Add an integration test and debug issues with the meson backend (#2718)

* Add an integration test with the meson backend

* Modify script to allow testing of the GHA action on a PR

* Try adding cython to languages in meson config

* Revert "Try adding cython to languages in meson config"

This reverts commit 50378a1c7e38665492ad0c683b178e4d96928e1e.

* Pass --vsenv to meson on windows

As seen here https://github.com/matplotlib/matplotlib/blob/9957c394bd01deb7a9bd9cb27804f447a52dc522/.github/workflows/cibuildwheel.yml#L114

* Disable win32 builds for the meson test

* Move the windows-specific config into the test project definition

This is so it can be tested with bin/run_example_ci_configs.py

* Add some docs to the FAQ about meson on windows

* Update bin/run_example_ci_configs.py

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>

---------

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>

bin/run_example_ci_configs.py

@@ -16,6 +16,8 @@ import click
 
 DIR = Path(__file__).parent.parent.resolve()
 
+BuildBackend = typing.Literal["setuptools", "meson"]
+
 
 def shell(cmd: str, *, check: bool, **kwargs: object) -> subprocess.CompletedProcess[str]:
     return subprocess.run([cmd], shell=True, check=check, **kwargs)  # type: ignore[call-overload, no-any-return]
@@ -27,11 +29,17 @@ def git_repo_has_changes() -> bool:
     return unstaged_changes or staged_changes
 
 
-def generate_basic_project(path: Path) -> None:
+def generate_project(path: Path, build_backend: BuildBackend) -> None:
     sys.path.insert(0, "")
-    from test.test_projects.c import new_c_project  # noqa: PLC0415
+    match build_backend:
+        case "meson":
+            from test.test_projects.meson import new_meson_project as new_project  # noqa: PLC0415
+        case "setuptools":
+            from test.test_projects.setuptools import new_c_project as new_project  # noqa: PLC0415
+        case _:
+            typing.assert_never(build_backend)
 
-    project = new_c_project()
+    project = new_project()
     project.generate(path)
 
 
@@ -126,8 +134,9 @@ def ci_service_for_config_file(config_file: Path) -> CIService:
 
 @click.command()
 @click.argument("config_files", nargs=-1, type=click.Path())
+@click.option("--build-backend", type=click.Choice(["setuptools", "meson"]), default="setuptools")
 def run_example_ci_configs(
-    config_files: list[str],
+    config_files: list[str], build_backend: BuildBackend = "setuptools"
 ) -> None:
     """
     Test the example configs. If no files are specified, will test
@@ -166,7 +175,7 @@ def run_example_ci_configs(
         shell(f"git checkout --orphan {branch_name}", check=True)
 
         example_project = Path("example_root")
-        generate_basic_project(example_project)
+        generate_project(example_project, build_backend=build_backend)
 
         for config_file in config_file_paths:
             service = ci_service_for_config_file(config_file)

docs/faq.md

@@ -99,6 +99,21 @@ Second, there might be platforms you want to ship for that NumPy (or some other
 
 (Note the `*_ONLY_BINARY` variable also supports `":all:"`, and you don't need both that and `*_PREFER_BINARY`, you can use either one, depending on if you want a missing wheel to be a failure or an attempt to build in CI.)
 
+### Building with Meson-Python on Windows
+
+Meson generally works well with cibuildwheel, but there are a few things to be aware of:
+
+-   On GitHub Actions, the compiler that's chosen by default on Windows is often the MinGW compiler, rather than the MSVC toolchain that Python was compiled with.
+
+    The simplest fix for this is to configure cibuildwheel to pass the `--vsenv` flag to meson, like this:
+
+    ```toml
+    [tool.cibuildwheel.windows]
+    config-settings = { "setup-args" = "--vsenv" }
+    ```
+
+-   If you need to build 32-bit Windows wheels, you need to activate a 32-bit compiler toolchain before starting cibuildwheel. Many users use [ilammy/msvc-dev-cmd](https://github.com/ilammy/msvc-dev-cmd) for this purpose.
+
 ### Automatic updates using Dependabot {: #automatic-updates}
 
 Selecting a moving target (like the latest release) is generally a bad idea in CI. If something breaks, you can't tell whether it was your code or an upstream update that caused the breakage, and in a worst-case scenario, it could occur during a release.

