Move "cirq_type" responsibility to protocols (#4704)

Fixes #4698.

This enforces the `'cirq_type': [<namespace>.]<classname>` convention for JSON serialization by assigning the "cirq_type" field in our protocols instead of in each class. Any external users who define a "cirq_type" will see a warning about this; after a deprecation cycle, we will begin raising errors to prevent explicit definition of "cirq_type" in classes.

cirq-core/cirq/circuits/circuit_operation.py

@@ -329,7 +329,6 @@ def __hash__(self):
 
     def _json_dict_(self):
         return {
-            'cirq_type': 'CircuitOperation',
             'circuit': self.circuit,
             'repetitions': self.repetitions,
             # JSON requires mappings to have keys of basic types.

cirq-core/cirq/circuits/circuit_operation_test.py

@@ -484,7 +484,6 @@ def test_json_dict():
     )
 
     assert op._json_dict_() == {
-        'cirq_type': 'CircuitOperation',
         'circuit': circuit,
         'repetitions': 1,
         'qubit_map': sorted([(k, v) for k, v in op.qubit_map.items()]),

cirq-core/cirq/circuits/circuit_test.py

@@ -4212,7 +4212,6 @@ def test_json_dict(circuit_cls):
     if circuit_cls == cirq.FrozenCircuit:
         moments = tuple(moments)
     assert c._json_dict_() == {
-        'cirq_type': circuit_cls.__name__,
         'moments': moments,
         'device': cirq.UNCONSTRAINED_DEVICE,
     }

cirq-core/cirq/devices/device.py

@@ -164,7 +164,6 @@ def __repr__(self):
     def _json_dict_(self):
         return {
             'qids': sorted(self.qids),
-            'cirq_type': self.__class__.__name__,
         }
 
     @classmethod

cirq-core/cirq/devices/grid_qubit_test.py

@@ -321,13 +321,11 @@ def test_neg():
 
 def test_to_json():
     assert cirq.GridQubit(5, 6)._json_dict_() == {
-        'cirq_type': 'GridQubit',
         'row': 5,
         'col': 6,
     }
 
     assert cirq.GridQid(5, 6, dimension=3)._json_dict_() == {
-        'cirq_type': 'GridQid',
         'row': 5,
         'col': 6,
         'dimension': 3,

cirq-core/cirq/devices/line_qubit_test.py

@@ -214,11 +214,9 @@ def test_neg():
 
 def test_json_dict():
     assert cirq.LineQubit(5)._json_dict_() == {
-        'cirq_type': 'LineQubit',
         'x': 5,
     }
     assert cirq.LineQid(5, 3)._json_dict_() == {
-        'cirq_type': 'LineQid',
         'x': 5,
         'dimension': 3,
     }

cirq-core/cirq/devices/named_topologies.py

@@ -13,7 +13,6 @@
 # limitations under the License.
 
 import abc
-import dataclasses
 import warnings
 from dataclasses import dataclass
 from typing import Dict, List, Tuple, Any, Sequence, Union, Iterable, TYPE_CHECKING
@@ -23,16 +22,12 @@
 
 from cirq import _compat
 from cirq.devices import GridQubit, LineQubit
-from cirq.protocols.json_serialization import obj_to_dict_helper
+from cirq.protocols.json_serialization import dataclass_json_dict
 
 if TYPE_CHECKING:
     import cirq
 
 
-def dataclass_json_dict(obj: Any, namespace: str = None) -> Dict[str, Any]:
-    return obj_to_dict_helper(obj, [f.name for f in dataclasses.fields(obj)], namespace=namespace)
-
-
 class NamedTopology(metaclass=abc.ABCMeta):
     """A topology (graph) with a name.
 

cirq-core/cirq/experiments/cross_entropy_benchmarking.py

@@ -253,7 +253,6 @@ class CrossEntropyResultDict(Mapping[Tuple['cirq.Qid', ...], CrossEntropyResult]
 
     def _json_dict_(self) -> Dict[str, Any]:
         return {
-            'cirq_type': self.__class__.__name__,
             'results': list(self.results.items()),
         }
 

cirq-core/cirq/experiments/single_qubit_readout_calibration.py

@@ -45,7 +45,6 @@ class SingleQubitReadoutCalibrationResult:
 
     def _json_dict_(self) -> Dict[str, Any]:
         return {
-            'cirq_type': self.__class__.__name__,
             'zero_state_errors': list(self.zero_state_errors.items()),
             'one_state_errors': list(self.one_state_errors.items()),
             'repetitions': self.repetitions,

cirq-core/cirq/ops/boolean_hamiltonian.py

@@ -94,7 +94,6 @@ def _value_equality_values_(self):
 
     def _json_dict_(self) -> Dict[str, Any]:
         return {
-            'cirq_type': self.__class__.__name__,
             'qubit_map': self._qubit_map,
             'boolean_strs': self._boolean_strs,
             'theta': self._theta,

cirq-core/cirq/ops/clifford_gate.py

@@ -488,7 +488,6 @@ def _from_json_dict_(cls, n, rs, xs, zs, **kwargs):
 
     def _json_dict_(self) -> Dict[str, Any]:
         json_dict = self._clifford_tableau._json_dict_()
-        json_dict['cirq_type'] = self.__class__.__name__
         return json_dict
 
     def _circuit_diagram_info_(

cirq-core/cirq/ops/common_gates.py

@@ -318,7 +318,6 @@ def __repr__(self) -> str:
 
     def _json_dict_(self) -> Dict[str, Any]:
         return {
-            'cirq_type': self.__class__.__name__,
             'rads': self._rads,
         }
 
