fix(spanner): enable toStruct support for structs with proto message pointer fields (#10704)

Co-authored-by: Jason Bradshaw <jason@j2ceb.com> Co-authored-by: rahul2393 <irahul@google.com>

Author: jmbradshaw79

spanner/value.go

@@ -1265,6 +1265,15 @@ func decodeValue(v *proto3.Value, t *sppb.Type, ptr interface{}, opts ...DecodeO
 acode = t.ArrayElementType.Code
 atypeAnnotation = t.ArrayElementType.TypeAnnotation
 }
+
+if code == sppb.TypeCode_PROTO && reflect.TypeOf(ptr).Elem().Kind() == reflect.Ptr {
+pve := reflect.ValueOf(ptr).Elem()
+if pve.IsNil() {
+pve.Set(reflect.New(pve.Type().Elem()))
+}
+ptr = pve.Interface()
+}
+
 _, isNull := v.Kind.(*proto3.Value_NullValue)
 
 // Do the decoding based on the type of ptr.

spanner/value_test.go

@@ -1982,6 +1982,14 @@ func TestDecodeValue(t *testing.T) {
 },
 {desc: "decode ENUM to protoreflect.Enum", proto: protoEnumProto(pb.Genre_ROCK), protoType: protoEnumType(protoEnumfqn), want: singerEnumValue},
 {desc: "decode PROTO to NullProto", proto: protoMessageProto(&singerProtoMsg), protoType: protoMessageType(protoMessagefqn), want: NullProtoMessage{&singerProtoMsg, true}},
+{desc: "decode PROTO to *pb.SingerInfo", proto: protoMessageProto(&singerProtoMsg), protoType: protoMessageType(protoMessagefqn),
+want: &pb.SingerInfo{
+SingerId: proto.Int64(1),
+BirthDate: proto.String("January"),
+Nationality: proto.String("Country1"),
+Genre: &singerEnumValue,
+},
+},
 {desc: "decode NULL to NullProto", proto: nullProto(), protoType: protoMessageType(protoMessagefqn), want: NullProtoMessage{}},
 {desc: "decode ENUM to NullEnum", proto: protoEnumProto(pb.Genre_ROCK), protoType: protoEnumType(protoEnumfqn), want: NullProtoEnum{&singerEnumValue, true}},
 {desc: "decode NULL to NullEnum", proto: nullProto(), protoType: protoEnumType(protoEnumfqn), want: NullProtoEnum{}},