[wpimath] Improve C++ SimpleMotorFeedforward unit type support (#7440)

Allow using non-base types
Allow using angles for serde

wpimath/src/main/native/include/frc/controller/SimpleMotorFeedforward.h

@@ -20,8 +20,7 @@ namespace frc {
  * permanent-magnet DC motor.
  */
 template <class Distance>
-  requires std::same_as<units::meter, Distance> ||
-           std::same_as<units::radian, Distance>
+  requires units::length_unit<Distance> || units::angle_unit<Distance>
 class SimpleMotorFeedforward {
  public:
   using Velocity =

wpimath/src/main/native/include/frc/controller/proto/SimpleMotorFeedforwardProto.h

@@ -12,10 +12,12 @@
 #include "wpimath/protobuf/controller.npb.h"
 
 // Everything is converted into units for
-// frc::SimpleMotorFeedforward<units::meters>
+// frc::SimpleMotorFeedforward<units::meters> or
+// frc::SimpleMotorFeedforward<units::radians>
 
 template <class Distance>
-struct wpi::Protobuf<frc::SimpleMotorFeedforward<Distance>> {  // NOLINT
+  requires units::length_unit<Distance> || units::angle_unit<Distance>
+struct wpi::Protobuf<frc::SimpleMotorFeedforward<Distance>> {
   using MessageStruct = wpi_proto_ProtobufSimpleMotorFeedforward;
   using InputStream =
       wpi::ProtoInputStream<frc::SimpleMotorFeedforward<Distance>>;
@@ -24,6 +26,9 @@ struct wpi::Protobuf<frc::SimpleMotorFeedforward<Distance>> {  // NOLINT
 
   static std::optional<frc::SimpleMotorFeedforward<Distance>> Unpack(
       InputStream& stream) {
+    using BaseUnit =
+        units::unit<std::ratio<1>, units::traits::base_unit_of<Distance>>;
+    using BaseFeedforward = frc::SimpleMotorFeedforward<BaseUnit>;
     wpi_proto_ProtobufSimpleMotorFeedforward msg;
     if (!stream.Decode(msg)) {
       return {};
@@ -31,26 +36,23 @@ struct wpi::Protobuf<frc::SimpleMotorFeedforward<Distance>> {  // NOLINT
 
     return frc::SimpleMotorFeedforward<Distance>{
         units::volt_t{msg.ks},
-        units::unit_t<frc::SimpleMotorFeedforward<units::meters>::kv_unit>{
-            msg.kv},
-        units::unit_t<frc::SimpleMotorFeedforward<units::meters>::ka_unit>{
-            msg.ka},
+        units::unit_t<typename BaseFeedforward::kv_unit>{msg.kv},
+        units::unit_t<typename BaseFeedforward::ka_unit>{msg.ka},
         units::second_t{msg.dt},
     };
   }
 
   static bool Pack(OutputStream& stream,
                    const frc::SimpleMotorFeedforward<Distance>& value) {
+    using BaseUnit =
+        units::unit<std::ratio<1>, units::traits::base_unit_of<Distance>>;
+    using BaseFeedforward = frc::SimpleMotorFeedforward<BaseUnit>;
     wpi_proto_ProtobufSimpleMotorFeedforward msg{
         .ks = value.GetKs().value(),
-        .kv =
-            units::unit_t<frc::SimpleMotorFeedforward<units::meters>::kv_unit>{
-                value.GetKv()}
-                .value(),
-        .ka =
-            units::unit_t<frc::SimpleMotorFeedforward<units::meters>::ka_unit>{
-                value.GetKa()}
-                .value(),
+        .kv = units::unit_t<typename BaseFeedforward::kv_unit>{value.GetKv()}
+                  .value(),
+        .ka = units::unit_t<typename BaseFeedforward::ka_unit>{value.GetKa()}
+                  .value(),
         .dt = units::second_t{value.GetDt()}.value(),
     };
     return stream.Encode(msg);

wpimath/src/main/native/include/frc/controller/struct/SimpleMotorFeedforwardStruct.h

@@ -14,6 +14,7 @@
 // frc::SimpleMotorFeedforward<units::radians>
 
 template <class Distance>
+  requires units::length_unit<Distance> || units::angle_unit<Distance>
 struct wpi::Struct<frc::SimpleMotorFeedforward<Distance>> {
   static constexpr std::string_view GetTypeName() {
     return "SimpleMotorFeedforward";
@@ -25,40 +26,44 @@ struct wpi::Struct<frc::SimpleMotorFeedforward<Distance>> {
 
   static frc::SimpleMotorFeedforward<Distance> Unpack(
       std::span<const uint8_t> data) {
+    using BaseUnit =
+        units::unit<std::ratio<1>, units::traits::base_unit_of<Distance>>;
+    using BaseFeedforward = frc::SimpleMotorFeedforward<BaseUnit>;
     constexpr size_t kKsOff = 0;
     constexpr size_t kKvOff = kKsOff + 8;
     constexpr size_t kKaOff = kKvOff + 8;
     constexpr size_t kDtOff = kKaOff + 8;
     return {units::volt_t{wpi::UnpackStruct<double, kKsOff>(data)},
-            units::unit_t<frc::SimpleMotorFeedforward<units::meters>::kv_unit>{
+            units::unit_t<typename BaseFeedforward::kv_unit>{
                 wpi::UnpackStruct<double, kKvOff>(data)},
-            units::unit_t<frc::SimpleMotorFeedforward<units::meters>::ka_unit>{
+            units::unit_t<typename BaseFeedforward::ka_unit>{
                 wpi::UnpackStruct<double, kKaOff>(data)},
             units::second_t{wpi::UnpackStruct<double, kDtOff>(data)}};
   }
 
