Deprecate loose custom basis gates in preset pm pipieline

qiskit/transpiler/preset_passmanagers/generate_preset_pass_manager.py

@@ -17,7 +17,13 @@
 import copy
 import warnings
 
-from qiskit.circuit.controlflow import CONTROL_FLOW_OP_NAMES
+from qiskit.circuit.controlflow import (
+    CONTROL_FLOW_OP_NAMES,
+    IfElseOp,
+    WhileLoopOp,
+    ForLoopOp,
+    SwitchCaseOp,
+)
 from qiskit.circuit.library.standard_gates import get_standard_gate_name_mapping
 from qiskit.circuit.quantumregister import Qubit
 from qiskit.providers.backend import Backend
@@ -312,6 +318,7 @@ def generate_preset_pass_manager(
     _skip_target = (
         target is None
         and backend is None
+        # Note: instruction_durations is deprecated and will be removed in 2.0 (no need for alternative)
         and (basis_gates is None or coupling_map is None or instruction_durations is not None)
     )
 
@@ -336,23 +343,31 @@ def generate_preset_pass_manager(
             # Only parse backend properties when the target isn't skipped to
             # preserve the former behavior of transpile.
             backend_properties = _parse_backend_properties(backend_properties, backend)
-            # Build target from constraints.
-            target = Target.from_configuration(
-                basis_gates=basis_gates,
-                num_qubits=backend.num_qubits if backend is not None else None,
-                coupling_map=coupling_map,
-                # If the instruction map has custom gates, do not give as config, the information
-                # will be added to the target with update_from_instruction_schedule_map
-                inst_map=inst_map if inst_map and not inst_map.has_custom_gate() else None,
-                backend_properties=backend_properties,
-                instruction_durations=instruction_durations,
-                concurrent_measurements=(
-                    backend.target.concurrent_measurements if backend is not None else None
-                ),
-                dt=dt,
-                timing_constraints=timing_constraints,
-                custom_name_mapping=name_mapping,
-            )
+            with warnings.catch_warnings():
+                # TODO: inst_map will be removed in 2.0
+                warnings.filterwarnings(
+                    "ignore",
+                    category=DeprecationWarning,
+                    message=".*``inst_map`` is deprecated as of Qiskit 1.3.*",
+                    module="qiskit",
+                )
+                # Build target from constraints.
+                target = Target.from_configuration(
+                    basis_gates=basis_gates,
+                    num_qubits=backend.num_qubits if backend is not None else None,
+                    coupling_map=coupling_map,
+                    # If the instruction map has custom gates, do not give as config, the information
+                    # will be added to the target with update_from_instruction_schedule_map
+                    inst_map=inst_map if inst_map and not inst_map.has_custom_gate() else None,
+                    backend_properties=backend_properties,
+                    instruction_durations=instruction_durations,
+                    concurrent_measurements=(
+                        backend.target.concurrent_measurements if backend is not None else None
+                    ),
+                    dt=dt,
+                    timing_constraints=timing_constraints,
+                    custom_name_mapping=name_mapping,
+                )
 
     # Update target with custom gate information. Note that this is an exception to the priority
     # order (target > loose constraints), added to handle custom gates for scheduling passes.
@@ -433,9 +448,14 @@ def generate_preset_pass_manager(
 def _parse_basis_gates(basis_gates, backend, inst_map, skip_target):
     name_mapping = {}
     standard_gates = get_standard_gate_name_mapping()
-    # Add control flow gates by default to basis set
+    # Add control flow gates by default to basis set and name mapping
     default_gates = {"measure", "delay", "reset"}.union(CONTROL_FLOW_OP_NAMES)
-
+    name_mapping = {
+        "if_else": IfElseOp,
+        "while_loop": WhileLoopOp,
+        "for_loop": ForLoopOp,
+        "switch_case": SwitchCaseOp,
+    }
     try:
         instructions = set(basis_gates)
         for name in default_gates:
@@ -450,7 +470,15 @@ def _parse_basis_gates(basis_gates, backend, inst_map, skip_target):
             return None, name_mapping, skip_target
 
         for inst in instructions:
-            if inst not in standard_gates or inst not in default_gates:
+            if inst not in standard_gates and inst not in default_gates:
+                warnings.warn(
+                    category=DeprecationWarning,
+                    message="Providing custom gates through the ``basis_gates`` argument is deprecated "
+                    "for both ``transpile`` and ``generate_preset_pass_manager`` as of Qiskit 1.3.0. "
+                    "It will be removed in Qiskit 2.0. The ``target`` parameter should be used instead. "
+                    "You can build a target instance using ``Target.from_configuration()`` and provide"
+                    "custom gate definitions with the ``custom_name_mapping`` argument.",
+                )
                 skip_target = True
                 break
 
