Function _load_introspect_tests_cache

ci/meson/test_discovery.py:22–55

Load cached test names from disk if the cache is still valid. The cache is stored in `` /.meson_introspect_tests_cache.json`` as a plain JSON array of test name strings (NOT the full meson introspect output). Storing only names keeps the file small (~6 KB vs ~180 KB),

(build_dir: Path)

def _load_introspect_tests_cache(build_dir: Path) -> list[str] | None:
    """
    Load cached test names from disk if the cache is still valid.

    The cache is stored in ``<build_dir>/.meson_introspect_tests_cache.json``
    as a plain JSON array of test name strings (NOT the full meson introspect
    output).  Storing only names keeps the file small (~6 KB vs ~180 KB),
    reducing parse time from ~100 ms to ~5 ms.

    The cache is considered valid when its mtime is at least as recent as
    ``<build_dir>/build.ninja``.  build.ninja is rewritten whenever meson
    reconfigures (adding or removing tests), so its mtime is a reliable
    invalidation signal for the registered test list.

    Returns:
        List of registered test name strings on cache hit, or None on miss/error.
    """
    cache_path = build_dir / ".meson_introspect_tests_cache.json"
    build_ninja = build_dir / "build.ninja"
    if not cache_path.exists() or not build_ninja.exists():
        return None
    try:
        cache_mtime = cache_path.stat().st_mtime
        ninja_mtime = build_ninja.stat().st_mtime
        if cache_mtime < ninja_mtime:
            return None  # build.ninja is newer → cache is stale
        data = json.loads(cache_path.read_text(encoding="utf-8"))
        # Validate: must be a list of strings (names-only format)
        if isinstance(data, list) and (not data or isinstance(data[0], str)):
            return data
        # Stale full-dict format from a previous version → treat as miss
        return None
    except (OSError, json.JSONDecodeError):
        return None


def _save_introspect_tests_cache(build_dir: Path, test_names: list[str]) -> None: