Bump version: v2.0.0a4

* feat: support pypa build

fix: update `cibuildwheel.linux.troubleshoot` to know about build

Workaround issue with PyPy venv module by installing build[virtualenv]

fix: test_dependency_constraints_file when using build

fix: test/test_pep518.py

fix: use `strtobool` to parse `CIBW_PYPA_BUILD`

fix: update `cibuildwheel.linux.troubleshoot` to know about `python -m pip wheel`

test: use `build_mode` in `test/test_dependency_versions.py` tests

* refactor: use build-backend instead

* Apply suggestions from code review

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

* refactor: use literal types for build_frontend

* refactor(tests): build_mode -> build_frontend_env

* Update test/test_before_build.py

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

.github/workflows/update-dependencies.yml

@@ -17,6 +17,8 @@ jobs:
       run: nox --force-color -s update_constraints
     - name: "Run update: python configs"
       run: nox --force-color -s update_pins
+    - name: "Run update: docs user projects"
+      run: nox --force-color -s update_proj
 
     # we use this step to grab a Github App auth token, so that PRs generated by this workflow
     # run the GHA tests.

README.md

@@ -85,7 +85,7 @@ jobs:
       - uses: actions/setup-python@v2
 
       - name: Install cibuildwheel
-        run: python -m pip install cibuildwheel==2.0.0a3
+        run: python -m pip install cibuildwheel==2.0.0a4
 
       - name: Build wheels
         run: python -m cibuildwheel --output-dir wheelhouse

cibuildwheel/__init__.py

@@ -1 +1 @@
-__version__ = "2.0.0a3"
+__version__ = "2.0.0a4"

cibuildwheel/__main__.py

@@ -20,6 +20,7 @@ from cibuildwheel.options import ConfigOptions
 from cibuildwheel.projectfiles import get_requires_python_str
 from cibuildwheel.typing import PLATFORMS, PlatformName, assert_never
 from cibuildwheel.util import (
+    BuildFrontend,
     BuildOptions,
     BuildSelector,
     DependencyConstraints,
@@ -184,6 +185,7 @@ def main() -> None:
 
     archs_config_str = args.archs or options("archs", sep=" ")
 
+    build_frontend_str = options("build-frontend", env_plat=False)
     environment_config = options("environment", table={"item": '{k}="{v}"', "sep": " "})
     before_all = options("before-all", sep=" && ")
     before_build = options("before-build", sep=" && ")
@@ -200,6 +202,16 @@ def main() -> None:
         os.environ.get("CIBW_PRERELEASE_PYTHONS", "0")
     )
 
+    build_frontend: BuildFrontend
+    if build_frontend_str == "build":
+        build_frontend = "build"
+    elif build_frontend_str == "pip":
+        build_frontend = "pip"
+    else:
+        msg = f"cibuildwheel: Unrecognised build frontend '{build_frontend}', only 'pip' and 'build' are supported"
+        print(msg, file=sys.stderr)
+        sys.exit(2)
+
     package_files = {"setup.py", "setup.cfg", "pyproject.toml"}
 
     if not any(package_dir.joinpath(name).exists() for name in package_files):
@@ -308,6 +320,7 @@ def main() -> None:
         environment=environment,
         dependency_constraints=dependency_constraints,
         manylinux_images=manylinux_images or None,
+        build_frontend=build_frontend,
     )
 
     # Python is buffering by default when running on the CI platforms, giving problems interleaving subprocess call output with unflushed calls to 'print'

cibuildwheel/linux.py

@@ -7,7 +7,7 @@ from typing import List, NamedTuple, Set
 from .architecture import Architecture
 from .docker_container import DockerContainer
 from .logger import log
-from .typing import PathOrStr
+from .typing import PathOrStr, assert_never
 from .util import (
     BuildOptions,
     BuildSelector,
@@ -145,7 +145,7 @@ def build(options: BuildOptions) -> None:
                         env, executor=docker.environment_executor
                     )
 
-                    # check config python and pip are still on PATH
+                    # check config python is still on PATH
                     which_python = docker.call(
                         ["which", "python"], env=env, capture_output=True
                     ).strip()
@@ -180,18 +180,38 @@ def build(options: BuildOptions) -> None:
                     docker.call(["rm", "-rf", built_wheel_dir])
                     docker.call(["mkdir", "-p", built_wheel_dir])
 
