ModelCache crashes on construction in environments without a resolvable home director

[sainath-seelam]

Description:

Constructing SSolutionsRepositoryBuilder() raises RuntimeError: Could not determine home directory. in any environment where the user's home directory cannot be resolved, because ModelCache.__init__ eagerly calls Path.home() regardless of whether caching will actually be used.

Traceback

File "SSolutionsRepositoryBuilder.py", line 34, in __init__
    self._cache = ModelCache()
File "ModelCache.py", line 34, in __init__
    self._dir = cache_dir or self._default_dir()
File "ModelCache.py", line 26, in _default_dir
    d = Path.home() / ".mps_cli_cache"
File "pathlib.py", line 1406, in expanduser
    raise RuntimeError("Could not determine home directory.")

Expected Behaviour and Fix:

ModelCache.__init__ eagerly calls Path.home() to resolve the default cache directory at construction time, before any file is ever read or written. In environments where HOME (Linux/macOS) or USERPROFILE (Windows) is unset, Path.home() raises RuntimeError: Could not determine home directory. — crashing the entire program on startup.

The fix is to defer _default_dir() out of __init__ and call it lazily the first time load() or save() is actually used:

def __init__(self, cache_dir: Path | None = None):
    self._dir = cache_dir  # None = resolve on first access

def _get_dir(self) -> Path:
    if self._dir is None:
        self._dir = self._default_dir()
    return self._dir

def load(self, path: Path):
    try:
        cache_file = self._get_dir() / self._key(path)
        ...

def save(self, path: Path, model) -> None:
    try:
        cache_file = self._get_dir() / self._key(path)
        ...

This way constructing ModelCache() or SSolutionsRepositoryBuilder() is always safe, and Path.home() is only called if caching is actually exercised.

[Prithvi686]

This issue has been fixed and released as part of mps-cli-py 0.6.1 version.