build.py

#!/usr/bin/env python3
import os
import sys
import subprocess
from pathlib import Path

def main():
    if len(sys.argv) < 2:
        print(f"Usage: {sys.argv[0]} <pxr_install_dir>", file=sys.stderr)
        sys.exit(1)

    pxr_dir = sys.argv[1]
    conda_prefix = os.environ.get("CONDA_PREFIX", "")
    build_dir = Path("build")
    build_dir.mkdir(exist_ok=True)

    cmake_args = [
        "cmake", "..",
        "-G", "Ninja",
        "-DCMAKE_BUILD_TYPE=Debug",
        f"-DCMAKE_PREFIX_PATH={conda_prefix};{pxr_dir}",
        f"-DCPLUS_INCLUDE_PATH={conda_prefix}/include/",
        f"-DUSD_INSTALL_DIR={pxr_dir}",
    ]
    # conda-forge clang on macOS uses a target-triple prefix, which Qt's cmake
    # config mistakes for cross-compilation. Tell Qt the host Qt == target Qt.
    if sys.platform == "darwin" and conda_prefix:
        cmake_args += [f"-DQT_HOST_PATH={conda_prefix}"]

    subprocess.run(cmake_args, cwd=build_dir, check=True)

    subprocess.run(["cmake", "--build", "."], cwd=build_dir, check=True)

    # Generate env.py — cross-platform environment setup script
    env_py = build_dir / "usdsim_env.py"
    conda_lib = str(Path(conda_prefix) / "lib") if conda_prefix else ""
    pxr_lib = str(Path(pxr_dir) / "lib")
    pxr_python = str(Path(pxr_dir) / "lib" / "python")
    build_lib = str(build_dir.resolve() / "lib")

    conda_python = str(Path(conda_prefix) / "bin" / "python3") if conda_prefix else ""
    qt_plugin_path = str(Path(conda_prefix) / "lib" / "qt6" / "plugins") if conda_prefix else ""
    qml_import_path = str(Path(conda_prefix) / "lib" / "qt6" / "qml") if conda_prefix else ""

    env_py.write_text('''\
#!/usr/bin/env python3
"""Auto-generated by build.py.

Usage:
  1. As a launcher:  python build/env.py  your_script.py [args...]
  2. As an import:    import env   (with build/ on sys.path or PYTHONPATH)

On Linux/macOS, the dynamic library path must be set before the process loads
shared libs, so this module re-execs the current process with the correct env.
"""
import os, sys

_PATHS = ''' + repr([build_lib, pxr_python]) + '''
_LD_PATHS = ''' + repr([p for p in [conda_lib, pxr_lib, build_lib] if p]) + '''
_CONDA_PYTHON = ''' + repr(conda_python) + '''
_QT_PLUGIN_PATH = ''' + repr(qt_plugin_path) + '''
_QML_IMPORT_PATH = ''' + repr(qml_import_path) + '''

# 0. Set Qt environment variables if needed
if _QT_PLUGIN_PATH and os.path.isdir(_QT_PLUGIN_PATH):
    os.environ.setdefault("QT_PLUGIN_PATH", _QT_PLUGIN_PATH)
if _QML_IMPORT_PATH and os.path.isdir(_QML_IMPORT_PATH):
    os.environ.setdefault("QML2_IMPORT_PATH", _QML_IMPORT_PATH)
_FONTCONFIG_PATH = os.path.join(os.path.dirname(_QT_PLUGIN_PATH), '..', 'etc', 'fonts') if _QT_PLUGIN_PATH else ''
if _FONTCONFIG_PATH and os.path.isdir(_FONTCONFIG_PATH):
    os.environ.setdefault("FONTCONFIG_PATH", _FONTCONFIG_PATH)

# 0b. Re-exec with the build-time Python if running a different interpreter
if _CONDA_PYTHON and os.path.exists(_CONDA_PYTHON) and os.path.realpath(sys.executable) != os.path.realpath(_CONDA_PYTHON):
    os.execv(_CONDA_PYTHON, [_CONDA_PYTHON] + sys.argv)

# 1. Fix sys.path
for p in reversed(_PATHS):
    if p not in sys.path:
        sys.path.insert(0, p)

# 2. Fix dynamic library path — re-exec if not already set
if sys.platform == "win32":
    for p in _LD_PATHS:
        os.add_dll_directory(p)
else:
    _lib_var = "DYLD_LIBRARY_PATH" if sys.platform == "darwin" else "LD_LIBRARY_PATH"
    _ld = os.environ.get(_lib_var, "")
    _missing = [p for p in _LD_PATHS if p not in _ld]
    if _missing:
        os.environ[_lib_var] = os.pathsep.join(
            _LD_PATHS + ([_ld] if _ld else [])
        )
        os.execv(sys.executable, [sys.executable] + sys.argv)

# 3. If run as a script, exec the target
if __name__ == "__main__":
    if len(sys.argv) < 2:
        print("Usage: python build/env.py <script.py> [args...]")
        sys.exit(1)
    script = sys.argv[1]
    sys.argv = sys.argv[1:]  # shift so script sees correct argv
    with open(script) as f:
        code = compile(f.read(), script, "exec")
    exec(code, {"__name__": "__main__", "__file__": os.path.abspath(script)})
''')
    env_py.chmod(0o755)
    print(f"Generated {env_py}")

if __name__ == "__main__":
    main()