-                    docker.call(
+                    verbosity_flags = get_build_verbosity_extra_flags(options.build_verbosity)
-                        [
+
-                            "pip",
+                    if options.build_frontend == "pip":
-                            "wheel",
+                        docker.call(
-                            container_package_dir,
+                            [
-                            "--wheel-dir",
+                                "python",
-                            built_wheel_dir,
+                                "-m",
-                            "--no-deps",
+                                "pip",
-                            *get_build_verbosity_extra_flags(options.build_verbosity),
+                                "wheel",
-                        ],
+                                container_package_dir,
-                        env=env,
+                                f"--wheel-dir={built_wheel_dir}",
-                    )
+                                "--no-deps",
+                                *verbosity_flags,
+                            ],
+                            env=env,
+                        )
+                    elif options.build_frontend == "build":
+                        config_setting = " ".join(verbosity_flags)
+                        docker.call(
+                            [
+                                "python",
+                                "-m",
+                                "build",
+                                container_package_dir,
+                                "--wheel",
+                                f"--outdir={built_wheel_dir}",
+                                f"--config-setting={config_setting}",
+                            ],
+                            env=env,
+                        )
+                    else:
+                        assert_never(options.build_frontend)
 
                     built_wheel = docker.glob(built_wheel_dir, "*.whl")[0]
 
@@ -291,8 +311,11 @@ def build(options: BuildOptions) -> None:
 
 
 def troubleshoot(package_dir: Path, error: Exception) -> None:
-    if isinstance(error, subprocess.CalledProcessError) and error.cmd[0:2] == ["pip", "wheel"]:
+    if isinstance(error, subprocess.CalledProcessError) and (
-        # the 'pip wheel' step failed.
+        error.cmd[0:4] == ["python", "-m", "pip", "wheel"]
+        or error.cmd[0:3] == ["python", "-m", "build"]
+    ):
+        # the wheel build step failed
         print("Checking for common errors...")
         so_files = list(package_dir.glob("**/*.so"))
 

cibuildwheel/macos.py

@@ -12,13 +12,15 @@ from typing import Any, Dict, List, NamedTuple, Optional, Sequence, Set, Tuple,
 from .architecture import Architecture
 from .environment import ParsedEnvironment
 from .logger import log
-from .typing import Literal, PathOrStr
+from .typing import Literal, PathOrStr, assert_never
 from .util import (
+    BuildFrontend,
     BuildOptions,
     BuildSelector,
     NonPlatformWheelError,
     download,
     get_build_verbosity_extra_flags,
+    get_pip_version,
     install_certifi_script,
     prepare_command,
     read_python_configs,
@@ -178,7 +180,9 @@ def setup_python(
     python_configuration: PythonConfiguration,
     dependency_constraint_flags: Sequence[PathOrStr],
     environment: ParsedEnvironment,
+    build_frontend: BuildFrontend,
 ) -> Dict[str, str]:
+
     implementation_id = python_configuration.identifier.split("-")[0]
     log.step(f"Installing Python {implementation_id}...")
 
@@ -308,18 +312,33 @@ def setup_python(
             env.setdefault("SDKROOT", arm64_compatible_sdks[0])
 
     log.step("Installing build tools...")
-    call(
+    if build_frontend == "pip":
-        [
+        call(
-            "pip",
+            [
-            "install",
+                "pip",
-            "--upgrade",
+                "install",
-            "setuptools",
+                "--upgrade",
-            "wheel",
+                "setuptools",
-            "delocate",
+                "wheel",
-            *dependency_constraint_flags,
+                "delocate",
-        ],
+                *dependency_constraint_flags,
-        env=env,
+            ],
-    )
+            env=env,
+        )
+    elif build_frontend == "build":
+        call(
+            [
+                "pip",
+                "install",
+                "--upgrade",
+                "delocate",
+                "build[virtualenv]",
+                *dependency_constraint_flags,
+            ],
+            env=env,
+        )
+    else:
+        assert_never(build_frontend)
 
     return env
 
@@ -356,7 +375,12 @@ def build(options: BuildOptions) -> None:
                     options.dependency_constraints.get_for_python_version(config.version),
                 ]
 
-            env = setup_python(config, dependency_constraint_flags, options.environment)
+            env = setup_python(
+                config,
+                dependency_constraint_flags,
+                options.environment,
+                options.build_frontend,
+            )
 
             if options.before_build:
                 log.step("Running before_build...")
@@ -370,20 +394,46 @@ def build(options: BuildOptions) -> None:
                 shutil.rmtree(built_wheel_dir)
             built_wheel_dir.mkdir(parents=True)
 
