scripts/_medvision_test_support.py

#!/usr/bin/env python3
"""Shared bootstrap for the standalone loader test scripts.

`MedVision.py` imports `datasets` at module scope, so any test that wants to
reach its module-level helpers has to satisfy that import first. The stub below
is a stdlib-only stand-in used only when the real library is absent — everything
under test is module-level and pure, so nothing stubbed here is ever executed;
the stub only has to let the module import and build its BUILDER_CONFIGS.

This lives in one place because both test scripts need it and the stub must
mirror `MedVision.py`'s `from datasets import (...)` list: with two copies, a new
symbol imported by the loader has to be added to both in lockstep or one suite
dies at import.

Not importable as a package — the test scripts are run as
`python scripts/<name>.py`, which puts `scripts/` on `sys.path[0]`, so a plain
`import _medvision_test_support` works.
"""
import importlib.util
import logging
import os
import sys
import tempfile
import types

_HERE = os.path.dirname(os.path.abspath(__file__))
MEDVISION_PY = os.path.join(_HERE, "..", "MedVision.py")
INFO_CSV = os.path.join(_HERE, "..", "info", "v1.3.0", "ConfigurationsList_All.csv")


def install_datasets_stub():
    """Register a minimal stdlib-only `datasets` in sys.modules."""
    m = types.ModuleType("datasets")

    class BuilderConfig:
        def __init__(self, name=None, version=None, **kw):
            self.name = name
            self.version = version
            for k, v in kw.items():
                setattr(self, k, v)

        def create_config_id(self, config_kwargs, custom_features=None):
            # Return the injected kwargs so tests can read the fingerprint token
            # directly instead of parsing a hashed id.
            return dict(config_kwargs or {})

    class GeneratorBasedBuilder:
        pass

    def _passthrough(*a, **k):
        return a[0] if len(a) == 1 else (a or k)

    m.BuilderConfig = BuilderConfig
    m.GeneratorBasedBuilder = GeneratorBasedBuilder
    m.Split = types.SimpleNamespace(TRAIN="train", TEST="test")
    m.SplitGenerator = _passthrough
    m.DatasetInfo = _passthrough
    m.Features = _passthrough
    m.Value = _passthrough
    m.Sequence = _passthrough
    m.logging = types.SimpleNamespace(get_logger=logging.getLogger)
    sys.modules["datasets"] = m


def load_loader(tmp_prefix="medvision_test_"):
    """Import MedVision.py and return the module.

    Points MedVision_DATA_DIR at a throwaway directory if unset — the loader
    raises at import time without it — and falls back to the stub when the real
    `datasets` is not installed.
    """
    os.environ.setdefault("MedVision_DATA_DIR", tempfile.mkdtemp(prefix=tmp_prefix))
    try:
        import datasets  # noqa: F401
    except ModuleNotFoundError:
        install_datasets_stub()
    spec = importlib.util.spec_from_file_location("medvision_loader", MEDVISION_PY)
    mod = importlib.util.module_from_spec(spec)
    spec.loader.exec_module(mod)
    return mod