fix(features): lazy package imports so one broken module can't sink the rest (#10)

src/features/__init__.py

@@ -3,30 +3,40 @@
 
 Provides comprehensive feature extraction for market regime detection
 and position sizing algorithms.
+
+Public names are imported lazily (PEP 562). A broken dependency in one
+module (for example base.py's data-layer import) therefore no longer
+prevents importing unrelated, self-contained modules in this package
+(greeks, pnl, position_models, ...).
 """
 
-from .base import FeatureEngineering
-from .regime_features import (
-    PriceStructureFeatures,
-    TrendIndicators,
-    MomentumIndicators,
-    VolatilityFeatures,
-    VolumeFeatures,
-    SupportResistanceFeatures,
-    MarketContextFeatures,
-    EventFeatures,
-    RegimeStateVector
-)
-
-__all__ = [
-    "FeatureEngineering",
-    "PriceStructureFeatures",
-    "TrendIndicators",
-    "MomentumIndicators",
-    "VolatilityFeatures",
-    "VolumeFeatures",
-    "SupportResistanceFeatures",
-    "MarketContextFeatures",
-    "EventFeatures",
-    "RegimeStateVector",
-]
+import importlib
+
+# Map each public name to the submodule that defines it.
+_EXPORTS = {
+    "FeatureEngineering": ".base",
+    "PriceStructureFeatures": ".regime_features",
+    "TrendIndicators": ".regime_features",
+    "MomentumIndicators": ".regime_features",
+    "VolatilityFeatures": ".regime_features",
+    "VolumeFeatures": ".regime_features",
+    "SupportResistanceFeatures": ".regime_features",
+    "MarketContextFeatures": ".regime_features",
+    "EventFeatures": ".regime_features",
+    "RegimeStateVector": ".regime_features",
+}
+
+__all__ = list(_EXPORTS)
+
+
+def __getattr__(name: str):
+    """Lazily import and return a public attribute (PEP 562)."""
+    module_name = _EXPORTS.get(name)
+    if module_name is None:
+        raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
+    module = importlib.import_module(module_name, __name__)
+    return getattr(module, name)
+
+
+def __dir__():
+    return sorted(__all__)

tests/features/test_lazy_init.py

@@ -0,0 +1,40 @@
+"""
+Regression tests for lazy feature-package imports (issue #10).
+
+The src.features package must not eagerly import its submodules, so a broken
+dependency in one module (e.g. base.py's data-layer import) cannot take down
+unrelated, self-contained modules in the package.
+"""
+
+import importlib
+import sys
+
+import pytest
+
+
+def _purge_features():
+    for name in list(sys.modules):
+        if name == "src.features" or name.startswith("src.features."):
+            del sys.modules[name]
+
+
+def test_importing_package_does_not_eagerly_load_base():
+    """Importing the package must not pull in base (its broken dependency)."""
+    _purge_features()
+    importlib.import_module("src.features")
+    assert "src.features.base" not in sys.modules
+
+
+def test_clean_submodule_imports_without_base():
+    """A self-contained submodule imports without requiring base."""
+    _purge_features()
+    importlib.import_module("src.features.position_models")
+    assert "src.features.base" not in sys.modules
+
+
+def test_unknown_attribute_raises():
+    """Accessing an undefined public name still raises AttributeError."""
+    _purge_features()
+    features = importlib.import_module("src.features")
+    with pytest.raises(AttributeError):
+        features.DefinitelyNotExported