fix: respect constraints when building with pip (#1818)

When building a project that has a `pyproject.toml`, constraints
are not respected when building with the `pip` frontend.

This commit fixes this by using the same tricks as for the `build` frontend.

cibuildwheel/macos.py

@@ -381,6 +381,18 @@ def build(options: Options, tmp_path: Path) -> None:
                 )
                 extra_flags += build_frontend.args
 
+                build_env = env.copy()
+                build_env["VIRTUALENV_PIP"] = get_pip_version(env)
+                if build_options.dependency_constraints:
+                    constraint_path = build_options.dependency_constraints.get_for_python_version(
+                        config.version
+                    )
+                    user_constraints = build_env.get("PIP_CONSTRAINT")
+                    our_constraints = constraint_path.as_uri()
+                    build_env["PIP_CONSTRAINT"] = " ".join(
+                        c for c in [user_constraints, our_constraints] if c
+                    )
+
                 if build_frontend.name == "pip":
                     extra_flags += get_build_verbosity_extra_flags(build_options.build_verbosity)
                     # Path.resolve() is needed. Without it pip wheel may try to fetch package from pypi.org
@@ -394,25 +406,12 @@ def build(options: Options, tmp_path: Path) -> None:
                         f"--wheel-dir={built_wheel_dir}",
                         "--no-deps",
                         *extra_flags,
-                        env=env,
+                        env=build_env,
                     )
                 elif build_frontend.name == "build":
                     if not 0 <= build_options.build_verbosity < 2:
                         msg = f"build_verbosity {build_options.build_verbosity} is not supported for build frontend. Ignoring."
                         log.warning(msg)
-                    build_env = env.copy()
-                    if build_options.dependency_constraints:
-                        constraint_path = (
-                            build_options.dependency_constraints.get_for_python_version(
-                                config.version
-                            )
-                        )
-                        user_constraints = build_env.get("PIP_CONSTRAINT")
-                        our_constraints = constraint_path.as_uri()
-                        build_env["PIP_CONSTRAINT"] = " ".join(
-                            c for c in [user_constraints, our_constraints] if c
-                        )
-                    build_env["VIRTUALENV_PIP"] = get_pip_version(env)
                     call(
                         "python",
                         "-m",

cibuildwheel/windows.py

@@ -407,32 +407,12 @@ def build(options: Options, tmp_path: Path) -> None:
                 )
                 extra_flags += build_frontend.args
 
-                if build_frontend.name == "pip":
-                    extra_flags += get_build_verbosity_extra_flags(build_options.build_verbosity)
-                    # Path.resolve() is needed. Without it pip wheel may try to fetch package from pypi.org
-                    # see https://github.com/pypa/cibuildwheel/pull/369
-                    call(
-                        "python",
-                        "-m",
-                        "pip",
-                        "wheel",
-                        options.globals.package_dir.resolve(),
-                        f"--wheel-dir={built_wheel_dir}",
-                        "--no-deps",
-                        *extra_flags,
-                        env=env,
-                    )
-                elif build_frontend.name == "build":
-                    if not 0 <= build_options.build_verbosity < 2:
-                        msg = f"build_verbosity {build_options.build_verbosity} is not supported for build frontend. Ignoring."
-                        log.warning(msg)
                 build_env = env.copy()
+                build_env["VIRTUALENV_PIP"] = get_pip_version(env)
                 if build_options.dependency_constraints:
-                        constraints_path = (
+                    constraints_path = build_options.dependency_constraints.get_for_python_version(
-                            build_options.dependency_constraints.get_for_python_version(
                         config.version
                     )
-                        )
                     # Bug in pip <= 21.1.3 - we can't have a space in the
                     # constraints file, and pip doesn't support drive letters
                     # in uhi.  After probably pip 21.2, we can use uri. For
@@ -449,7 +429,25 @@ def build(options: Options, tmp_path: Path) -> None:
                         c for c in [our_constraints, user_constraints] if c
                     )
 
