Adds the IFC-library primitives the ifcpatch Migrate recipe needs for a
defensive IFC4 / IFC4X3 -> IFC2X3 downgrade without each caller
reinventing the wheel.
In ifcopenshell.util.schema:
- Migrator(fallback_element_to_proxy=False) opt-in: when True, IFC4-only
IfcElement subclasses (IfcLamp, IfcPipeSegment, IfcGeographicElement,
...) migrate to IfcBuildingElementProxy instead of raising. Default
preserves the strict failure-on-unmappable contract for existing
callers (classification API, etc.).
- geometry_classes_introduced_after(target, source) derives the
IfcRepresentationItem subclasses present in `source` but absent in
`target` directly from the loaded schemas. Cached per pair. Replaces
hand-curated class lists that drift with each IFC update.
ifc4_only_geometry_classes() retained as an alias.
- generate_default_value synthesises a unit IfcAxis2Placement2D /
IfcAxis2Placement3D when downgrading entities whose Position became
required in the target schema (IfcIShapeProfileDef and friends in
IFC2X3).
- Enum-mismatch detection upgraded from string-matched RuntimeError to a
structural check via ifcopenshell.util.attribute.get_enum_items so
upgrade paths still surface real bugs loudly.
In ifcopenshell.util.shape_builder:
- polygonal_face_set_to_faceted_brep converts IfcPolygonalFaceSet /
IfcTriangulatedFaceSet (IFC4-only) directly to IfcFacetedBrep,
preserving topology including IfcIndexedPolygonalFaceWithVoids inner
bounds. Validates inputs at the boundary.
- arc_to_polyline_points approximates a circular arc through three
points with a chord polyline of configurable subdivisions. Tolerates
floating-point noise on planar Z. Raises on non-planar or invalid
inputs.
Test coverage: 47 unit tests across schema + shape_builder lanes
covering each helper directly (no transitive-only coverage), including
regression pins for the IFC4X3-prefix ordering invariant in
get_fallback_schema and the strict-default Migrator contract.
Generated with the assistance of an AI coding tool.
Gorgious56