test/test_build_frontend_args.py

@@ -2,8 +2,7 @@ import subprocess
 
 import pytest
 
-from . import utils
+from . import test_projects, utils
-from .test_projects.c import new_c_project
 
 
 @pytest.mark.parametrize(
@@ -14,7 +13,7 @@ from .test_projects.c import new_c_project
     ],
 )
 def test_build_frontend_args(tmp_path, capfd, frontend_name):
-    project = new_c_project()
+    project = test_projects.new_c_project()
     project_dir = tmp_path / "project"
     project.generate(project_dir)
 

test/test_meson_python.py

@@ -0,0 +1,29 @@
+import packaging.utils
+
+from . import test_projects, utils
+
+meson_project = test_projects.new_meson_project()
+
+
+def test_meson_python_basic(tmp_path, build_frontend_env):
+    """Test that cibuildwheel can build a project with meson-python backend."""
+    project_dir = tmp_path / "project"
+
+    meson_project.generate(project_dir)
+
+    # build the wheels
+    actual_wheels = utils.cibuildwheel_run(
+        project_dir,
+        add_env=build_frontend_env,
+        single_python=True,
+    )
+
+    # check that the expected wheels are produced
+    # note that the meson test project doesn't support win32.
+    is_windows = utils.get_platform() == "windows"
+    expected_wheels = utils.expected_wheels(
+        "spam", "0.1.0", single_python=True, single_arch=is_windows
+    )
+    actual_wheels_normalized = {packaging.utils.parse_wheel_filename(w) for w in actual_wheels}
+    expected_wheels_normalized = {packaging.utils.parse_wheel_filename(w) for w in expected_wheels}
+    assert actual_wheels_normalized == expected_wheels_normalized

test/test_projects/__init__.py

@@ -1,4 +1,5 @@
 from .base import TestProject
-from .c import new_c_project
+from .meson import new_meson_project
+from .setuptools import new_c_project
 
-__all__ = ("TestProject", "new_c_project")
+__all__ = ("TestProject", "new_c_project", "new_meson_project")

test/test_projects/c.py

@@ -1,7 +1,3 @@
-import jinja2
-
-from .base import TestProject
-
 SPAM_C_TEMPLATE = r"""
 #include <Python.h>
 
@@ -39,70 +35,3 @@ PyMODINIT_FUNC PyInit_spam(void)
     return PyModule_Create(&moduledef);
 }
 """
-
-SETUP_PY_TEMPLATE = r"""
-import os
-import sys
-
-from setuptools import setup, Extension
-
-{{ setup_py_add }}
-
-libraries = []
-# Emscripten fails if you pass -lc...
-# See: https://github.com/emscripten-core/emscripten/issues/16680
-if sys.platform.startswith('linux') and "emscripten" not in os.environ.get("_PYTHON_HOST_PLATFORM", ""):
-    libraries.extend(['m', 'c'])
-
-
-setup(
-    ext_modules=[Extension(
-        'spam',
-        sources=['spam.c'],
-        libraries=libraries,
-        {{ setup_py_extension_args_add | indent(8) }}
-    )],
-    {{ setup_py_setup_args_add | indent(4) }}
-)
-"""
-
-SETUP_CFG_TEMPLATE = r"""
-[metadata]
-name = spam
-version = 0.1.0
-
-{{ setup_cfg_add }}
-"""
-
-
-def new_c_project(
-    *,
-    spam_c_top_level_add: str = "",
-    spam_c_function_add: str = "",
-    setup_py_add: str = "",
-    setup_py_extension_args_add: str = "",
-    setup_py_setup_args_add: str = "",
-    setup_cfg_add: str = "",
-) -> TestProject:
-    project = TestProject()
-
-    project.files.update(
-        {
-            "spam.c": jinja2.Template(SPAM_C_TEMPLATE),
-            "setup.py": jinja2.Template(SETUP_PY_TEMPLATE),
-            "setup.cfg": jinja2.Template(SETUP_CFG_TEMPLATE),
-        }
-    )
-
-    project.template_context.update(
-        {
-            "spam_c_top_level_add": spam_c_top_level_add,
-            "spam_c_function_add": spam_c_function_add,
-            "setup_py_add": setup_py_add,
-            "setup_py_extension_args_add": setup_py_extension_args_add,
-            "setup_py_setup_args_add": setup_py_setup_args_add,
-            "setup_cfg_add": setup_cfg_add,
-        }
-    )
-
-    return project

