Enable serialization of non-GridQubits. (#2966)

* Enable serialization of non-GridQubits.

* Lint fixes for serializer.

* LineQubit proto IDs must be digits-only.

* Add coverage.

* named_qubit_* -> qubit_*

* Fix lint error.

Author: 95-martin-orion

cirq/google/api/v2/__init__.py

@@ -25,6 +25,7 @@
     grid_qubit_from_proto_id,
     line_qubit_from_proto_id,
     named_qubit_from_proto_id,
+    qubit_from_proto_id,
     qubit_to_proto_id,
 )
 

cirq/google/api/v2/program.py

@@ -41,6 +41,42 @@ def qubit_to_proto_id(q: 'cirq.Qid') -> str:
             type(q)))
 
 
+def qubit_from_proto_id(proto_id: str) -> 'cirq.Qid':
+    """Return a `cirq.Qid` for a proto id.
+
+    Proto IDs of the form {int}_{int} are parsed as GridQubits.
+
+    Proto IDs of the form {int} are parsed as LineQubits.
+
+    All other proto IDs are parsed as NamedQubits. Note that this will happily
+    accept any string; for circuits which explicitly use Grid or LineQubits,
+    prefer one of the specialized methods below.
+
+    Args:
+        proto_id: The id to convert.
+
+    Returns:
+        A `cirq.Qid` corresponding to the proto id.
+    """
+    num_coords = len(proto_id.split('_'))
+    if num_coords == 2:
+        try:
+            grid_q = grid_qubit_from_proto_id(proto_id)
+            return grid_q
+        except ValueError:
+            pass  # Not a grid qubit.
+    elif num_coords == 1:
+        try:
+            line_q = line_qubit_from_proto_id(proto_id)
+            return line_q
+        except ValueError:
+            pass  # Not a line qubit.
+
+    # named_qubit_from_proto has no failure condition.
+    named_q = named_qubit_from_proto_id(proto_id)
+    return named_q
+
+
 def grid_qubit_from_proto_id(proto_id: str) -> 'cirq.GridQubit':
     """Parse a proto id to a `cirq.GridQubit`.
 

cirq/google/api/v2/program_test.py

@@ -72,3 +72,17 @@ def test_line_qubit_from_proto_id_invalid():
 
 def test_named_qubit_from_proto_id():
     assert v2.named_qubit_from_proto_id('a') == cirq.NamedQubit('a')
+
+
+def test_generic_qubit_from_proto_id():
+    assert v2.qubit_from_proto_id('1_2') == cirq.GridQubit(1, 2)
+    assert v2.qubit_from_proto_id('1') == cirq.LineQubit(1)
+    assert v2.qubit_from_proto_id('a') == cirq.NamedQubit('a')
+
+    # Despite the fact that int(1_2_3) = 123, only pure numbers are parsed into
+    # LineQubits.
+    assert v2.qubit_from_proto_id('1_2_3') == cirq.NamedQubit('1_2_3')
+
+    # All non-int-parseable names are converted to NamedQubits.
+    assert v2.qubit_from_proto_id('a') == cirq.NamedQubit('a')
+    assert v2.qubit_from_proto_id('1_b') == cirq.NamedQubit('1_b')

cirq/google/op_deserializer.py

@@ -94,7 +94,7 @@ def from_proto(self,
                    *,
                    arg_function_language: str = '') -> 'cirq.Operation':
         """Turns a cirq.google.api.v2.Operation proto into a GateOperation."""
-        qubits = [v2.grid_qubit_from_proto_id(q.id) for q in proto.qubits]
+        qubits = [v2.qubit_from_proto_id(q.id) for q in proto.qubits]
         args = self._args_from_proto(
             proto, arg_function_language=arg_function_language)
         if self.num_qubits_param is not None:

cirq/google/op_serializer.py

@@ -13,12 +13,12 @@
 # limitations under the License.
 
 from dataclasses import dataclass
-from typing import (Callable, cast, List, Optional, Type, TypeVar, Union,
+from typing import (Callable, List, Optional, Type, TypeVar, Union,
                     TYPE_CHECKING)
 
 import numpy as np
 
-from cirq import devices, ops
+from cirq import ops
 from cirq.google.api import v2
 from cirq.google import arg_func_langs
 from cirq.google.arg_func_langs import _arg_to_proto
@@ -104,8 +104,6 @@ def to_proto(
     ) -> Optional[v2.program_pb2.Operation]:
         """Returns the cirq.google.api.v2.Operation message as a proto dict."""
 
-        if not all(isinstance(qubit, devices.GridQubit) for qubit in op.qubits):
-            raise ValueError('All qubits must be GridQubits')
         gate = op.gate
         if not isinstance(gate, self.gate_type):
             raise ValueError(
@@ -120,8 +118,7 @@ def to_proto(
 
         msg.gate.id = self.serialized_gate_id
         for qubit in op.qubits:
-            msg.qubits.add().id = v2.qubit_to_proto_id(
-                cast(devices.GridQubit, qubit))
+            msg.qubits.add().id = v2.qubit_to_proto_id(qubit)
         for arg in self.args:
             value = self._value_from_gate(op, arg)
             if value is not None:

cirq/google/op_serializer_test.py

@@ -258,7 +258,7 @@ def test_to_proto_unsupported_type():
         serializer.to_proto(GateWithProperty(b's')(q))
 
 
-def test_to_proto_unsupported_qubit_type():
+def test_to_proto_named_qubit_supported():
     serializer = cg.GateOpSerializer(gate_type=GateWithProperty,
                                      serialized_gate_id='my_gate',
                                      args=[
@@ -268,8 +268,56 @@ def test_to_proto_unsupported_qubit_type():
                                              op_getter='val')
                                      ])
     q = cirq.NamedQubit('a')
-    with pytest.raises(ValueError, match='GridQubit'):
-        serializer.to_proto(GateWithProperty(1.0)(q))
+    arg_value = 1.0
+    result = serializer.to_proto(GateWithProperty(arg_value)(q))
+
+    expected = op_proto({
+        'gate': {
+            'id': 'my_gate'
+        },
+        'args': {
+            'my_val': {
+                'arg_value': {
+                    'float_value': arg_value
+                }
+            }
+        },
+        'qubits': [{
+            'id': 'a'
+        }]
+    })
+    assert result == expected
+
+
+def test_to_proto_line_qubit_supported():
+    serializer = cg.GateOpSerializer(gate_type=GateWithProperty,
+                                     serialized_gate_id='my_gate',
+                                     args=[
+                                         cg.SerializingArg(
+                                             serialized_name='my_val',
+                                             serialized_type=float,
+                                             op_getter='val')
+                                     ])
+    q = cirq.LineQubit('10')
+    arg_value = 1.0
+    result = serializer.to_proto(GateWithProperty(arg_value)(q))
+
+    expected = op_proto({
+        'gate': {
+            'id': 'my_gate'
+        },
+        'args': {
+            'my_val': {
+                'arg_value': {
+                    'float_value': arg_value
+                }
+            }
+        },
+        'qubits': [{
+            'id': '10'
+        }]
+    })
+    assert result == expected
 
 
 def test_to_proto_required_but_not_present():