Step 1: API Compatibility Check (MANDATORY before writing shims) (+2)

Step 1: API Compatibility Check (MANDATORY before writing shims)

# Compare __init__ signatures: old vs canonical
python3 -c "
import inspect
from old.module import OldClass
from canonical.module import CanonicalClass
print('OLD:', inspect.signature(OldClass.__init__))
print('NEW:', inspect.signature(CanonicalClass.__init__))
"

Checklist before shimming any class:

• __init__ kwarg signatures match (no removed/renamed parameters)
• Factory classmethods match (from_geojson(path) vs from_geojson(path, name))
• All module-level attributes that tests patch exist on canonical (HAS_RASTERIO, HAS_FOLIUM)

Step 2: Diverged API — Use Relative Imports, Do NOT Shim

If __init__ signatures differ between old and canonical:

• Do NOT shim the base class — any subclass calling super().__init__(crs=crs) with the old kwarg will crash at runtime with TypeError: unexpected keyword argument
• Fix the subclass: change its import to use a local relative import pointing to the compatible (old) class; shim only the unaffected modules (core/, io/, integrations/)

# WRONG: shim breaks subclass calling super().__init__(crs=crs)
# specialized/gis/layers/feature_layer.py (shim)
from digitalmodel.gis.layers.feature_layer import FeatureLayer  # canonical dropped crs kwarg

# CORRECT: keep old feature_layer.py as-is; fix the subclass import
# specialized/gis/layers/well_layer.py
from .feature_layer import FeatureLayer   # relative → uses local compatible class

Step 3: Re-export Patch-Target Attributes

Tests that use unittest.mock.patch.object(module, "HAS_X", ...) require HAS_X to exist as a module-level attribute on the shim module. Shims must re-export these flags:

# WRONG: shim omits the flag
from digitalmodel.gis.io.geotiff_handler import GeoTIFFHandler  # noqa: F401
# → patch.object(geotiff_handler, "HAS_RASTERIO", False) raises AttributeError

# CORRECT: re-export flag alongside the class
from digitalmodel.gis.io.geotiff_handler import GeoTIFFHandler, HAS_RASTERIO  # noqa: F401
__all__ = ['GeoTIFFHandler', 'HAS_RASTERIO']