-                        build_env["VIRTUALENV_PIP"] = get_pip_version(env)
+                if build_frontend.name == "pip":
+                    extra_flags += get_build_verbosity_extra_flags(build_options.build_verbosity)
+                    # Path.resolve() is needed. Without it pip wheel may try to fetch package from pypi.org
+                    # see https://github.com/pypa/cibuildwheel/pull/369
+                    call(
+                        "python",
+                        "-m",
+                        "pip",
+                        "wheel",
+                        options.globals.package_dir.resolve(),
+                        f"--wheel-dir={built_wheel_dir}",
+                        "--no-deps",
+                        *extra_flags,
+                        env=build_env,
+                    )
+                elif build_frontend.name == "build":
+                    if not 0 <= build_options.build_verbosity < 2:
+                        msg = f"build_verbosity {build_options.build_verbosity} is not supported for build frontend. Ignoring."
+                        log.warning(msg)
                     call(
                         "python",
                         "-m",

test/test_dependency_versions.py

@@ -15,9 +15,10 @@ project_with_expected_version_checks = test_projects.new_c_project(
         r"""
         import subprocess
         import os
+        import sys
 
         versions_output_text = subprocess.check_output(
-            ['pip', 'freeze', '--all', '-qq'],
+            [sys.executable, '-m', 'pip', 'freeze', '--all', '-qq'],
             universal_newlines=True,
         )
         versions = versions_output_text.strip().splitlines()
@@ -36,6 +37,11 @@ project_with_expected_version_checks = test_projects.new_c_project(
     )
 )
 
+project_with_expected_version_checks.files["pyproject.toml"] = r"""
+[build-system]
+requires = ["setuptools", "pip"]
+build-backend = "setuptools.build_meta"
+"""
 
 VERSION_REGEX = r"([\w-]+)==([^\s]+)"
 
@@ -50,27 +56,16 @@ def get_versions_from_constraint_file(constraint_file):
 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")
+    if python_version == "3.6" and utils.platform == "macos" and platform.machine() == "arm64":
+        pytest.skip("macOS arm64 does not support Python 3.6")
 
     project_dir = tmp_path / "project"
     project_with_expected_version_checks.generate(project_dir)
 
+    version_no_dot = python_version.replace(".", "")
     build_environment = {}
-
+    build_pattern = f"[cp]p{version_no_dot}-*"
-    if python_version == "3.6":
+    constraint_filename = f"constraints-python{version_no_dot}.txt"
-        if utils.platform == "macos" and platform.machine() == "arm64":
-            pytest.skip("macOS arm64 does not support Python 3.6")
-        constraint_filename = "constraints-python36.txt"
-        build_pattern = "[cp]p36-*"
-    elif python_version == "3.7":
-        constraint_filename = "constraints-python37.txt"
-        build_pattern = "[cp]p37-*"
-    elif python_version == "3.8":
-        constraint_filename = "constraints-python38.txt"
-        build_pattern = "[cp]p38-*"
-    else:
-        constraint_filename = "constraints-python310.txt"
-        build_pattern = "[cp]p310-*"
-
     constraint_file = cibuildwheel.util.resources_dir / constraint_filename
     constraint_versions = get_versions_from_constraint_file(constraint_file)
 
@@ -89,21 +84,11 @@ def test_pinned_versions(tmp_path, python_version, build_frontend_env):
     )
 
     # also check that we got the right wheels
-    if python_version == "3.6":
     expected_wheels = [
-            w for w in utils.expected_wheels("spam", "0.1.0") if "-cp36" in w or "-pp36" in w
+        w
+        for w in utils.expected_wheels("spam", "0.1.0")
+        if f"-cp{version_no_dot}" in w or f"-pp{version_no_dot}" in w
     ]
-    elif python_version == "3.8":
-        expected_wheels = [
-            w for w in utils.expected_wheels("spam", "0.1.0") if "-cp38" in w or "-pp38" in w
-        ]
-    elif python_version == "3.10":
-        expected_wheels = [
-            w for w in utils.expected_wheels("spam", "0.1.0") if "-cp310" in w or "-pp310" in w
-        ]
-    else:
-        msg = "unhandled python version"
-        raise ValueError(msg)
 
     assert set(actual_wheels) == set(expected_wheels)