test/test_projects/meson.py

@@ -0,0 +1,60 @@
+import jinja2
+
+from .base import TestProject
+from .c import SPAM_C_TEMPLATE
+
+PYPROJECT_TOML_TEMPLATE = r"""
+[build-system]
+requires = ["meson-python"]
+build-backend = "mesonpy"
+
+[project]
+name = "spam"
+version = "0.1.0"
+
+[tool.cibuildwheel.windows]
+config-settings = { "setup-args" = "--vsenv" }
+# building win32 wheels on a 64-bit CI machine with meson-python
+# requires a few extra steps outside cibuildwheel. See
+# https://github.com/pypa/cibuildwheel/pull/2718
+archs = ["auto64"]
+"""
+
+MESON_BUILD_TEMPLATE = r"""
+project('spam', 'c',
+  version: '0.1.0',
+  default_options: ['warning_level=2'],
+)
+
+py = import('python').find_installation(pure: false)
+
+py.extension_module('spam',
+  'spam.c',
+  install: true,
+)
+"""
+
+
+def new_meson_project(
+    *,
+    spam_c_top_level_add: str = "",
+    spam_c_function_add: str = "",
+) -> TestProject:
+    project = TestProject()
+
+    project.files.update(
+        {
+            "spam.c": jinja2.Template(SPAM_C_TEMPLATE),
+            "pyproject.toml": jinja2.Template(PYPROJECT_TOML_TEMPLATE),
+            "meson.build": jinja2.Template(MESON_BUILD_TEMPLATE),
+        }
+    )
+
+    project.template_context.update(
+        {
+            "spam_c_top_level_add": spam_c_top_level_add,
+            "spam_c_function_add": spam_c_function_add,
+        }
+    )
+
+    return project

test/test_projects/setuptools.py

@@ -0,0 +1,71 @@
+import jinja2
+
+from .base import TestProject
+from .c import SPAM_C_TEMPLATE
+
+SETUP_PY_TEMPLATE = r"""
+import os
+import sys
+
+from setuptools import setup, Extension
+
+{{ setup_py_add }}
+
+libraries = []
+# Emscripten fails if you pass -lc...
+# See: https://github.com/emscripten-core/emscripten/issues/16680
+if sys.platform.startswith('linux') and "emscripten" not in os.environ.get("_PYTHON_HOST_PLATFORM", ""):
+    libraries.extend(['m', 'c'])
+
+
+setup(
+    ext_modules=[Extension(
+        'spam',
+        sources=['spam.c'],
+        libraries=libraries,
+        {{ setup_py_extension_args_add | indent(8) }}
+    )],
+    {{ setup_py_setup_args_add | indent(4) }}
+)
+"""
+
+SETUP_CFG_TEMPLATE = r"""
+[metadata]
+name = spam
+version = 0.1.0
+
+{{ setup_cfg_add }}
+"""
+
+
+def new_c_project(
+    *,
+    spam_c_top_level_add: str = "",
+    spam_c_function_add: str = "",
+    setup_py_add: str = "",
+    setup_py_extension_args_add: str = "",
+    setup_py_setup_args_add: str = "",
+    setup_cfg_add: str = "",
+) -> TestProject:
+    project = TestProject()
+
+    project.files.update(
+        {
+            "spam.c": jinja2.Template(SPAM_C_TEMPLATE),
+            "setup.py": jinja2.Template(SETUP_PY_TEMPLATE),
+            "setup.cfg": jinja2.Template(SETUP_CFG_TEMPLATE),
+        }
+    )
+
+    project.template_context.update(
+        {
+            "spam_c_top_level_add": spam_c_top_level_add,
+            "spam_c_function_add": spam_c_function_add,
+            "setup_py_add": setup_py_add,
+            "setup_py_extension_args_add": setup_py_extension_args_add,
+            "setup_py_setup_args_add": setup_py_setup_args_add,
+            "setup_cfg_add": setup_cfg_add,
+        }
+    )
+
+    return project