fix fail of qobj run without run_options (Qiskit#1792)

* fix fail of qobj run without run_options

* fix lint error

---------

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

qiskit_aer/backends/aerbackend.py

@@ -186,8 +186,8 @@ def run(self, circuits, validate=False, parameter_binds=None, **run_options):
                 for key, value in circuits.config.__dict__.items():
                     if key not in run_options and value is not None:
                         run_options[key] = value
-                if "parameter_binds" in run_options:
-                    parameter_binds = run_options.pop("parameter_binds")
+            if "parameter_binds" in run_options:
+                parameter_binds = run_options.pop("parameter_binds")
             return self._run_qobj(circuits, validate, parameter_binds, **run_options)
 
         only_circuits = True

releasenotes/notes/fix_qobj_run-8ea657a93ce9acd2.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Aer still supports Qobj as an argument of :meth:`~.AerSimulator.run` though
+    it was deprecated. However, since 0.12.0, it always fails if no ``run_options``
+    is specified. This fix enables simulation of Qobj without ``run_options``.

test/terra/backends/aer_simulator/test_circuit.py

@@ -15,7 +15,7 @@
 from math import sqrt
 from ddt import ddt
 import numpy as np
-from qiskit import ClassicalRegister, QuantumCircuit, QuantumRegister
+from qiskit import ClassicalRegister, QuantumCircuit, QuantumRegister, assemble
 from qiskit.circuit import CircuitInstruction
 from test.terra.reference import ref_algorithms
 
@@ -173,6 +173,29 @@ def test_partial_result_a_single_invalid_circuit(self):
         self.assertTrue(hasattr(result.results[1].data, "counts"))
         self.assertFalse(hasattr(result.results[0].data, "counts"))
 
+    def test_run_qobj(self):
+        """Test qobj run"""
+
+        qubits = QuantumRegister(3)
+        clbits = ClassicalRegister(3)
+
+        circuit = QuantumCircuit(qubits, clbits)
+        circuit.h(qubits[0])
+        circuit.cx(qubits[0], qubits[1])
+        circuit.cx(qubits[0], qubits[2])
+
+        for q, c in zip(qubits, clbits):
+            circuit.measure(q, c)
+
+        backend = self.backend()
+
+        shots = 1000
+        with self.assertWarns(DeprecationWarning):
+            result = backend.run(assemble(circuit), shots=shots).result()
+
+        self.assertSuccess(result)
+        self.compare_counts(result, [circuit], [{"0x0": 500, "0x7": 500}], delta=0.05 * shots)
+
     def test_numpy_integer_shots(self):
         """Test implicit cast of shot option from np.int_ to int."""