edit_pset()'s unpack_unit_value() couldn't distinguish "no Unit dict was
passed" from "{"Unit": None, ...} passed to explicitly clear an existing
override" -- both collapsed to a bare None, and every consuming call site
checked truthiness, so there was no way to actually clear a previously-set
property Unit override once one existed. Fixed with a private _NO_UNIT
sentinel; bare (unwrapped) values still leave Unit untouched exactly as
before.
edit_qto() had no Unit-handling capability at all: neither
update_existing_property() nor add_new_properties() ever read or wrote a
quantity's Unit attribute. Added the same {"Unit": ..., "NominalValue": ...}
wrapped-dict convention edit_pset() already supports, disambiguated from
the pre-existing IfcPhysicalComplexQuantity dict convention
({"Discrimination": ..., "HasQuantities": ...}) by checking for a "Unit"
key -- a complex-quantity spec never contains one.
ifcopenshell.util.unit gains two small helpers:
- get_unit_scale(unit): dispatches to get_derived_unit_scale/
get_named_unit_scale depending on unit type, also used to de-duplicate
calculate_unit_scale()'s own inline dispatch of the same logic.
- get_candidate_units(ifc_file, unit_type): all units in a file matching a
given unit type, unlike get_project_unit()'s single-default lookup.
Adds regression tests for all of the above, including explicit-clear,
bare-value-preserves-override, and complex-quantity-routing-unaffected
cases.
Richard Brice