   static void Pack(std::span<uint8_t> data,
                    const frc::SimpleMotorFeedforward<Distance>& value) {
+    using BaseUnit =
+        units::unit<std::ratio<1>, units::traits::base_unit_of<Distance>>;
+    using BaseFeedforward = frc::SimpleMotorFeedforward<BaseUnit>;
     constexpr size_t kKsOff = 0;
     constexpr size_t kKvOff = kKsOff + 8;
     constexpr size_t kKaOff = kKvOff + 8;
     constexpr size_t kDtOff = kKaOff + 8;
     wpi::PackStruct<kKsOff>(data, value.GetKs().value());
     wpi::PackStruct<kKvOff>(
-        data,
-        units::unit_t<frc::SimpleMotorFeedforward<units::meters>::kv_unit>{
-            value.GetKv()}
-            .value());
+        data, units::unit_t<typename BaseFeedforward::kv_unit>{value.GetKv()}
+                  .value());
     wpi::PackStruct<kKaOff>(
-        data,
-        units::unit_t<frc::SimpleMotorFeedforward<units::meters>::ka_unit>{
-            value.GetKa()}
-            .value());
+        data, units::unit_t<typename BaseFeedforward::ka_unit>{value.GetKa()}
+                  .value());
     wpi::PackStruct<kDtOff>(data, units::second_t{value.GetDt()}.value());
   }
 };
 
 static_assert(
     wpi::StructSerializable<frc::SimpleMotorFeedforward<units::meters>>);
+static_assert(
+    wpi::StructSerializable<frc::SimpleMotorFeedforward<units::feet>>);
 static_assert(
     wpi::StructSerializable<frc::SimpleMotorFeedforward<units::radians>>);

wpimath/src/test/native/cpp/controller/proto/SimpleMotorFeedforwardProtoTest.cpp

@@ -12,12 +12,13 @@
 
 using namespace frc;
 
+template <typename T>
 struct SimpleMotorFeedforwardProtoTestData {
-  using Type = SimpleMotorFeedforward<units::meters>;
+  using Type = SimpleMotorFeedforward<T>;
 
-  inline static const Type kTestData = {units::volt_t{0.4},
-                                        units::volt_t{4.0} / 1_mps,
-                                        units::volt_t{0.7} / 1_mps_sq, 25_ms};
+  inline static const Type kTestData = {
+      units::volt_t{0.4}, units::volt_t{4.0} / (units::unit_t<T>{1} / 1_s),
+      units::volt_t{0.7} / (units::unit_t<T>{1} / 1_s / 1_s), 25_ms};
 
   static void CheckEq(const Type& testData, const Type& data) {
     EXPECT_EQ(testData.GetKs().value(), data.GetKs().value());
@@ -27,5 +28,12 @@ struct SimpleMotorFeedforwardProtoTestData {
   }
 };
 
-INSTANTIATE_TYPED_TEST_SUITE_P(SimpleMotorFeedforwardMeters, ProtoTest,
-                               SimpleMotorFeedforwardProtoTestData);
+INSTANTIATE_TYPED_TEST_SUITE_P(
+    SimpleMotorFeedforwardMeters, ProtoTest,
+    SimpleMotorFeedforwardProtoTestData<units::meters>);
+INSTANTIATE_TYPED_TEST_SUITE_P(
+    SimpleMotorFeedforwardFeet, ProtoTest,
+    SimpleMotorFeedforwardProtoTestData<units::feet>);
+INSTANTIATE_TYPED_TEST_SUITE_P(
+    SimpleMotorFeedforwardRadians, ProtoTest,
+    SimpleMotorFeedforwardProtoTestData<units::radians>);

wpimath/src/test/native/cpp/controller/struct/SimpleMotorFeedforwardStructTest.cpp

@@ -12,12 +12,13 @@
 
 using namespace frc;
 
+template <typename T>
 struct SimpleMotorFeedforwardStructTestData {
-  using Type = SimpleMotorFeedforward<units::meters>;
+  using Type = SimpleMotorFeedforward<T>;
 
-  inline static const Type kTestData = {units::volt_t{0.4},
-                                        units::volt_t{4.0} / 1_mps,
-                                        units::volt_t{0.7} / 1_mps_sq, 25_ms};
+  inline static const Type kTestData = {
+      units::volt_t{0.4}, units::volt_t{4.0} / (units::unit_t<T>{1} / 1_s),
+      units::volt_t{0.7} / (units::unit_t<T>{1} / 1_s / 1_s), 25_ms};
 
   static void CheckEq(const Type& testData, const Type& data) {
     EXPECT_EQ(testData.GetKs().value(), data.GetKs().value());
@@ -27,5 +28,12 @@ struct SimpleMotorFeedforwardStructTestData {
   }
 };
 
-INSTANTIATE_TYPED_TEST_SUITE_P(SimpleMotorFeedforwardMeters, StructTest,
-                               SimpleMotorFeedforwardStructTestData);
+INSTANTIATE_TYPED_TEST_SUITE_P(
+    SimpleMotorFeedforwardMeters, StructTest,
+    SimpleMotorFeedforwardStructTestData<units::meters>);
+INSTANTIATE_TYPED_TEST_SUITE_P(
+    SimpleMotorFeedforwardFeet, StructTest,
+    SimpleMotorFeedforwardStructTestData<units::feet>);
+INSTANTIATE_TYPED_TEST_SUITE_P(
+    SimpleMotorFeedforwardRadians, StructTest,
+    SimpleMotorFeedforwardStructTestData<units::radians>);