[wpilib] Add functional interface equivalents to MotorController (#6053)

This does not deprecate any current functionality, but prepares the way for future deprecation.

The drive classes now accept void(double) functions, which makes them more flexible.

The C++ API ended up a bit more verbose, but the Java API is really concise with method references, which is >80% of our userbase. For example:

`DifferentialDrive drive = new DifferentialDrive(m_leftMotor::set, m_rightMotor::set);`

Lambdas can be passed to interoperate with vendor motor controller APIs that don't have e.g., set(double), so CTRE doesn't have to maintain their WPI_ classes anymore.

MotorControllerGroup was replaced with PWMMotorController.addFollower() for PWM motor controllers. Users of CAN motor controllers should use their vendor's follower functionality.

wpilibc/src/main/native/include/frc/motorcontrol/MotorControllerGroup.h

@@ -7,19 +7,25 @@
 #include <functional>
 #include <vector>
 
+#include <wpi/deprecated.h>
 #include <wpi/sendable/Sendable.h>
 #include <wpi/sendable/SendableHelper.h>
 
 #include "frc/motorcontrol/MotorController.h"
 
+WPI_IGNORE_DEPRECATED
+
 namespace frc {
 
 /**
  * Allows multiple MotorController objects to be linked together.
  */
-class MotorControllerGroup : public wpi::Sendable,
-                             public MotorController,
-                             public wpi::SendableHelper<MotorControllerGroup> {
+class [[deprecated(
+    "Use CAN motor controller followers or "
+    "PWMMotorController::AddFollower()")]] MotorControllerGroup
+    : public wpi::Sendable,
+      public MotorController,
+      public wpi::SendableHelper<MotorControllerGroup> {
  public:
   template <class... MotorControllers>
   explicit MotorControllerGroup(MotorController& motorController,
@@ -50,3 +56,5 @@ class MotorControllerGroup : public wpi::Sendable,
 }  // namespace frc
 
 #include "frc/motorcontrol/MotorControllerGroup.inc"
+
+WPI_UNIGNORE_DEPRECATED

wpilibc/src/main/native/include/frc/motorcontrol/NidecBrushless.h

@@ -6,6 +6,7 @@
 
 #include <string>
 
+#include <wpi/deprecated.h>
 #include <wpi/sendable/Sendable.h>
 #include <wpi/sendable/SendableHelper.h>
 
@@ -16,6 +17,8 @@
 
 namespace frc {
 
+WPI_IGNORE_DEPRECATED
+
 /**
  * Nidec Brushless Motor.
  */
@@ -95,4 +98,6 @@ class NidecBrushless : public MotorController,
   double m_speed = 0.0;
 };
 
+WPI_UNIGNORE_DEPRECATED
+
 }  // namespace frc

wpilibc/src/main/native/include/frc/motorcontrol/PWMMotorController.h

@@ -4,9 +4,16 @@
 
 #pragma once
 
+#include <concepts>
+#include <memory>
 #include <string>
 #include <string_view>
+#include <type_traits>
+#include <utility>
+#include <vector>
 
+#include <units/voltage.h>
+#include <wpi/deprecated.h>
 #include <wpi/sendable/Sendable.h>
 #include <wpi/sendable/SendableHelper.h>
 
@@ -17,6 +24,8 @@
 namespace frc {
 class DMA;
 
+WPI_IGNORE_DEPRECATED
+
 /**
  * Common base class for all PWM Motor Controllers.
  */
@@ -40,6 +49,20 @@ class PWMMotorController : public MotorController,
    */
   void Set(double value) override;
 
+  /**
+   * Sets the voltage output of the PWMMotorController. Compensates for
+   * the current bus voltage to ensure that the desired voltage is output even
+   * if the battery voltage is below 12V - highly useful when the voltage
+   * outputs are "meaningful" (e.g. they come from a feedforward calculation).
+   *
+   * <p>NOTE: This function *must* be called regularly in order for voltage
+   * compensation to work properly - unlike the ordinary set function, it is not
+   * "set it and forget it."
+   *
+   * @param output The voltage to output.
+   */
+  void SetVoltage(units::volt_t output) override;
+
   /**
    * Get the recently set value of the PWM. This value is affected by the
    * inversion property. If you want the value that is sent directly to the
@@ -71,6 +94,24 @@ class PWMMotorController : public MotorController,
    */
   void EnableDeadbandElimination(bool eliminateDeadband);
 
+  /**
+   * Make the given PWM motor controller follow the output of this one.
+   *
+   * @param follower The motor controller follower.
+   */
+  void AddFollower(PWMMotorController& follower);
+
+  /**
+   * Make the given PWM motor controller follow the output of this one.
+   *
+   * @param follower The motor controller follower.
+   */
+  template <std::derived_from<PWMMotorController> T>
+  void AddFollower(T&& follower) {
+    m_owningFollowers.emplace_back(
+        std::make_unique<std::decay_t<T>>(std::forward<T>(follower)));
+  }
+
  protected:
   /**
    * Constructor for a PWM Motor %Controller connected via PWM.
@@ -87,8 +128,12 @@ class PWMMotorController : public MotorController,
 
  private:
   bool m_isInverted = false;
+  std::vector<PWMMotorController*> m_nonowningFollowers;
+  std::vector<std::unique_ptr<PWMMotorController>> m_owningFollowers;
 
   PWM* GetPwm() { return &m_pwm; }
 };
 
+WPI_UNIGNORE_DEPRECATED
+
 }  // namespace frc