Fix #1795. New support for conversion based units with offsets, like fahrenheit.

src/ifcopenshell-python/test/api/unit/test_add_conversion_based_unit.py

@@ -0,0 +1,43 @@
+import test.bootstrap
+import ifcopenshell.api
+
+
+class TestAddConversionBasedUnit(test.bootstrap.IFC4):
+    def test_run(self):
+        unit = ifcopenshell.api.run("unit.add_conversion_based_unit", self.file, name="foot")
+        assert unit.is_a("IfcConversionBasedUnit")
+        assert unit.Dimensions.LengthExponent == 1
+        assert unit.Dimensions.MassExponent == 0
+        assert unit.Dimensions.TimeExponent == 0
+        assert unit.Dimensions.ElectricCurrentExponent == 0
+        assert unit.Dimensions.ThermodynamicTemperatureExponent == 0
+        assert unit.Dimensions.AmountOfSubstanceExponent == 0
+        assert unit.Dimensions.LuminousIntensityExponent == 0
+        assert unit.UnitType == "LENGTHUNIT"
+        assert unit.Name == "foot"
+        assert unit.ConversionFactor.ValueComponent.wrappedValue == 0.3048
+        si_unit = unit.ConversionFactor.UnitComponent
+        assert si_unit.is_a("IfcSIUnit")
+        assert si_unit.UnitType == "LENGTHUNIT"
+        assert si_unit.Prefix is None
+        assert si_unit.Name == "METRE"
+
+    def test_adding_a_unit_with_offset(self):
+        unit = ifcopenshell.api.run("unit.add_conversion_based_unit", self.file, name="fahrenheit")
+        assert unit.is_a("IfcConversionBasedUnitWithOffset")
+        assert unit.Dimensions.LengthExponent == 0
+        assert unit.Dimensions.MassExponent == 0
+        assert unit.Dimensions.TimeExponent == 0
+        assert unit.Dimensions.ElectricCurrentExponent == 0
+        assert unit.Dimensions.ThermodynamicTemperatureExponent == 1
+        assert unit.Dimensions.AmountOfSubstanceExponent == 0
+        assert unit.Dimensions.LuminousIntensityExponent == 0
+        assert unit.UnitType == "THERMODYNAMICTEMPERATUREUNIT"
+        assert unit.Name == "fahrenheit"
+        assert unit.ConversionFactor.ValueComponent.wrappedValue == 1.8
+        si_unit = unit.ConversionFactor.UnitComponent
+        assert si_unit.is_a("IfcSIUnit")
+        assert si_unit.UnitType == "THERMODYNAMICTEMPERATUREUNIT"
+        assert si_unit.Prefix is None
+        assert si_unit.Name == "KELVIN"
+        assert unit.ConversionOffset == -459.67