Make DigitalOutput a DigitalSource (#2054)

It's perfectly safe to use as a DigitalSource, and can enable some cool tricks.

wpilibc/src/main/native/cpp/DigitalOutput.cpp

@@ -70,6 +70,14 @@ bool DigitalOutput::Get() const {
   return val;
 }
 
+HAL_Handle DigitalOutput::GetPortHandleForRouting() const { return m_handle; }
+
+AnalogTriggerType DigitalOutput::GetAnalogTriggerTypeForRouting() const {
+  return (AnalogTriggerType)0;
+}
+
+bool DigitalOutput::IsAnalogTrigger() const { return false; }
+
 int DigitalOutput::GetChannel() const { return m_channel; }
 
 void DigitalOutput::Pulse(double length) {

wpilibc/src/main/native/include/frc/DigitalOutput.h

@@ -9,7 +9,7 @@
 
 #include <hal/Types.h>
 
-#include "frc/ErrorBase.h"
+#include "frc/DigitalSource.h"
 #include "frc/smartdashboard/Sendable.h"
 #include "frc/smartdashboard/SendableHelper.h"
 
@@ -24,7 +24,7 @@ class SendableBuilder;
  * elsewhere will allocate channels automatically so for those devices it
  * shouldn't be done here.
  */
-class DigitalOutput : public ErrorBase,
+class DigitalOutput : public DigitalSource,
                       public Sendable,
                       public SendableHelper<DigitalOutput> {
  public:
@@ -59,10 +59,26 @@ class DigitalOutput : public ErrorBase,
    */
   bool Get() const;
 
+  // Digital Source Interface
+  /**
+   * @return The HAL Handle to the specified source.
+   */
+  HAL_Handle GetPortHandleForRouting() const override;
+
+  /**
+   * @return The type of analog trigger output to be used. 0 for Digitals
+   */
+  AnalogTriggerType GetAnalogTriggerTypeForRouting() const override;
+
+  /**
+   * Is source an AnalogTrigger
+   */
+  bool IsAnalogTrigger() const override;
+
   /**
    * @return The GPIO channel number that this object represents.
    */
-  int GetChannel() const;
+  int GetChannel() const override;
 
   /**
    * Output a single pulse on the digital output line.

wpilibj/src/main/java/edu/wpi/first/wpilibj/DigitalOutput.java

@@ -18,7 +18,7 @@ import edu.wpi.first.wpilibj.smartdashboard.SendableRegistry;
  * Class to write digital outputs. This class will write digital outputs. Other devices that are
  * implemented elsewhere will automatically allocate digital inputs and outputs as required.
  */
-public class DigitalOutput implements Sendable, AutoCloseable {
+public class DigitalOutput extends DigitalSource implements Sendable, AutoCloseable {
   private static final int invalidPwmGenerator = 0;
   private int m_pwmGenerator = invalidPwmGenerator;
 
@@ -76,6 +76,7 @@ public class DigitalOutput implements Sendable, AutoCloseable {
    *
    * @return The GPIO channel number.
    */
+  @Override
   public int getChannel() {
     return m_channel;
   }
@@ -177,4 +178,34 @@ public class DigitalOutput implements Sendable, AutoCloseable {
     builder.setSmartDashboardType("Digital Output");
     builder.addBooleanProperty("Value", this::get, this::set);
   }
+
+  /**
+   * Is this an analog trigger.
+   *
+   * @return true if this is an analog trigger
+   */
+  @Override
+  public boolean isAnalogTrigger() {
+    return false;
+  }
+
+  /**
+   * Get the analog trigger type.
+   *
+   * @return false
+   */
+  @Override
+  public int getAnalogTriggerTypeForRouting() {
+    return 0;
+  }
+
+  /**
+   * Get the HAL Port Handle.
+   *
+   * @return The HAL Handle to the specified source.
+   */
+  @Override
+  public int getPortHandleForRouting() {
+    return m_handle;
+  }
 }