Add Debouncer (#3590)

Supersedes #2358 with updates and cleanups.

Closes #2482 and closes #2487 because we shouldn't support both
time-based and count-based debouncing approaches.

Co-authored-by: oblarg <emichaelbarnett@gmail.com>

wpilibNewCommands/src/main/java/edu/wpi/first/wpilibj2/command/button/Trigger.java

@@ -6,6 +6,7 @@ package edu.wpi.first.wpilibj2.command.button;
 
 import static edu.wpi.first.wpilibj.util.ErrorMessages.requireNonNullParam;
 
+import edu.wpi.first.wpilibj.Debouncer;
 import edu.wpi.first.wpilibj2.command.Command;
 import edu.wpi.first.wpilibj2.command.CommandScheduler;
 import edu.wpi.first.wpilibj2.command.InstantCommand;
@@ -359,4 +360,23 @@ public class Trigger {
   public Trigger negate() {
     return new Trigger(() -> !get());
   }
+
+  /**
+   * Creates a new debounced trigger from this trigger - it will become active when this trigger has
+   * been active for longer than the specified period.
+   *
+   * @param seconds the debounce period
+   * @return the debounced trigger
+   */
+  public Trigger debounce(double seconds) {
+    return new Trigger(
+        new BooleanSupplier() {
+          Debouncer m_debouncer = new Debouncer(seconds);
+
+          @Override
+          public boolean getAsBoolean() {
+            return m_debouncer.calculate(get());
+          }
+        });
+  }
 }

wpilibNewCommands/src/main/native/cpp/frc2/command/button/Trigger.cpp

@@ -4,6 +4,8 @@
 
 #include "frc2/command/button/Trigger.h"
 
+#include <frc/Debouncer.h>
+
 #include "frc2/command/InstantCommand.h"
 
 using namespace frc2;
@@ -136,3 +138,9 @@ Trigger Trigger::CancelWhenActive(Command* command) {
       });
   return *this;
 }
+
+Trigger Trigger::Debounce(units::second_t debounceTime) {
+  return Trigger([debouncer = frc::Debouncer(debounceTime), *this]() mutable {
+    return debouncer.Calculate(m_isActive());
+  });
+}

wpilibNewCommands/src/main/native/include/frc2/command/button/Trigger.h

@@ -9,6 +9,7 @@
 #include <memory>
 #include <utility>
 
+#include <units/time.h>
 #include <wpi/span.h>
 
 #include "frc2/command/Command.h"
@@ -345,6 +346,15 @@ class Trigger {
     return Trigger([*this] { return !m_isActive(); });
   }
 
+  /**
+   * Creates a new debounced trigger from this trigger - it will become active
+   * when this trigger has been active for longer than the specified period.
+   *
+   * @param debounceTime the debounce period
+   * @return the debounced trigger
+   */
+  Trigger Debounce(units::second_t debounceTime);
+
  private:
   std::function<bool()> m_isActive;
 };

wpilibNewCommands/src/test/java/edu/wpi/first/wpilibj2/command/button/ButtonTest.java

@@ -12,6 +12,7 @@ import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
+import edu.wpi.first.wpilibj.simulation.SimHooks;
 import edu.wpi.first.wpilibj2.command.Command;
 import edu.wpi.first.wpilibj2.command.CommandScheduler;
 import edu.wpi.first.wpilibj2.command.CommandTestBase;
@@ -172,4 +173,26 @@ class ButtonTest extends CommandTestBase {
     assertFalse(button1.negate().get());
     assertTrue(button1.and(button2.negate()).get());
   }
+
+  @Test
+  void debounceTest() {
+    CommandScheduler scheduler = CommandScheduler.getInstance();
+    MockCommandHolder commandHolder = new MockCommandHolder(true);
+    Command command = commandHolder.getMock();
+
+    InternalButton button = new InternalButton();
+    Trigger debounced = button.debounce(0.1);
+
+    debounced.whenActive(command);
+
+    button.setPressed(true);
+    scheduler.run();
+    verify(command, never()).schedule(true);
+
+    SimHooks.stepTiming(0.3);
+
+    button.setPressed(true);
+    scheduler.run();
+    verify(command).schedule(true);
+  }
 }

wpilibNewCommands/src/test/native/cpp/frc2/command/button/ButtonTest.cpp

@@ -2,7 +2,9 @@
 // Open Source Software; you can modify and/or share it under the terms of
 // the WPILib BSD license file in the root directory of this project.
 
-#include "CommandTestBase.h"
+#include <frc/simulation/SimHooks.h>
+
+#include "../CommandTestBase.h"
 #include "frc2/command/CommandScheduler.h"
 #include "frc2/command/RunCommand.h"
 #include "frc2/command/WaitUntilCommand.h"
@@ -190,3 +192,19 @@ TEST_F(ButtonTest, RValueButton) {
   scheduler.Run();
   EXPECT_EQ(counter, 1);
 }
+
+TEST_F(ButtonTest, DebounceTest) {
+  auto& scheduler = CommandScheduler::GetInstance();
+  bool pressed = false;
+  RunCommand command([] {});
+
+  Trigger([&pressed] { return pressed; }).Debounce(100_ms).WhenActive(&command);
+  pressed = true;
+  scheduler.Run();
+  EXPECT_FALSE(scheduler.IsScheduled(&command));
+
+  frc::sim::StepTiming(300_ms);
+
+  scheduler.Run();
+  EXPECT_TRUE(scheduler.IsScheduled(&command));
+}