-            # Path.resolve() is needed. Without it pip wheel may try to fetch package from pypi.org
+            verbosity_flags = get_build_verbosity_extra_flags(options.build_verbosity)
-            # see https://github.com/pypa/cibuildwheel/pull/369
+
-            call(
+            if options.build_frontend == "pip":
-                [
+                # Path.resolve() is needed. Without it pip wheel may try to fetch package from pypi.org
-                    "pip",
+                # see https://github.com/pypa/cibuildwheel/pull/369
-                    "wheel",
+                call(
-                    options.package_dir.resolve(),
+                    [
-                    "--wheel-dir",
+                        "python",
-                    built_wheel_dir,
+                        "-m",
-                    "--no-deps",
+                        "pip",
-                    *get_build_verbosity_extra_flags(options.build_verbosity),
+                        "wheel",
-                ],
+                        options.package_dir.resolve(),
-                env=env,
+                        f"--wheel-dir={built_wheel_dir}",
-            )
+                        "--no-deps",
+                        *verbosity_flags,
+                    ],
+                    env=env,
+                )
+            elif options.build_frontend == "build":
+                config_setting = " ".join(verbosity_flags)
+                build_env = env.copy()
+                if options.dependency_constraints:
+                    build_env["PIP_CONSTRAINT"] = str(
+                        options.dependency_constraints.get_for_python_version(config.version)
+                    )
+                build_env["VIRTUALENV_PIP"] = get_pip_version(env)
+                call(
+                    [
+                        "python",
+                        "-m",
+                        "build",
+                        options.package_dir,
+                        "--wheel",
+                        f"--outdir={built_wheel_dir}",
+                        f"--config-setting={config_setting}",
+                    ],
+                    env=build_env,
+                )
+            else:
+                assert_never(options.build_frontend)
 
             built_wheel = next(built_wheel_dir.glob("*.whl"))
 

cibuildwheel/resources/defaults.toml

@@ -4,6 +4,7 @@ skip = ""
 test-skip = ""
 
 archs = ["auto"]
+build-frontend = "pip"
 dependency-versions = "pinned"
 environment = {}
 build-verbosity = ""

cibuildwheel/util.py

@@ -4,6 +4,8 @@ import itertools
 import os
 import re
 import ssl
+import subprocess
+import sys
 import textwrap
 import time
 import urllib.request
@@ -20,12 +22,14 @@ from packaging.version import Version
 
 from .architecture import Architecture
 from .environment import ParsedEnvironment
-from .typing import PathOrStr, PlatformName
+from .typing import Literal, PathOrStr, PlatformName
 
 resources_dir = Path(__file__).parent / "resources"
 
 install_certifi_script = resources_dir / "install_certifi.py"
 
+BuildFrontend = Literal["pip", "build"]
+
 
 def prepare_command(command: str, **kwargs: PathOrStr) -> str:
     """
@@ -218,6 +222,7 @@ class BuildOptions(NamedTuple):
     test_requires: List[str]
     test_extras: str
     build_verbosity: int
+    build_frontend: BuildFrontend
 
 
 class NonPlatformWheelError(Exception):
@@ -300,3 +305,18 @@ def print_new_wheels(msg: str, output_dir: Path) -> Iterator[None]:
     s = time.time() - start_time
     m = s / 60
     print(msg.format(n=n, s=s, m=m), *sorted(f"  {f.name}" for f in new_contents), sep="\n")
+
+
+def get_pip_version(env: Dict[str, str]) -> str:
+    # we use shell=True here for windows, even though we don't need a shell due to a bug
+    # https://bugs.python.org/issue8557
+    shell = sys.platform.startswith("win")
+    versions_output_text = subprocess.check_output(
+        ["python", "-m", "pip", "freeze", "--all"], universal_newlines=True, shell=shell, env=env
+    )
+    (pip_version,) = (
+        version[5:]
+        for version in versions_output_text.strip().splitlines()
+        if version.startswith("pip==")
+    )
+    return pip_version

