because a pure Python wheel was generated" not in captured.err
+
+    # check that the expected wheels are produced
+    expected_wheels = ["spam-0.1.0-py3-none-any.whl"]
+    assert set(actual_wheels) == set(expected_wheels)