third_party/mesa/mesa_action.py

#!/usr/bin/env python3
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"""Helper wrapper for Mesa GN and CMake codegen actions.

This script serves three roles for the native GN and CMake Mesa builds:
1. Bridging to vpython3 (--vpython-spec): Dawn's root .gn configures
   `script_executable` to use the bare hermetic CPython interpreter
   (//third_party/cpython3/host/bin/python3), which does not automatically load
   Dawn's root `vpython.toml`. Similarly, CMake invokes `${Python3_EXECUTABLE}`
   directly. Mesa's Python codegen scripts require third-party packages like
   `mako` and `pyyaml` defined in `vpython.toml`, so this wrapper re-invokes
   them under `vpython3 -vpython-spec`.
2. Running compiled build-time tools: GN `action()` targets can only execute a
   Python script directly, so this wrapper is also used to invoke compiled host
   binaries such as `glslang_validator`.
3. Capturing stdout (--capture-stdout): Several upstream Mesa codegen scripts
   print generated C/header source directly to stdout instead of accepting an
   output file flag. When `--capture-stdout <path>` is passed, this script
   captures the command's stdout and writes it to `<path>` only on success.
"""

import argparse
import os
import subprocess
import sys


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument("--capture-stdout",
                        help="Write command stdout to this file")
    parser.add_argument("--vpython-spec",
                        help="Run command via vpython3 with this spec")
    parser.add_argument("cmd", nargs=argparse.REMAINDER)
    args = parser.parse_args()

    cmd = args.cmd
    if cmd and cmd[0] == "--":
        cmd = cmd[1:]
    if not cmd:
        print("Error: no command specified", file=sys.stderr)
        return 1

    if args.vpython_spec:
        cmd = ["vpython3", "-vpython-spec", args.vpython_spec] + cmd

    if args.capture_stdout:
        res = subprocess.run(cmd, stdout=subprocess.PIPE)
        if res.returncode != 0:
            return res.returncode
        os.makedirs(
            os.path.dirname(os.path.abspath(args.capture_stdout)),
            exist_ok=True,
        )
        with open(args.capture_stdout, "wb") as f:
            f.write(res.stdout)
        return 0

    return subprocess.call(cmd)


if __name__ == "__main__":
    sys.exit(main())