cost web ui:

- add "Linked rate" column,
- assign a cost rate to multiple cost items by selecting linked rate cells & clicking the "assign" button on the chosen cost rate
#5369

src/ifcopenshell-python/ifcopenshell/util/cost.py

@@ -307,6 +307,34 @@ def get_product_quantity_names(elements: list[ifcopenshell.entity_instance]) ->
     return [n for n in names if n != "id"]
 
 
+def get_cost_schedule(cost_item: ifcopenshell.entity_instance) -> ifcopenshell.entity_instance:
+    """Returns the cost schedule of a cost item.
+    """
+    for rel in cost_item.HasAssignments or []:
+        if rel.is_a("IfcRelAssignsToControl") and rel.RelatingControl.is_a("IfcCostSchedule"):
+            return rel.RelatingControl
+    for rel in cost_item.Nests or []:
+        return get_cost_schedule(rel.RelatingObject)
+
+
+def get_cost_rate(
+    file: ifcopenshell_wrapper.file, cost_item: ifcopenshell.entity_instance
+) -> Optional[ifcopenshell.entity_instance]:
+    """Returns the cost rate of a cost item.
+
+    """
+    # There is no direct relationship between a cost item and a cost rate in IFC, so we need to infer it, based on the assumption that cost_rate.CostValues == cost_item.CostValues.
+    if get_cost_schedule(cost_item).PredefinedType == "SCHEDULEOFRATES":
+        return None # Cost item is already a cost rate
+    if cost_item.CostValues:
+        potential_rates = file.get_inverse(cost_item.CostValues[0])
+        for potential_rate in potential_rates:
+            schedule = get_cost_schedule(potential_rate)
+            if schedule.PredefinedType == "SCHEDULEOFRATES":
+                return potential_rate
+    return None
+
+
 class CostValueUnserialiser:
     def parse(self, formula: str):
         l = lark.Lark(