Add Concat to cirq-google sweep proto (#6821)

* add Concat to sweeps

* json repr

* json testing

* add test for empty sweep

* comments

* coverage for keys property

* add concat

* compile proto

* compile proto

* fix test

* rm duplicate files

cirq-google/cirq_google/api/v2/run_context.proto

@@ -92,6 +92,15 @@ message SweepFunction {
     // the iterator will produce: {a: 1, b: 3} and {a: 2, b: 3}.
     // The shorter sweeps will be filled by repeating their last value.
     ZIP_LONGEST = 3;
+
+    // Concatenates multiple sweeps to a new sweep.
+    // All sweeps must share the same descriptors.
+    //
+    // Example of concat:
+    // If one sweep assigns 'a' to the values 0, 1, 2, and another sweep assigns
+    // 'a' to the values 3, 4, 5, the concatenation produces a sweep assigning
+    // 'a' to the values 0, 1, 2, 3, 4, 5 in sequence.
+    CONCAT = 4;
   }
 
   FunctionType function_type = 1;

cirq-google/cirq_google/api/v2/sweeps.py

@@ -81,6 +81,10 @@ def sweep_to_proto(
         out.sweep_function.function_type = run_context_pb2.SweepFunction.ZIP
         for s in sweep.sweeps:
             sweep_to_proto(s, out=out.sweep_function.sweeps.add())
+    elif isinstance(sweep, cirq.Concat):
+        out.sweep_function.function_type = run_context_pb2.SweepFunction.CONCAT
+        for s in sweep.sweeps:
+            sweep_to_proto(s, out=out.sweep_function.sweeps.add())
     elif isinstance(sweep, cirq.Linspace) and not isinstance(sweep.key, sympy.Expr):
         out.single_sweep.parameter_key = sweep.key
         out.single_sweep.linspace.first_point = sweep.start
@@ -135,6 +139,8 @@ def sweep_from_proto(msg: run_context_pb2.Sweep) -> cirq.Sweep:
             return cirq.Zip(*factors)
         if func_type == run_context_pb2.SweepFunction.ZIP_LONGEST:
             return cirq.ZipLongest(*factors)
+        if func_type == run_context_pb2.SweepFunction.CONCAT:
+            return cirq.Concat(*factors)
 
         raise ValueError(f'invalid sweep function type: {func_type}')
     if which == 'single_sweep':

cirq-google/cirq_google/api/v2/sweeps_test.py

@@ -80,6 +80,7 @@ def _values(self) -> Iterator[float]:
             cirq.Points('a', [1]) * cirq.Points('b', [1.0])
             + cirq.Points('c', ["abc"]) * cirq.Points("d", [1, 2, 3, 4])  # type: ignore[list-item]
         ),
+        cirq.Concat(cirq.Points('a', [1.0, 2.0, 3.0]), cirq.Points('a', [4.0])),
     ],
 )
 def test_sweep_to_proto_roundtrip(sweep):