Fix #3121. Merge equivalent contexts when merging projects in MergeProject Ifcpatch recipe.

src/ifcpatch/ifcpatch/recipes/MergeProject.py

@@ -46,10 +46,46 @@ class Patcher:
 
     def patch(self):
         source = ifcopenshell.open(self.filepath)
+        self.existing_contexts = self.file.by_type("IfcGeometricRepresentationContext")
+        self.added_contexts = set()
         original_project = self.file.by_type("IfcProject")[0]
         merged_project = self.file.add(source.by_type("IfcProject")[0])
+        for element in source.by_type("IfcGeometricRepresentationContext"):
+            new = self.file.add(element)
+            self.added_contexts.add(new)
         for element in source:
             self.file.add(element)
         for inverse in self.file.get_inverse(merged_project):
             ifcopenshell.util.element.replace_attribute(inverse, merged_project, original_project)
         self.file.remove(merged_project)
+        self.reuse_existing_contexts()
+
+    def reuse_existing_contexts(self):
+        to_delete = set()
+
+        for added_context in self.added_contexts:
+            equivalent_existing_context = self.get_equivalent_existing_context(added_context)
+            if equivalent_existing_context:
+                for inverse in self.file.get_inverse(added_context):
+                    ifcopenshell.util.element.replace_attribute(inverse, added_context, equivalent_existing_context)
+                to_delete.add(added_context)
+
+        for added_context in to_delete:
+            ifcopenshell.util.element.remove_deep2(self.file, added_context)
+
+    def get_equivalent_existing_context(self, added_context):
+        for context in self.existing_contexts:
+            if context.is_a() != added_context.is_a():
+                continue
+            if context.is_a("IfcGeometricRepresentationSubContext"):
+                if (
+                    context.ContextType == added_context.ContextType
+                    and context.ContextIdentifier == added_context.ContextIdentifier
+                    and context.TargetView == added_context.TargetView
+                ):
+                    return context
+            elif (
+                context.ContextType == added_context.ContextType
+                and context.ContextIdentifier == added_context.ContextIdentifier
+            ):
+                return context