Better initial_layout validation

qiskit/transpiler/passes/layout/full_ancilla_allocation.py

@@ -66,6 +66,7 @@ def run(self, dag):
             raise TranspilerError('FullAncillaAllocation pass requires property_set["layout"].')
 
         if layout:
+            FullAncillaAllocation.validate_layout(layout.get_registers(), set(dag.qregs.values()))
             layout_physical_qubits = list(range(max(layout.get_physical_bits()) + 1))
         else:
             layout_physical_qubits = []
@@ -90,3 +91,13 @@ def run(self, dag):
             self.property_set['layout'][idle_q] = qreg[idx]
 
         return dag
+
+    @staticmethod
+    def validate_layout(layout_qregs, dag_qregs):
+        """
+        Checks if all the qregs in layout_qregs already exist in dag_qregs. Otherwise, raise.
+        """
+        for qreg in layout_qregs:
+            if qreg not in dag_qregs:
+                raise TranspilerError('FullAncillaAllocation: The layout refers to a quantum '
+                                      'register that does not exist in circuit.')

qiskit/transpiler/passes/layout/set_layout.py

@@ -41,5 +41,5 @@ def run(self, dag):
         Returns:
             DAGCircuit: the original DAG.
         """
-        self.property_set['layout'] = self.layout
+        self.property_set['layout'] = None if self.layout is None else self.layout.copy()
         return dag

test/python/compiler/test_transpiler.py

@@ -30,7 +30,6 @@
 from qiskit.circuit import Parameter, Gate
 from qiskit.compiler import transpile
 from qiskit.converters import circuit_to_dag
-from qiskit.dagcircuit.exceptions import DAGCircuitError
 from qiskit.circuit.library import CXGate, U3Gate, U2Gate, U1Gate, RXGate, RYGate
 from qiskit.test import QiskitTestCase, Path
 from qiskit.test.mock import FakeMelbourne, FakeRueschlikon, FakeAlmaden
@@ -423,8 +422,11 @@ def test_wrong_initial_layout(self):
                               QuantumRegister(3, 'q')[1],
                               QuantumRegister(3, 'q')[2]]
 
-        self.assertRaises(DAGCircuitError, transpile,
-                          qc, backend, initial_layout=bad_initial_layout)
+        with self.assertRaises(TranspilerError) as cm:
+            transpile(qc, backend, initial_layout=bad_initial_layout)
+
+        self.assertEqual("FullAncillaAllocation: The layout refers to a quantum register that does "
+                         "not exist in circuit.", cm.exception.message)
 
     def test_parameterized_circuit_for_simulator(self):
         """Verify that a parameterized circuit can be transpiled for a simulator backend."""

test/python/transpiler/test_full_ancilla_allocation.py

@@ -19,6 +19,7 @@
 from qiskit.transpiler import CouplingMap, Layout
 from qiskit.transpiler.passes import FullAncillaAllocation
 from qiskit.test import QiskitTestCase
+from qiskit.transpiler.exceptions import TranspilerError
 
 
 class TestFullAncillaAllocation(QiskitTestCase):
@@ -146,6 +147,26 @@ def test_name_collision(self):
         self.assertEqual(len(other_reg), 2)
         self.assertRegex(other_reg.name, r'^ancilla\d+$')
 
+    def test_bad_layout(self):
+        """Layout referes to a register that do not exist in the circuit
+        """
+        qr = QuantumRegister(3, 'q')
+        circ = QuantumCircuit(qr)
+        dag = circuit_to_dag(circ)
+
+        initial_layout = Layout()
+        initial_layout[0] = QuantumRegister(4, 'q')[0]
+        initial_layout[1] = QuantumRegister(4, 'q')[1]
+        initial_layout[2] = QuantumRegister(4, 'q')[2]
+
+        pass_ = FullAncillaAllocation(self.cmap5)
+        pass_.property_set['layout'] = initial_layout
+
+        with self.assertRaises(TranspilerError) as cm:
+            pass_.run(dag)
+        self.assertEqual("FullAncillaAllocation: The layout refers to a quantum register that does "
+                         "not exist in circuit.", cm.exception.message)
+
 
 if __name__ == '__main__':
     unittest.main()