cibuildwheel/windows.py

@@ -10,13 +10,15 @@ from zipfile import ZipFile
 from .architecture import Architecture
 from .environment import ParsedEnvironment
 from .logger import log
-from .typing import PathOrStr
+from .typing import PathOrStr, assert_never
 from .util import (
+    BuildFrontend,
     BuildOptions,
     BuildSelector,
     NonPlatformWheelError,
     download,
     get_build_verbosity_extra_flags,
+    get_pip_version,
     prepare_command,
     read_python_configs,
 )
@@ -114,7 +116,9 @@ def setup_python(
     python_configuration: PythonConfiguration,
     dependency_constraint_flags: Sequence[PathOrStr],
     environment: ParsedEnvironment,
+    build_frontend: BuildFrontend,
 ) -> Dict[str, str]:
+
     nuget = Path("C:\\cibw\\nuget.exe")
     if not nuget.exists():
         log.step("Downloading nuget...")
@@ -214,10 +218,26 @@ def setup_python(
         sys.exit(1)
 
     call(["pip", "--version"], env=env)
-    call(
+
-        ["pip", "install", "--upgrade", "setuptools", "wheel", *dependency_constraint_flags],
+    if build_frontend == "pip":
-        env=env,
+        call(
-    )
+            [
+                "pip",
+                "install",
+                "--upgrade",
+                "setuptools",
+                "wheel",
+                *dependency_constraint_flags,
+            ],
+            env=env,
+        )
+    elif build_frontend == "build":
+        call(
+            ["pip", "install", "--upgrade", "build[virtualenv]", *dependency_constraint_flags],
+            env=env,
+        )
+    else:
+        assert_never(build_frontend)
 
     return env
 
@@ -251,7 +271,12 @@ def build(options: BuildOptions) -> None:
                 ]
 
             # install Python
-            env = setup_python(config, dependency_constraint_flags, options.environment)
+            env = setup_python(
+                config,
+                dependency_constraint_flags,
+                options.environment,
+                options.build_frontend,
+            )
 
             # run the before_build command
             if options.before_build:
@@ -265,20 +290,47 @@ def build(options: BuildOptions) -> None:
             if built_wheel_dir.exists():
                 shutil.rmtree(built_wheel_dir)
             built_wheel_dir.mkdir(parents=True)
-            # Path.resolve() is needed. Without it pip wheel may try to fetch package from pypi.org
+
-            # see https://github.com/pypa/cibuildwheel/pull/369
+            verbosity_flags = get_build_verbosity_extra_flags(options.build_verbosity)
-            call(
+
-                [
+            if options.build_frontend == "pip":
-                    "pip",
+                # Path.resolve() is needed. Without it pip wheel may try to fetch package from pypi.org
-                    "wheel",
+                # see https://github.com/pypa/cibuildwheel/pull/369
-                    options.package_dir.resolve(),
+                call(
-                    "-w",
+                    [
-                    built_wheel_dir,
+                        "python",
-                    "--no-deps",
+                        "-m",
-                    *get_build_verbosity_extra_flags(options.build_verbosity),
+                        "pip",
-                ],
+                        "wheel",
-                env=env,
+                        options.package_dir.resolve(),
-            )
+                        f"--wheel-dir={built_wheel_dir}",
+                        "--no-deps",
+                        *get_build_verbosity_extra_flags(options.build_verbosity),
+                    ],
+                    env=env,
+                )
+            elif options.build_frontend == "build":
+                config_setting = " ".join(verbosity_flags)
+                build_env = env.copy()
+                if options.dependency_constraints:
+                    build_env["PIP_CONSTRAINT"] = str(
+                        options.dependency_constraints.get_for_python_version(config.version)
+                    )
+                build_env["VIRTUALENV_PIP"] = get_pip_version(env)
+                call(
+                    [
+                        "python",
+                        "-m",
+                        "build",
+                        options.package_dir,
+                        "--wheel",
+                        f"--outdir={built_wheel_dir}",
+                        f"--config-setting={config_setting}",
+                    ],
+                    env=build_env,
+                )
+            else:
+                assert_never(options.build_frontend)
 
             built_wheel = next(built_wheel_dir.glob("*.whl"))
 

docs/faq.md

@@ -210,7 +210,7 @@ There are two suggested methods for keeping cibuildwheel up to date that instead
 If you use GitHub Actions for builds, you can use cibuildwheel as an action:
 
 ```yaml
-uses: pypa/cibuildwheel@v2.0.0a3
+uses: pypa/cibuildwheel@v2.0.0a4
 ```
 
