Avoid duplicate inputs with fanout

b_asic/signal_flow_graph.py

@@ -565,7 +565,7 @@ class SFG(AbstractOperation):
     @property
     def operations(self) -> List[Operation]:
         """Get all operations of this graph in depth-first order."""
-        return self._operations_dfs_order
+        return list(self._operations_dfs_order)
 
     def find_by_type_name(
         self, type_name: TypeName
@@ -1137,7 +1137,8 @@ class SFG(AbstractOperation):
                         self._components_dfs_order.extend(
                             [new_signal, source.operation]
                         )
-                        self._operations_dfs_order.append(source.operation)
+                        if not source.operation in self._operations_dfs_order:
+                            self._operations_dfs_order.append(source.operation)
 
                     # Check if the signal has not been added before.
                     elif (

test/test_operation.py

@@ -156,7 +156,7 @@ class TestToSfg:
 
         assert but1.evaluate(1, 1)[0] == but1_sfg.evaluate(1, 1)[0]
         assert but1.evaluate(1, 1)[1] == but1_sfg.evaluate(1, 1)[1]
-        assert len(but1_sfg.operations) == 8
+        assert len(but1_sfg.operations) == 6
 
     def test_add_to_sfg(self):
         add1 = Addition()

test/test_sfg.py

@@ -24,6 +24,7 @@ from b_asic.core_operations import (
     SymmetricTwoportAdaptor,
 )
 from b_asic.save_load_structure import python_to_sfg, sfg_to_python
+from b_asic.special_operations import Delay
 
 
 class TestInit:
@@ -1563,6 +1564,27 @@ class TestSFGErrors:
             sfg.inputs_required_for_output(1)
 
 
+class TestInputDuplicationBug:
+    def test_input_is_not_duplicated_in_operation_list(self):
+        # Inputs:
+        in1 = Input(name="in1")
+        out1 = Output(name="out1")
+
+        # Operations:
+        t1 = Delay(initial_value=0, name="")
+        t1.inputs[0].connect(in1)
+        add1 = t1 + in1
+
+        out1.inputs[0].connect(add1)
+
+        twotapfir = SFG(inputs=[in1], outputs=[out1], name='twotapfir')
+
+        assert (
+            len([op for op in twotapfir.operations if isinstance(op, Input)])
+            == 1
+        )
+
+
 class TestCriticalPath:
     def test_single_accumulator(self, sfg_simple_accumulator: SFG):
         sfg_simple_accumulator.set_latency_of_type(Addition.type_name(), 5)