Fix handling of BackendV1 simulators in PassManagerConfig.from_backend (backport #9719)

qiskit/transpiler/instruction_durations.py

@@ -74,15 +74,17 @@ def from_backend(cls, backend: Backend):
         """
         # All durations in seconds in gate_length
         instruction_durations = []
-        for gate, insts in backend.properties()._gates.items():
-            for qubits, props in insts.items():
-                if "gate_length" in props:
-                    gate_length = props["gate_length"][0]  # Throw away datetime at index 1
-                    instruction_durations.append((gate, qubits, gate_length, "s"))
-        for q, props in backend.properties()._qubits.items():
-            if "readout_length" in props:
-                readout_length = props["readout_length"][0]  # Throw away datetime at index 1
-                instruction_durations.append(("measure", [q], readout_length, "s"))
+        backend_properties = backend.properties()
+        if hasattr(backend_properties, "_gates"):
+            for gate, insts in backend_properties._gates.items():
+                for qubits, props in insts.items():
+                    if "gate_length" in props:
+                        gate_length = props["gate_length"][0]  # Throw away datetime at index 1
+                        instruction_durations.append((gate, qubits, gate_length, "s"))
+            for q, props in backend.properties()._qubits.items():
+                if "readout_length" in props:
+                    readout_length = props["readout_length"][0]  # Throw away datetime at index 1
+                    instruction_durations.append(("measure", [q], readout_length, "s"))
 
         try:
             dt = backend.configuration().dt

qiskit/transpiler/passmanager_config.py

@@ -136,7 +136,9 @@ def from_backend(cls, backend, **pass_manager_options):
         if res.inst_map is None:
             if backend_version < 2:
                 if hasattr(backend, "defaults"):
-                    res.inst_map = backend.defaults().instruction_schedule_map
+                    defaults = backend.defaults()
+                    if defaults is not None:
+                        res.inst_map = defaults.instruction_schedule_map
             else:
                 res.inst_map = backend.instruction_schedule_map
         if res.coupling_map is None:

releasenotes/notes/fix-backendv1-pm-config-from-backend-914869dd6e1c06be.yaml

@@ -0,0 +1,9 @@
+---
+fixes:
+  - |
+    Fixed an issue with the :meth:`.PassManagerConfig.from_backend`
+    constructor method when it was used with a :class:`~.BackendV1` based
+    simulator backend. For some simulator backends which did not populate
+    some optional fields the constructor would error.
+    Fixed `#9265 <https://github.com/Qiskit/qiskit-terra/issues/9265>`__ and
+    `#8546 <https://github.com/Qiskit/qiskit-terra/issues/8546>`__

test/python/transpiler/test_passmanager_config.py

@@ -16,6 +16,7 @@
 from qiskit.providers.backend import Backend
 from qiskit.test import QiskitTestCase
 from qiskit.providers.fake_provider import FakeMelbourne, FakeArmonk, FakeHanoi, FakeHanoiV2
+from qiskit.providers.basicaer import QasmSimulatorPy
 from qiskit.transpiler.coupling import CouplingMap
 from qiskit.transpiler.passmanager_config import PassManagerConfig
 
@@ -71,6 +72,21 @@ def test_from_backend_and_user(self):
         )
         self.assertEqual(config.initial_layout, initial_layout)
 
+    def test_from_backendv1_inst_map_is_none(self):
+        """Test that from_backend() works with backend that has defaults defined as None."""
+        backend = FakeHanoi()
+        backend.defaults = lambda: None
+        config = PassManagerConfig.from_backend(backend)
+        self.assertIsInstance(config, PassManagerConfig)
+        self.assertIsNone(config.inst_map)
+
+    def test_simulator_backend_v1(self):
+        """Test that from_backend() works with backendv1 simulator."""
+        backend = QasmSimulatorPy()
+        config = PassManagerConfig.from_backend(backend)
+        self.assertIsInstance(config, PassManagerConfig)
+        self.assertIsNone(config.inst_map)
+
     def test_invalid_user_option(self):
         """Test from_backend() with an invalid user option."""
         with self.assertRaises(TypeError):