 This is a composite step that just runs cibuildwheel using pipx. You can set command-line options as `with:` parameters, and use `env:` as normal.
@@ -236,7 +236,7 @@ The second option, and the only one that supports other CI systems, is using a `
 
 ```bash
 # requirements-cibw.txt
-cibuildwheel==2.0.0a3
+cibuildwheel==2.0.0a4
 ```
 
 Then your install step would have `python -m pip install -r requirements-cibw.txt` in it. Your `dependabot.yml` file could look like this:

docs/options.md

@@ -155,7 +155,7 @@ When setting the options, you can use shell-style globbing syntax, as per [fnmat
 |--------------|---------------------------------------------------------------------|-------------------------------|-----------------------------------------------|----------------------------------------------------------------------------|
 | Python 3.6   | cp36-macosx_x86_64                                                  | cp36-win_amd64<br/>cp36-win32 | cp36-manylinux_x86_64<br/>cp36-manylinux_i686 | cp36-manylinux_aarch64<br/>cp36-manylinux_ppc64le<br/>cp36-manylinux_s390x |
 | Python 3.7   | cp37-macosx_x86_64                                                  | cp37-win_amd64<br/>cp37-win32 | cp37-manylinux_x86_64<br/>cp37-manylinux_i686 | cp37-manylinux_aarch64<br/>cp37-manylinux_ppc64le<br/>cp37-manylinux_s390x |
-| Python 3.8   | cp38-macosx_x86_64                                                  | cp38-win_amd64<br/>cp38-win32 | cp38-manylinux_x86_64<br/>cp38-manylinux_i686 | cp38-manylinux_aarch64<br/>cp38-manylinux_ppc64le<br/>cp38-manylinux_s390x |
+| Python 3.8   | cp38-macosx_x86_64<br/>cp38-macosx_universal2<br/>cp38-macosx_arm64 | cp38-win_amd64<br/>cp38-win32 | cp38-manylinux_x86_64<br/>cp38-manylinux_i686 | cp38-manylinux_aarch64<br/>cp38-manylinux_ppc64le<br/>cp38-manylinux_s390x |
 | Python 3.9   | cp39-macosx_x86_64<br/>cp39-macosx_universal2<br/>cp39-macosx_arm64 | cp39-win_amd64<br/>cp39-win32 | cp39-manylinux_x86_64<br/>cp39-manylinux_i686 | cp39-manylinux_aarch64<br/>cp39-manylinux_ppc64le<br/>cp39-manylinux_s390x |
 | PyPy3.7 v7.3 | pp37-macosx_x86_64                                                  |                pp37-win_amd64 | pp37-manylinux_x86_64                         |                                                                            |
 
@@ -435,6 +435,45 @@ This option can also be set using the [command-line option](#command-line) `--pr
 
 ## Build customization
 
+### `CIBW_BUILD_FRONTEND` {: #build-frontend}
+> Set the tool to use to build, either "pip" (default for now) or "build"
+
+Choose which build backend to use. Can either be "pip", which will run
+`python -m pip wheel`, or "build", which will run `python -m build --wheel`.
+
+!!! tip
+    Until v2.0.0, [pip] was the only way to build wheels, and is still the
+    default. However, we expect that at some point in the future, cibuildwheel
+    will change the default to [build], in line with the PyPA's recommendation.
+    If you want to try `build` before this, you can use this option.
+
+[pip]: https://pip.pypa.io/en/stable/cli/pip_wheel/
+[build]: https://github.com/pypa/build/
+
+#### Examples
+
+!!! tab examples "Environment variables"
+
+    ```yaml
+    # Switch to using build
+    CIBW_BUILD_FRONTEND: "build"
+
+    # Ensure pip is used even if the default changes in the future
+    CIBW_BUILD_FRONTEND: "pip"
+    ```
+
+!!! tab examples "pyproject.toml"
+
+    ```toml
+    [tool.cibuildwheel]
+    # Switch to using build
+    build-frontend = "build"
+
+    # Ensure pip is used even if the default changes in the future
+    build-frontend = "pip"
+    ```
+
+
 ### `CIBW_ENVIRONMENT` {: #environment}
 > Set environment variables needed during the build
 

docs/setup.md

@@ -46,7 +46,7 @@ To build Linux, Mac, and Windows wheels using GitHub Actions, create a `.github/
           - uses: actions/checkout@v2
 
           - name: Build wheels
-            run: pipx run cibuildwheel==2.0.0a3
+            run: pipx run cibuildwheel==2.0.0a4
 
