codex/scripts/setup_dev_execpolicy.py

#!/usr/bin/env python3
"""Print host executable pins for Codex development commands."""

from collections.abc import Callable
from collections.abc import Mapping
from collections.abc import Sequence
import json
import os
from pathlib import Path
import shutil
import sys


# Keep this explicit: justfile recipes can delegate to scripts that invoke other tools.
HOST_EXECUTABLES = ("cargo", "just", "bazel", "pnpm")
GENERATED_HEADER = "# Generated by scripts/setup_dev_execpolicy.py. Do not edit."
WINDOWS_EXECUTABLE_SUFFIXES = (".exe", ".cmd", ".bat", ".com")


def executable_lookup_name(path: Path, *, windows: bool = os.name == "nt") -> str:
    name = path.name
    if not windows:
        return name

    name = name.lower()
    for suffix in WINDOWS_EXECUTABLE_SUFFIXES:
        if name.endswith(suffix):
            return name[: -len(suffix)]
    return name


def absolute_without_resolving(path: str) -> Path:
    return Path(os.path.abspath(os.path.expanduser(path)))


def discover_host_executables(
    names: Sequence[str] = HOST_EXECUTABLES,
    *,
    which: Callable[[str], str | None] = shutil.which,
) -> dict[str, Path]:
    executables: dict[str, Path] = {}
    missing: list[str] = []

    for name in names:
        raw_path = which(name)
        if raw_path is None:
            missing.append(name)
            continue

        path = absolute_without_resolving(raw_path)
        if executable_lookup_name(path) != executable_lookup_name(Path(name)):
            raise RuntimeError(
                f"resolved path for {name!r} must retain that executable name: {path}"
            )
        executables[name] = path

    if missing:
        raise RuntimeError(
            "missing required host executables on PATH: " + ", ".join(missing)
        )
    return executables


def render_host_executable_rules(executables: Mapping[str, Path]) -> str:
    blocks = []
    for name, path in executables.items():
        blocks.append(
            "\n".join(
                [
                    "host_executable(",
                    f"    name = {json.dumps(name)},",
                    f"    paths = [{json.dumps(str(path))}],",
                    ")",
                ]
            )
        )
    return f"{GENERATED_HEADER}\n\n" + "\n\n".join(blocks) + "\n"


def main() -> int:
    try:
        executables = discover_host_executables()
    except RuntimeError as error:
        print(f"error: {error}", file=sys.stderr)
        return 1

    sys.stdout.write(render_host_executable_rules(executables))
    return 0


if __name__ == "__main__":
    raise SystemExit(main())