Add client-side validations

qiskit_ibm_runtime/estimator.py

@@ -35,7 +35,7 @@
 from .utils.deprecation import deprecate_arguments, issue_deprecation_msg
 from .utils.qctrl import validate as qctrl_validate
 from .utils.qctrl import validate_v2 as qctrl_validate_v2
-
+from .utils.validations import validate_estimator_pubs
 
 # pylint: disable=unused-import,cyclic-import
 from .session import Session
@@ -184,6 +184,7 @@ def run(
 
         """
         coerced_pubs = [EstimatorPub.coerce(pub, precision) for pub in pubs]
+        validate_estimator_pubs(coerced_pubs)
         return self._run(coerced_pubs)  # type: ignore[arg-type]
 
     def _validate_options(self, options: dict) -> None:

qiskit_ibm_runtime/sampler.py

@@ -16,7 +16,6 @@
 import os
 from typing import Dict, Optional, Sequence, Any, Union, Iterable
 import logging
-import warnings
 
 from qiskit.circuit import QuantumCircuit
 from qiskit.primitives import BaseSampler
@@ -36,6 +35,7 @@
 from .utils.deprecation import deprecate_arguments, issue_deprecation_msg
 from .utils.qctrl import validate as qctrl_validate
 from .utils.qctrl import validate_v2 as qctrl_validate_v2
+from .utils.validations import validate_classical_registers
 from .options import SamplerOptions
 
 logger = logging.getLogger(__name__)
@@ -146,12 +146,7 @@ def run(self, pubs: Iterable[SamplerPubLike], *, shots: int | None = None) -> Ru
         """
         coerced_pubs = [SamplerPub.coerce(pub, shots) for pub in pubs]
 
-        if any(len(pub.circuit.cregs) == 0 for pub in coerced_pubs):
-            warnings.warn(
-                "One of your circuits has no output classical registers and so the result "
-                "will be empty. Did you mean to add measurement instructions?",
-                UserWarning,
-            )
+        validate_classical_registers(coerced_pubs)
 
         return self._run(coerced_pubs)  # type: ignore[arg-type]
 

qiskit_ibm_runtime/utils/validations.py

@@ -0,0 +1,72 @@
+# This code is part of Qiskit.
+#
+# (C) Copyright IBM 2024.
+#
+# This code is licensed under the Apache License, Version 2.0. You may
+# obtain a copy of this license in the LICENSE.txt file in the root directory
+# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
+#
+# Any modifications or derivative works of this code must retain this
+# copyright notice, and modified files need to carry a notice indicating
+# that they have been altered from the originals.
+
+"""Utilities for data validation."""
+from typing import List
+import warnings
+import keyword
+from qiskit.primitives.containers.sampler_pub import SamplerPub
+from qiskit.primitives.containers.estimator_pub import EstimatorPub
+
+
+def validate_classical_registers(pubs: List[SamplerPub]) -> None:
+    """Validates the classical registers in the pub won't cause problems that can be caught client-side.
+
+    Args:
+        pubs: The list of pubs to validate
+
+    Raises:
+        ValueError: If any circuit has a size-0 creg.
+        ValueError: If any circuit has a creg whose name is not a valid identifier.
+        ValueError: If any circuit has a creg whose name is a Python keyword.
+    """
+
+    for index, pub in enumerate(pubs):
+        if len(pub.circuit.cregs) == 0:
+            warnings.warn(
+                f"The {index}-th circuit has no output classical registers so the result "
+                "will be empty. Did you mean to add measurement instructions?",
+                UserWarning,
+            )
+
+        for reg in pub.circuit.cregs:
+            # size 0 classical register will crash the server-side sampler
+            if reg.size == 0:
+                raise ValueError(
+                    f"Classical register {reg.name} is of size 0, which is not allowed"
+                )
+            if not reg.name.isidentifier():
+                raise ValueError(
+                    f"Classical register names must be valid identifiers, but {reg.name} "
+                    f"is not. Valid identifiers contain only alphanumeric letters "
+                    f"(a-z and A-Z), decimal digits (0-9), or underscores (_)"
+                )
+            if keyword.iskeyword(reg.name):
+                raise ValueError(
+                    f"Classical register names cannot be Python keywords, but {reg.name} "
+                    f"is such a keyword. You can see the Python keyword list here: "
+                    f"https://docs.python.org/3/reference/lexical_analysis.html#keywords"
+                )
+
+
+def validate_estimator_pubs(pubs: List[EstimatorPub]) -> None:
+    """Validates the estimator pubs won't cause problems that can be caught client-side.
+
+    Args:
+        pubs: The list of pubs to validate
+
+    Raises:
+        ValueError: If any observable array is of size 0
+    """
+    for pub in pubs:
+        if pub.observables.shape == (0,):
+            raise ValueError("Empty observables array is not allowed")

test/unit/test_estimator.py

@@ -277,3 +277,12 @@ def test_unsupported_dynamical_decoupling_with_dynamic_circuits(self):
             "Dynamical decoupling currently cannot be used with dynamic circuits",
         ):
             inst.run(in_pubs)
+
+    def test_estimator_validations(self):
+        """Test exceptions when failing client-side validations."""
+        backend = get_mocked_backend()
+        inst = EstimatorV2(backend=backend)
+        circ = QuantumCircuit(2)
+        obs = []
+        with self.assertRaisesRegex(ValueError, "Empty observables array is not allowed"):
+            inst.run(pubs=[(circ, obs)])

test/unit/test_sampler.py

@@ -17,7 +17,7 @@
 from ddt import data, ddt, named_data
 import numpy as np
 
-from qiskit import QuantumCircuit, transpile
+from qiskit import QuantumCircuit, transpile, QuantumRegister, ClassicalRegister
 from qiskit.primitives.containers.sampler_pub import SamplerPub
 from qiskit.circuit.library import RealAmplitudes
 from qiskit_ibm_runtime import Sampler, Session, SamplerV2, SamplerOptions, IBMInputValueError
@@ -152,6 +152,31 @@ def test_run_default_options(self):
                     f"{inputs} and {expected} not partially equal.",
                 )
 
+    def test_sampler_validations(self):
+        """Test exceptions when failing client-side validations."""
+        with Session(
+            service=FakeRuntimeService(channel="ibm_quantum", token="abc"),
+            backend="common_backend",
+        ) as session:
+            inst = SamplerV2(session=session)
+            circ = QuantumCircuit(QuantumRegister(2), ClassicalRegister(0))
+            with self.assertRaisesRegex(ValueError, "Classical register .* is of size 0"):
+                inst.run([(circ,)])
+
+            creg = ClassicalRegister(2, "not-an-identifier")
+            circ = QuantumCircuit(QuantumRegister(2), creg)
+            with self.assertRaisesRegex(
+                ValueError, "Classical register names must be valid identifiers"
+            ):
+                inst.run([(circ,)])
+
+            creg = ClassicalRegister(2, "lambda")
+            circ = QuantumCircuit(QuantumRegister(2), creg)
+            with self.assertRaisesRegex(
+                ValueError, "Classical register names cannot be Python keywords"
+            ):
+                inst.run([(circ,)])
+
     def test_run_dynamic_circuit_with_fractional_opted(self):
         """Fractional opted backend cannot run dynamic circuits."""
         model_backend = FakeFractionalBackend()