@@ -539,7 +538,6 @@ def __repr__(self) -> str:
 
     def _json_dict_(self) -> Dict[str, Any]:
         return {
-            'cirq_type': self.__class__.__name__,
             'rads': self._rads,
         }
 
@@ -825,7 +823,6 @@ def __repr__(self) -> str:
 
     def _json_dict_(self) -> Dict[str, Any]:
         return {
-            'cirq_type': self.__class__.__name__,
             'rads': self._rads,
         }
 

cirq-core/cirq/ops/controlled_gate.py

@@ -260,7 +260,6 @@ def __repr__(self) -> str:
 
     def _json_dict_(self) -> Dict[str, Any]:
         return {
-            'cirq_type': self.__class__.__name__,
             'control_values': self.control_values,
             'control_qid_shape': self.control_qid_shape,
             'sub_gate': self.sub_gate,

cirq-core/cirq/ops/controlled_operation.py

@@ -254,7 +254,6 @@ def get_symbol(vals):
 
     def _json_dict_(self) -> Dict[str, Any]:
         return {
-            'cirq_type': self.__class__.__name__,
             'controls': self.controls,
             'control_values': self.control_values,
             'sub_operation': self.sub_operation,

cirq-core/cirq/ops/fourier_transform.py

@@ -42,7 +42,6 @@ def __init__(self, num_qubits: int, *, without_reverse: bool = False):
 
     def _json_dict_(self) -> Dict[str, Any]:
         return {
-            'cirq_type': self.__class__.__name__,
             'num_qubits': self._num_qubits,
             'without_reverse': self._without_reverse,
         }
@@ -98,7 +97,6 @@ def __init__(self, *, num_qubits: int, exponent: Union[float, sympy.Basic]):
 
     def _json_dict_(self) -> Dict[str, Any]:
         return {
-            'cirq_type': self.__class__.__name__,
             'num_qubits': self._num_qubits,
             'exponent': self.exponent,
         }

cirq-core/cirq/ops/fsim_gate_test.py

@@ -278,7 +278,6 @@ def test_fsim_repr():
 
 def test_fsim_json_dict():
     assert cirq.FSimGate(theta=0.123, phi=0.456)._json_dict_() == {
-        'cirq_type': 'FSimGate',
         'theta': 0.123,
         'phi': 0.456,
     }
@@ -799,7 +798,6 @@ def test_phased_fsim_json_dict():
     assert cirq.PhasedFSimGate(
         theta=0.12, zeta=0.34, chi=0.56, gamma=0.78, phi=0.9
     )._json_dict_() == {
-        'cirq_type': 'PhasedFSimGate',
         'theta': 0.12,
         'zeta': 0.34,
         'chi': 0.56,

cirq-core/cirq/ops/global_phase_op_test.py

@@ -268,6 +268,5 @@ def test_diagram():
 
 def test_global_phase_op_json_dict():
     assert cirq.GlobalPhaseOperation(-1j)._json_dict_() == {
-        'cirq_type': 'GlobalPhaseOperation',
         'coefficient': -1j,
     }

cirq-core/cirq/ops/identity.py

@@ -115,7 +115,6 @@ def _json_dict_(self) -> Dict[str, Any]:
         if not all(d == 2 for d in self._qid_shape):
             other['qid_shape'] = self._qid_shape
         return {
-            'cirq_type': self.__class__.__name__,
             'num_qubits': len(self._qid_shape),
             **other,
         }

cirq-core/cirq/ops/linear_combinations.py

@@ -783,7 +783,6 @@ def _json_dict_(self) -> Dict[str, Any]:
             key = [[k, v] for k, v in dict(projector_dict).items()]
             linear_dict.append([key, scalar])
         return {
-            'cirq_type': self.__class__.__name__,
             'linear_dict': linear_dict,
         }
 

cirq-core/cirq/ops/matrix_gates.py

@@ -84,7 +84,6 @@ def __init__(
 
     def _json_dict_(self) -> Dict[str, Any]:
         return {
-            'cirq_type': self.__class__.__name__,
             'matrix': self._matrix.tolist(),
             'qid_shape': self._qid_shape,
         }