           - uses: actions/upload-artifact@v2
             with:
@@ -81,7 +81,7 @@ To build Linux, Mac, and Windows wheels using GitHub Actions, create a `.github/
           - uses: actions/setup-python@v2
 
           - name: Install cibuildwheel
-            run: python -m pip install cibuildwheel==2.0.0a3
+            run: python -m pip install cibuildwheel==2.0.0a4
 
           - name: Build wheels
             run: python -m cibuildwheel --output-dir wheelhouse

examples/appveyor-minimal.yml

@@ -12,7 +12,7 @@ stack: python 3.7
 init:
 - cmd: set PATH=C:\Python37;C:\Python37\Scripts;%PATH%
 
-install: python -m pip install cibuildwheel==2.0.0a3
+install: python -m pip install cibuildwheel==2.0.0a4
 
 build_script: python -m cibuildwheel --output-dir wheelhouse
 

examples/azure-pipelines-minimal.yml

@@ -6,7 +6,7 @@ jobs:
     - bash: |
         set -o errexit
         python3 -m pip install --upgrade pip
-        pip3 install cibuildwheel==2.0.0a3
+        pip3 install cibuildwheel==2.0.0a4
       displayName: Install dependencies
     - bash: cibuildwheel --output-dir wheelhouse .
       displayName: Build wheels
@@ -20,7 +20,7 @@ jobs:
     - bash: |
         set -o errexit
         python3 -m pip install --upgrade pip
-        python3 -m pip install cibuildwheel==2.0.0a3
+        python3 -m pip install cibuildwheel==2.0.0a4
       displayName: Install dependencies
     - bash: cibuildwheel --output-dir wheelhouse .
       displayName: Build wheels
@@ -34,7 +34,7 @@ jobs:
     - bash: |
         set -o errexit
         python -m pip install --upgrade pip
-        pip install cibuildwheel==2.0.0a3
+        pip install cibuildwheel==2.0.0a4
       displayName: Install dependencies
     - bash: cibuildwheel --output-dir wheelhouse .
       displayName: Build wheels

examples/circleci-minimal.yml

@@ -11,7 +11,7 @@ jobs:
       - run:
           name: Build the Linux wheels.
           command: |
-            pip3 install --user cibuildwheel==2.0.0a3
+            pip3 install --user cibuildwheel==2.0.0a4
             cibuildwheel --output-dir wheelhouse
       - store_artifacts:
           path: wheelhouse/
@@ -25,7 +25,7 @@ jobs:
       - run:
           name: Build the OS X wheels.
           command: |
-            pip3 install cibuildwheel==2.0.0a3
+            pip3 install cibuildwheel==2.0.0a4
             cibuildwheel --output-dir wheelhouse
       - store_artifacts:
           path: wheelhouse/

examples/github-apple-silicon.yml

@@ -10,7 +10,7 @@ jobs:
       - uses: actions/checkout@v2
 
       - name: Build wheels
-        uses: pypa/cibuildwheel@v2.0.0a3
+        uses: pypa/cibuildwheel@v2.0.0a4
         env:
           CIBW_ARCHS_MACOS: x86_64 universal2
 

examples/github-deploy.yml

@@ -27,7 +27,7 @@ jobs:
           python-version: '3.8'
 
       - name: Build wheels
-        uses: pypa/cibuildwheel@v2.0.0a3
+        uses: pypa/cibuildwheel@v2.0.0a4
 
       - uses: actions/upload-artifact@v2
         with:

examples/github-minimal.yml

@@ -14,7 +14,7 @@ jobs:
       - uses: actions/checkout@v2
 
       - name: Build wheels
-        uses: pypa/cibuildwheel@v2.0.0a3
+        uses: pypa/cibuildwheel@v2.0.0a4
         # to supply options, put them in 'env', like:
         # env:
         #   CIBW_SOME_OPTION: value

examples/github-with-qemu.yml

@@ -25,7 +25,7 @@ jobs:
           platforms: all
 
       - name: Build wheels
-        uses: pypa/cibuildwheel@v2.0.0a3
+        uses: pypa/cibuildwheel@v2.0.0a4
         env:
           # configure cibuildwheel to build native archs ('auto'), and some
           # emulated ones

