fix: Raise an exception when left and right are the same

capellambse_context_diagrams/collectors/exchanges.py

@@ -163,6 +163,12 @@ def get_left_and_right(self) -> None:
             self.data.children.append(self.left)
             assert self.right is not None
             self.data.children.append(self.right)
+            if self.left == self.right:
+                raise errors.CycleError(
+                    "The interface is a cycle, connecting the same "
+                    "source and target."
+                )
+
         except AttributeError as error:
             logger.exception("Interface collection failed: \n%r", str(error))
 

capellambse_context_diagrams/errors.py

@@ -6,3 +6,7 @@
 
 class CapellambseError(Exception):
     """Error raised by capellambse."""
+
+
+class CycleError(CapellambseError):
+    """Error raised when a cycle is detected."""