cirq-core/cirq/ops/measurement_gate.py

@@ -229,7 +229,6 @@ def _json_dict_(self) -> Dict[str, Any]:
         if not all(d == 2 for d in self._qid_shape):
             other['qid_shape'] = self._qid_shape
         return {
-            'cirq_type': self.__class__.__name__,
             'num_qubits': len(self._qid_shape),
             'key': self.key,
             'invert_mask': self.invert_mask,

cirq-core/cirq/ops/moment_test.py

@@ -374,7 +374,7 @@ def test_json_dict():
     a = cirq.NamedQubit('a')
     b = cirq.NamedQubit('b')
     mom = cirq.Moment([cirq.CZ(a, b)])
-    assert mom._json_dict_() == {'cirq_type': 'Moment', 'operations': (cirq.CZ(a, b),)}
+    assert mom._json_dict_() == {'operations': (cirq.CZ(a, b),)}
 
 
 def test_inverse():

cirq-core/cirq/ops/named_qubit_test.py

@@ -136,12 +136,10 @@ def test_named_qid_range():
 
 def test_to_json():
     assert cirq.NamedQubit('c')._json_dict_() == {
-        'cirq_type': 'NamedQubit',
         'name': 'c',
     }
 
     assert cirq.NamedQid('c', dimension=3)._json_dict_() == {
-        'cirq_type': 'NamedQid',
         'name': 'c',
         'dimension': 3,
     }

cirq-core/cirq/ops/pauli_measurement_gate.py

@@ -149,7 +149,6 @@ def _value_equality_values_(self) -> Any:
 
     def _json_dict_(self) -> Dict[str, Any]:
         return {
-            'cirq_type': self.__class__.__name__,
             'observable': self._observable,
             'key': self.key,
         }

cirq-core/cirq/ops/pauli_string.py

@@ -177,7 +177,6 @@ def _value_equality_values_(self):
 
     def _json_dict_(self) -> Dict[str, Any]:
         return {
-            'cirq_type': self.__class__.__name__,
             # JSON requires mappings to have string keys.
             'qubit_pauli_map': list(self._qubit_pauli_map.items()),
             'coefficient': self.coefficient,
@@ -1294,7 +1293,6 @@ def inplace_left_multiply_by(
 
     def _json_dict_(self) -> Dict[str, Any]:
         return {
-            'cirq_type': self.__class__.__name__,
             # JSON requires mappings to have string keys.
             'pauli_int_dict': list(self.pauli_int_dict.items()),
             'coefficient': self.coefficient,

cirq-core/cirq/ops/permutation_gate_test.py

@@ -71,7 +71,6 @@ def test_permutation_gate_diagram():
 
 def test_permutation_gate_json_dict():
     assert cirq.QubitPermutationGate([0, 1, 2])._json_dict_() == {
-        'cirq_type': 'QubitPermutationGate',
         'permutation': (0, 1, 2),
     }
 

cirq-core/cirq/ops/phased_iswap_gate.py

@@ -76,7 +76,6 @@ def _num_qubits_(self) -> int:
 
     def _json_dict_(self) -> Dict[str, Any]:
         return {
-            'cirq_type': self.__class__.__name__,
             'phase_exponent': self._phase_exponent,
             'exponent': self._exponent,
         }

cirq-core/cirq/ops/projector.py

@@ -148,7 +148,6 @@ def __repr__(self) -> str:
 
     def _json_dict_(self) -> Dict[str, Any]:
         return {
-            'cirq_type': self.__class__.__name__,
             'projector_dict': list(self._projector_dict.items()),
             'coefficient': self._coefficient,
         }

cirq-core/cirq/ops/raw_types_test.py

@@ -73,7 +73,6 @@ def test_wrapped_qid():
     assert str(ValidQubit('a').with_dimension(3)) == 'TQ_a (d=3)'
 
     assert ValidQubit('zz').with_dimension(3)._json_dict_() == {
-        'cirq_type': '_QubitAsQid',
         'qubit': ValidQubit('zz'),
         'dimension': 3,
     }
@@ -370,9 +369,7 @@ def _qid_shape_(self):
 
 def test_gate_json_dict():
     g = cirq.CSWAP  # not an eigen gate (which has its own _json_dict_)
-    assert g._json_dict_() == {
-        'cirq_type': 'CSwapGate',
-    }
+    assert g._json_dict_() == {}
 
 
 def test_inverse_composite_diagram_info():

cirq-core/cirq/ops/state_preparation_channel.py

@@ -60,7 +60,6 @@ def _has_unitary_(self) -> bool:
     def _json_dict_(self) -> Dict[str, Any]:
         """Converts the gate object into a serializable dictionary"""
         return {
-            'cirq_type': self.__class__.__name__,
             'target_state': self._state.tolist(),
             'name': self._name,
         }

cirq-core/cirq/ops/tags.py

@@ -33,4 +33,4 @@ def __repr__(self) -> str:
         return 'cirq.VirtualTag()'
 
     def _json_dict_(self) -> Dict[str, str]:
-        return {'cirq_type': self.__class__.__name__}
+        return {}