examples/gitlab-minimal.yml

@@ -12,7 +12,7 @@ linux:
     DOCKER_TLS_CERTDIR: ""
   script:
     - curl -sSL https://get.docker.com/ | sh
-    - python -m pip install cibuildwheel==2.0.0a3
+    - python -m pip install cibuildwheel==2.0.0a4
     - cibuildwheel --output-dir wheelhouse
   artifacts:
     paths:

examples/travis-ci-deploy.yml

@@ -19,7 +19,7 @@ jobs:
         - ln -s /c/Python38/python.exe /c/Python38/python3.exe
 
 install:
-  - python3 -m pip install cibuildwheel==2.0.0a3
+  - python3 -m pip install cibuildwheel==2.0.0a4
 
 script:
   # build the wheels, put them into './wheelhouse'

examples/travis-ci-minimal.yml

@@ -25,7 +25,7 @@ jobs:
         - ln -s /c/Python38/python.exe /c/Python38/python3.exe
 
 install:
-  - python3 -m pip install cibuildwheel==2.0.0a3
+  - python3 -m pip install cibuildwheel==2.0.0a4
 
 script:
   # build the wheels, put them into './wheelhouse'

examples/travis-ci-test-and-deploy.yml

@@ -57,7 +57,7 @@ jobs:
     - stage: deploy
       name: Build and deploy Linux wheels
       services: docker
-      install: python3 -m pip install cibuildwheel==2.0.0a3
+      install: python3 -m pip install cibuildwheel==2.0.0a4
       script: python3 -m cibuildwheel --output-dir wheelhouse
       after_success: |
         python3 -m pip install twine
@@ -67,7 +67,7 @@ jobs:
       name: Build and deploy Windows wheels
       os: windows
       language: shell
-      install: python3 -m pip install cibuildwheel==2.0.0a3
+      install: python3 -m pip install cibuildwheel==2.0.0a4
       script: python3 -m cibuildwheel --output-dir wheelhouse
       after_success: |
         python3 -m pip install twine

setup.cfg

@@ -1,6 +1,6 @@
 [metadata]
 name = cibuildwheel
-version = 2.0.0a3
+version = 2.0.0a4
 description = Build Python wheels on CI with minimal configuration.
 long_description = file: README.md
 long_description_content_type = text/markdown

test/conftest.py

@@ -1,7 +1,9 @@
+from typing import Dict
+
 import pytest
 
 
-def pytest_addoption(parser):
+def pytest_addoption(parser) -> None:
     parser.addoption(
         "--run-emulation", action="store_true", default=False, help="run emulation tests"
     )
@@ -11,7 +13,7 @@ def pytest_configure(config):
     config.addinivalue_line("markers", "emulation: mark test requiring qemu binfmt_misc to run")
 
 
-def pytest_collection_modifyitems(config, items):
+def pytest_collection_modifyitems(config, items) -> None:
     if config.getoption("--run-emulation"):
         # --run-emulation given in cli: do not skip emulation tests
         return
@@ -19,3 +21,10 @@ def pytest_collection_modifyitems(config, items):
     for item in items:
         if "emulation" in item.keywords:
             item.add_marker(skip_emulation)
+
+
+@pytest.fixture(
+    params=[{"CIBW_BUILD_FRONTEND": "pip"}, {"CIBW_BUILD_FRONTEND": "build"}], ids=["pip", "build"]
+)
+def build_frontend_env(request) -> Dict[str, str]:
+    return request.param  # type: ignore

test/test_0_basic.py

@@ -18,12 +18,12 @@ basic_project = test_projects.new_c_project(
 )
 
 
-def test(tmp_path):
+def test(tmp_path, build_frontend_env):
     project_dir = tmp_path / "project"
     basic_project.generate(project_dir)
 
     # build the wheels
-    actual_wheels = utils.cibuildwheel_run(project_dir)
+    actual_wheels = utils.cibuildwheel_run(project_dir, add_env=build_frontend_env)
 
     # check that the expected wheels are produced
     expected_wheels = utils.expected_wheels("spam", "0.1.0")

test/test_before_build.py

@@ -25,8 +25,13 @@ project_with_before_build_asserts = test_projects.new_c_project(
             stored_executable = f.read()
         print('stored_executable', stored_executable)
         print('sys.executable', sys.executable)
+
         # windows/mac are case insensitive
-        assert os.path.realpath(stored_executable).lower() == os.path.realpath(sys.executable).lower()
+        stored_path = os.path.realpath(stored_executable).lower()
+        current_path = os.path.realpath(sys.executable).lower()
+
+        # TODO: This is not valid in an virtual environment
+        assert stored_path == current_path, '{0} != {1}'.format(stored_path, current_path)
         """
     )
 )

test/test_dependency_versions.py

@@ -48,7 +48,7 @@ def get_versions_from_constraint_file(constraint_file):
 