@@ -463,7 +491,18 @@ def _parse_basis_gates(basis_gates, backend, inst_map, skip_target):
 
     # Check for custom instructions before removing calibrations
     for inst in instructions:
-        if inst not in standard_gates or inst not in default_gates:
+        if inst not in standard_gates and inst not in default_gates:
+            if inst not in backend.operation_names:
+                # do not raise warning when the custom instruction comes from the backend
+                # (common case with BasicSimulator)
+                warnings.warn(
+                    category=DeprecationWarning,
+                    message="Providing custom gates through the ``basis_gates`` argument is deprecated "
+                    "for both ``transpile`` and ``generate_preset_pass_manager`` as of Qiskit 1.3.0. "
+                    "It will be removed in Qiskit 2.0. The ``target`` parameter should be used instead. "
+                    "You can build a target instance using ``Target.from_configuration()`` and provide"
+                    "custom gate definitions with the ``custom_name_mapping`` argument.",
+                )
             skip_target = True
             break
 

releasenotes/notes/deprecate-custom-basis-gates-transpile-e4b5893377f23acb.yaml

@@ -0,0 +1,18 @@
+---
+deprecations_transpiler:
+  - |
+    Providing custom gates through the ``basis_gates`` argument is deprecated 
+    for both :func:`.transpile` and :func:`generate_preset_pass_manager`, this functionality
+    will be removed in Qiskit 2.0. Custom gates are still supported in the :class:`.Target` model,
+    and can be provided through the ``target`` argument. One can build a :class:`.Target` instance
+    from scratch or use the :meth:`.Target.from_configuration` method with the ``custom_name_mapping`` 
+    argument. For example::
+
+        from qiskit.circuit.library import XGate
+        from qiskit.transpiler.target import Target
+
+        basis_gates = ["my_x", "cx"]
+        custom_name_mapping = {"my_x": XGate()}
+        target = Target.from_configuration(
+            basis_gates=basis_gates, num_qubits=2, custom_name_mapping=custom_name_mapping
+        )

test/python/transpiler/test_preset_passmanagers.py

@@ -1735,3 +1735,40 @@ def test_unsupported_targets_raise(self, optimization_level):
             pass
         with self.assertRaisesRegex(TranspilerError, "The control-flow construct.*not supported"):
             transpile(qc, target=target, optimization_level=optimization_level)
+
+    @data(0, 1, 2, 3)
+    def test_custom_basis_gates_raise(self, optimization_level):
+        """Test that trying to provide a list of custom basis gates to generate_preset_pass_manager
+        raises a deprecation warning."""
+
+        with self.subTest(msg="no warning"):
+            # check that the warning isn't raised if the basis gates aren't custom
+            basis_gates = ["x", "cx"]
+            _ = generate_preset_pass_manager(
+                optimization_level=optimization_level, basis_gates=basis_gates
+            )
+
+        with self.subTest(msg="warning only basis gates"):
+            # check that the warning is raised if they are custom
+            basis_gates = ["my_gate"]
+            with self.assertWarnsRegex(
+                DeprecationWarning,
+                "Providing custom gates through the ``basis_gates`` argument is deprecated",
+            ):
+                _ = generate_preset_pass_manager(
+                    optimization_level=optimization_level, basis_gates=basis_gates
+                )
+
+        with self.subTest(msg="no warning custom basis gates in backend"):
+            # check that the warning is not raised if a loose custom gate is found in the backend
+            backend = GenericBackendV2(num_qubits=2)
+            gate = Gate(name="my_gate", num_qubits=1, params=[])
+            backend.target.add_instruction(gate)
+            self.assertEqual(
+                backend.operation_names,
+                ["cx", "id", "rz", "sx", "x", "reset", "delay", "measure", "my_gate"],
+            )
+            basis_gates = ["my_gate"]
+            _ = generate_preset_pass_manager(
+                optimization_level=optimization_level, basis_gates=basis_gates, backend=backend
+            )