chore: refactor cibuildwheel.utils (#2252)

* chore: refactor cibuildwheel.utils

* rework build_frontend extra flags

* ci(fix): use tonistiigi/binfmt:qemu-v8.1.5 image for qemu

cibuildwheel/venv.py

@@ -0,0 +1,159 @@
+from __future__ import annotations
+
+import contextlib
+import functools
+import os
+import shutil
+import sys
+import tomllib
+from collections.abc import Sequence
+from pathlib import Path
+from typing import Final
+
+from filelock import FileLock
+from packaging.requirements import InvalidRequirement, Requirement
+from packaging.version import Version
+
+from .typing import PathOrStr
+from .util import resources
+from .util.cmd import call
+from .util.file import CIBW_CACHE_PATH, download
+
+_IS_WIN: Final[bool] = sys.platform.startswith("win")
+
+
+@functools.cache
+def _ensure_virtualenv(version: str) -> Path:
+    version_parts = version.split(".")
+    key = f"py{version_parts[0]}{version_parts[1]}"
+    with resources.VIRTUALENV.open("rb") as f:
+        loaded_file = tomllib.load(f)
+    configuration = loaded_file.get(key, loaded_file["default"])
+    version = str(configuration["version"])
+    url = str(configuration["url"])
+    path = CIBW_CACHE_PATH / f"virtualenv-{version}.pyz"
+    with FileLock(str(path) + ".lock"):
+        if not path.exists():
+            download(url, path)
+    return path
+
+
+def _parse_constraints_for_virtualenv(
+    seed_packages: list[str],
+    dependency_constraint_flags: Sequence[PathOrStr],
+) -> dict[str, str]:
+    """
+    Parses the constraints file referenced by `dependency_constraint_flags` and returns a dict where
+    the key is the package name, and the value is the constraint version.
+    If a package version cannot be found, its value is "embed" meaning that virtualenv will install
+    its bundled version, already available locally.
+    The function does not try to be too smart and just handles basic constraints.
+    If it can't get an exact version, the real constraint will be handled by the
+    {macos|windows}.setup_python function.
+    """
+    assert len(dependency_constraint_flags) in {0, 2}
+    # only seed pip if other seed packages do not appear in a constraint file
+    constraints_dict = {"pip": "embed"}
+    if len(dependency_constraint_flags) == 2:
+        assert dependency_constraint_flags[0] == "-c"
+        constraint_path = Path(dependency_constraint_flags[1])
+        assert constraint_path.exists()
+        with constraint_path.open(encoding="utf-8") as constraint_file:
+            for line_ in constraint_file:
+                line = line_.strip()
+                if not line:
+                    continue
+                if line.startswith("#"):
+                    continue
+                try:
+                    requirement = Requirement(line)
+                    package = requirement.name
+                    if (
+                        package not in seed_packages
+                        or requirement.url is not None
+                        or requirement.marker is not None
+                        or len(requirement.extras) != 0
+                        or len(requirement.specifier) != 1
+                    ):
+                        continue
+                    specifier = next(iter(requirement.specifier))
+                    if specifier.operator != "==":
+                        continue
+                    constraints_dict[package] = specifier.version
+                except InvalidRequirement:
+                    continue
+    return constraints_dict
+
+
+def virtualenv(
+    version: str,
+    python: Path,
+    venv_path: Path,
+    dependency_constraint_flags: Sequence[PathOrStr],
+    *,
+    use_uv: bool,
+) -> dict[str, str]:
+    """
+    Create a virtual environment. If `use_uv` is True,
+    dependency_constraint_flags are ignored since nothing is installed in the
+    venv. Otherwise, pip is installed, and setuptools + wheel if Python < 3.12.
+    """
+    assert python.exists()
+
+    if use_uv:
+        call("uv", "venv", venv_path, "--python", python)
+    else:
+        virtualenv_app = _ensure_virtualenv(version)
+        allowed_seed_packages = ["pip", "setuptools", "wheel"]
+        constraints = _parse_constraints_for_virtualenv(
+            allowed_seed_packages, dependency_constraint_flags
+        )
+        additional_flags: list[str] = []
+        for package in allowed_seed_packages:
+            if package in constraints:
+                additional_flags.append(f"--{package}={constraints[package]}")
+            else:
+                additional_flags.append(f"--no-{package}")
+
+        # Using symlinks to pre-installed seed packages is really the fastest way to get a virtual
+        # environment. The initial cost is a bit higher but reusing is much faster.
+        # Windows does not always allow symlinks so just disabling for now.
+        # Requires pip>=19.3 so disabling for "embed" because this means we don't know what's the
+        # version of pip that will end-up installed.
+        # c.f. https://virtualenv.pypa.io/en/latest/cli_interface.html#section-seeder
+        if (
+            not _IS_WIN
+            and constraints["pip"] != "embed"
+            and Version(constraints["pip"]) >= Version("19.3")
+        ):
+            additional_flags.append("--symlink-app-data")
+
+        call(
+            sys.executable,
+            "-sS",  # just the stdlib, https://github.com/pypa/virtualenv/issues/2133#issuecomment-1003710125
+            virtualenv_app,
+            "--activators=",
+            "--no-periodic-update",
+            *additional_flags,
+            "--python",
+            python,
+            venv_path,
+        )
+
+    paths = [str(venv_path), str(venv_path / "Scripts")] if _IS_WIN else [str(venv_path / "bin")]
+    env = os.environ.copy()
+    env["PATH"] = os.pathsep.join([*paths, env["PATH"]])
+    env["VIRTUAL_ENV"] = str(venv_path)
+    return env
+
+
+def find_uv() -> Path | None:
+    # Prefer uv in our environment
+    with contextlib.suppress(ImportError, FileNotFoundError):
+        # pylint: disable-next=import-outside-toplevel
+        from uv import find_uv_bin
+
+        return Path(find_uv_bin())
+
+    uv_on_path = shutil.which("uv")
+    return Path(uv_on_path) if uv_on_path else None