 
 @pytest.mark.parametrize("python_version", ["3.6", "3.8", "3.9"])
-def test_pinned_versions(tmp_path, python_version):
+def test_pinned_versions(tmp_path, python_version, build_frontend_env):
     if utils.platform == "linux":
         pytest.skip("linux doesn't pin individual tool versions, it pins manylinux images instead")
 
@@ -85,6 +85,7 @@ def test_pinned_versions(tmp_path, python_version):
         add_env={
             "CIBW_BUILD": build_pattern,
             "CIBW_ENVIRONMENT": cibw_environment_option,
+            **build_frontend_env,
         },
     )
 
@@ -107,7 +108,7 @@ def test_pinned_versions(tmp_path, python_version):
     assert set(actual_wheels) == set(expected_wheels)
 
 
-def test_dependency_constraints_file(tmp_path):
+def test_dependency_constraints_file(tmp_path, build_frontend_env):
     if utils.platform == "linux":
         pytest.skip("linux doesn't pin individual tool versions, it pins manylinux images instead")
 
@@ -118,7 +119,7 @@ def test_dependency_constraints_file(tmp_path):
         "pip": "20.0.2",
         "setuptools": "53.0.0",
         "wheel": "0.34.2",
-        "virtualenv": "20.0.10",
+        "virtualenv": "20.0.35",
     }
 
     constraints_file = tmp_path / "constraints.txt"
@@ -129,6 +130,7 @@ def test_dependency_constraints_file(tmp_path):
             setuptools=={setuptools}
             wheel=={wheel}
             virtualenv=={virtualenv}
+            importlib-metadata<3,>=0.12; python_version < "3.8"
             """.format(
                 **tool_versions
             )
@@ -149,6 +151,7 @@ def test_dependency_constraints_file(tmp_path):
         add_env={
             "CIBW_ENVIRONMENT": cibw_environment_option,
             "CIBW_DEPENDENCY_VERSIONS": str(constraints_file),
+            **build_frontend_env,
         },
     )
 

test/test_pep518.py

@@ -1,4 +1,3 @@
-import os
 import textwrap
 
 from . import test_projects, utils
@@ -33,13 +32,13 @@ build-backend = "setuptools.build_meta"
 """
 
 
-def test_pep518(tmp_path):
+def test_pep518(tmp_path, build_frontend_env):
 
     project_dir = tmp_path / "project"
     basic_project.generate(project_dir)
 
     # build the wheels
-    actual_wheels = utils.cibuildwheel_run(project_dir)
+    actual_wheels = utils.cibuildwheel_run(project_dir, add_env=build_frontend_env)
 
     # check that the expected wheels are produced
     expected_wheels = utils.expected_wheels("spam", "0.1.0")
@@ -50,4 +49,12 @@ def test_pep518(tmp_path):
     assert not (project_dir / "42").exists()
     assert not (project_dir / "4.1.2").exists()
 
-    assert len(os.listdir(project_dir)) == len(basic_project.files)
+    # pypa/build creates a "build" folder & a "*.egg-info" folder for the wheel being built,
+    # this should be harmless so remove them
+    contents = [
+        item
+        for item in project_dir.iterdir()
+        if item.name != "build" and not item.name.endswith(".egg-info")
+    ]
+
+    assert len(contents) == len(basic_project.files)

test/test_troubleshooting.py

@@ -16,7 +16,7 @@ raise Exception('this build will fail')
 """
 
 
-def test_failed_project_with_so_files(tmp_path, capfd):
+def test_failed_project_with_so_files(tmp_path, capfd, build_frontend_env):
     if utils.platform != "linux":
         pytest.skip("this test is only relevant to the linux build")
 
@@ -24,7 +24,7 @@ def test_failed_project_with_so_files(tmp_path, capfd):
     so_file_project.generate(project_dir)
 
     with pytest.raises(subprocess.CalledProcessError):
-        utils.cibuildwheel_run(project_dir)
+        utils.cibuildwheel_run(project_dir, add_env=build_frontend_env)
 
     captured = capfd.readouterr()
     print("out", captured.out)