qbz/scripts/qt-cargo.py

#!/usr/bin/env python3
"""Run Cargo with the *native* Qt SDK included in cc-rs's cache inputs.

Cargo does not discover changes to system C++ headers. In particular, an
in-place Qt update can leave cxx-qt-lib built with old inline templates while
qbz-qt uses new ones. The linker coalesces their identically named symbols;
this caused the QList<float> startup SIGSEGV on 2026-09-06.

Use this entry point for Qt builds/tests, including direct Cargo invocations:
  python3 scripts/qt-cargo.py build --release --manifest-path crates/Cargo.toml -p qbz-qt

No target cleanup, profile changes, or RUSTFLAGS: a content-derived, unused
C++ define invalidates cc-rs consumers when the SDK changes, in either profile
and with any Rust toolchain. Existing CXXFLAGS (including MSVC flags) survive.
"""

import hashlib
import os
from pathlib import Path
import re
import shutil
import subprocess
import sys


def query(qmake, name):
    return subprocess.check_output(
        [qmake, "-query", name], text=True, stderr=subprocess.PIPE, timeout=15
    ).strip()


def find_qmake(env):
    explicit = env.get("QMAKE")
    candidates = [explicit] if explicit else ["qmake6", "qmake"]
    for candidate in candidates:
        executable = shutil.which(candidate, path=env.get("PATH"))
        if executable:
            version = query(executable, "QT_VERSION")
            if re.fullmatch(r"6\.\d+\.\d+(?:[-+].*)?", version):
                # Keep argv[0]: qmake may be a qtchooser symlink.
                return os.path.abspath(executable), version
    raise RuntimeError("Qt 6 qmake not found; set QMAKE to the intended SDK's qmake")


def header_files(root, modules_only=False):
    # Homebrew SDKs can expose headers through directory symlinks. Follow
    # them, but visit each real directory once so a cyclic link cannot hang.
    seen = set()
    for directory, dirs, files in os.walk(root, followlinks=True, onerror=raise_error):
        if modules_only and Path(directory) == root:
            # Homebrew can report /opt/homebrew/include, not a Qt-only root.
            dirs[:] = [name for name in dirs if name.startswith("Qt")]
            files = [name for name in files if name.startswith("Qt")]
        real = Path(directory).resolve()
        if real in seen:
            dirs[:] = []
            continue
        seen.add(real)
        dirs.sort()
        for name in sorted(files):
            yield Path(directory) / name


def raise_error(error):
    raise error


def sdk_fingerprint(qmake, version):
    headers = Path(query(qmake, "QT_INSTALL_HEADERS"))
    libraries = Path(query(qmake, "QT_INSTALL_LIBS"))
    digest = hashlib.sha256()
    # Paths are intentional: switching SDK roots must also rebuild native
    # archives and their recorded linker search paths.
    for value in ("qbz-qt-sdk-v1", qmake, version, str(headers.resolve()),
                  str(libraries)):
        digest.update(value.encode() + b"\0")
    count = 0
    def sdk_headers():
        if headers.is_dir():
            for path in header_files(headers, modules_only=True):
                yield str(path.relative_to(headers)), path
        # cxx-qt-build also consumes these. Homebrew's qmake may point at a
        # shared include root with NO QtCore subdir; its real headers live in
        # QT_INSTALL_LIBS/QtCore.framework/Headers instead.
        for framework in sorted(libraries.glob("Qt*.framework")):
            root = framework / "Headers"
            if root.is_dir():
                for path in header_files(root):
                    yield f"frameworks/{framework.name}/Headers/{path.relative_to(root)}", path

    for name, path in sdk_headers():
        digest.update(name.encode() + b"\0")
        content = path.read_bytes()
        digest.update(len(content).to_bytes(8, "big"))
        digest.update(content)
        count += 1
    if not count:
        raise RuntimeError(f"Qt headers are missing or empty: {headers}, {libraries}")
    return digest.hexdigest()[:32]


def cargo_environment(env):
    result = dict(env)
    qmake, version = find_qmake(result)
    fingerprint = sdk_fingerprint(qmake, version)
    # cc-rs tracks and appends CXXFLAGS even with target-specific flags.
    # Remove only our own previous marker, making nested invocations stable.
    flags = re.sub(r"(?:^|\s)-DQBZ_QT_SDK_[0-9a-f]{32}=1(?=\s|$)", "",
                   result.get("CXXFLAGS", "")).strip()
    result["CXXFLAGS"] = f"{flags} -DQBZ_QT_SDK_{fingerprint}=1".strip()
    result["QMAKE"] = qmake
    return result, version, fingerprint


def main():
    if len(sys.argv) < 2:
        raise RuntimeError("usage: qt-cargo.py <cargo subcommand> [arguments...]")
    env, version, fingerprint = cargo_environment(os.environ)
    print(f"[qt-cargo] Qt {version}, SDK {fingerprint}, qmake={env['QMAKE']}",
          file=sys.stderr, flush=True)
    os.execvpe("cargo", ["cargo", *sys.argv[1:]], env)


if __name__ == "__main__":
    try:
        main()
    except (OSError, RuntimeError, subprocess.SubprocessError) as error:
        print(f"[qt-cargo] {error}", file=sys.stderr)
        sys.exit(1)