Clean up new C++ commands (#2027)

- Remove use of std::set. The only place std::set was actually used was in ParallelRaceGroup,
but this was of minimal utility as ParallelRaceGroup checked for duplicate subsystem
requirements, so it would be very unusual to end up with duplicate commands
in any case; replaced it with a vector.
- Remove use of std::unordered_map except for SelectCommand. Replaced with vector.
- Use pImpl idiom for CommandScheduler
- Minimize include files (remove unnecessary ones)
- Reformat include file order for consistency

wpilibNewCommands/src/main/native/cpp/frc2/command/CommandScheduler.cpp

@@ -7,39 +7,85 @@
 
 #include "frc2/command/CommandScheduler.h"
 
+#include <hal/HALBase.h>
 #include <frc/RobotState.h>
 #include <frc/WPIErrors.h>
 #include <frc/smartdashboard/SendableBuilder.h>
 #include <frc/smartdashboard/SendableRegistry.h>
-#include <frc2/command/CommandGroupBase.h>
-#include <frc2/command/Subsystem.h>
+#include <networktables/NetworkTableEntry.h>
+#include <wpi/DenseMap.h>
 
-#include <hal/HAL.h>
+#include "frc2/command/CommandGroupBase.h"
+#include "frc2/command/CommandState.h"
+#include "frc2/command/Subsystem.h"
 
 using namespace frc2;
+
+class CommandScheduler::Impl {
+ public:
+  // A map from commands to their scheduling state.  Also used as a set of the
+  // currently-running commands.
+  wpi::DenseMap<Command*, CommandState> scheduledCommands;
+
+  // A map from required subsystems to their requiring commands.  Also used as a
+  // set of the currently-required subsystems.
+  wpi::DenseMap<Subsystem*, Command*> requirements;
+
+  // A map from subsystems registered with the scheduler to their default
+  // commands.  Also used as a list of currently-registered subsystems.
+  wpi::DenseMap<Subsystem*, std::unique_ptr<Command>> subsystems;
+
+  // The set of currently-registered buttons that will be polled every
+  // iteration.
+  wpi::SmallVector<wpi::unique_function<void()>, 4> buttons;
+
+  bool disabled{false};
+
+  // NetworkTable entries for use in Sendable impl
+  nt::NetworkTableEntry namesEntry;
+  nt::NetworkTableEntry idsEntry;
+  nt::NetworkTableEntry cancelEntry;
+
+  // Lists of user-supplied actions to be executed on scheduling events for
+  // every command.
+  wpi::SmallVector<Action, 4> initActions;
+  wpi::SmallVector<Action, 4> executeActions;
+  wpi::SmallVector<Action, 4> interruptActions;
+  wpi::SmallVector<Action, 4> finishActions;
+
+  // Flag and queues for avoiding concurrent modification if commands are
+  // scheduled/canceled during run
+
+  bool inRunLoop = false;
+  wpi::DenseMap<Command*, bool> toSchedule;
+  wpi::SmallVector<Command*, 4> toCancel;
+};
+
 template <typename TMap, typename TKey>
 static bool ContainsKey(const TMap& map, TKey keyToCheck) {
   return map.find(keyToCheck) != map.end();
 }
 
-CommandScheduler::CommandScheduler() {
+CommandScheduler::CommandScheduler() : m_impl(new Impl) {
   frc::SendableRegistry::GetInstance().AddLW(this, "Scheduler");
 }
 
+CommandScheduler::~CommandScheduler() {}
+
 CommandScheduler& CommandScheduler::GetInstance() {
   static CommandScheduler scheduler;
   return scheduler;
 }
 
 void CommandScheduler::AddButton(wpi::unique_function<void()> button) {
-  m_buttons.emplace_back(std::move(button));
+  m_impl->buttons.emplace_back(std::move(button));
 }
 
-void CommandScheduler::ClearButtons() { m_buttons.clear(); }
+void CommandScheduler::ClearButtons() { m_impl->buttons.clear(); }
 
 void CommandScheduler::Schedule(bool interruptible, Command* command) {
-  if (m_inRunLoop) {
-    m_toSchedule.try_emplace(command, interruptible);
+  if (m_impl->inRunLoop) {
+    m_impl->toSchedule.try_emplace(command, interruptible);
     return;
   }
 
@@ -49,9 +95,9 @@ void CommandScheduler::Schedule(bool interruptible, Command* command) {
                                "cannot be independently scheduled");
     return;
   }
-  if (m_disabled ||
+  if (m_impl->disabled ||
       (frc::RobotState::IsDisabled() && !command->RunsWhenDisabled()) ||
-      ContainsKey(m_scheduledCommands, command)) {
+      ContainsKey(m_impl->scheduledCommands, command)) {
     return;
   }
 
@@ -61,10 +107,11 @@ void CommandScheduler::Schedule(bool interruptible, Command* command) {
 
   bool isDisjoint = true;
   bool allInterruptible = true;
-  for (auto&& i1 : m_requirements) {
+  for (auto&& i1 : m_impl->requirements) {
     if (requirements.find(i1.first) != requirements.end()) {
       isDisjoint = false;
-      allInterruptible &= m_scheduledCommands[i1.second].IsInterruptible();
+      allInterruptible &=
+          m_impl->scheduledCommands[i1.second].IsInterruptible();
       intersection.emplace_back(i1.second);
     }
   }
@@ -76,12 +123,12 @@ void CommandScheduler::Schedule(bool interruptible, Command* command) {
       }
     }
     command->Initialize();
-    m_scheduledCommands[command] = CommandState{interruptible};
-    for (auto&& action : m_initActions) {
+    m_impl->scheduledCommands[command] = CommandState{interruptible};
+    for (auto&& action : m_impl->initActions) {
       action(*command);
     }
     for (auto&& requirement : requirements) {
-      m_requirements[requirement] = command;
+      m_impl->requirements[requirement] = command;
     }
   }
 }
@@ -115,24 +162,24 @@ void CommandScheduler::Schedule(std::initializer_list<Command*> commands) {
 }
 
 void CommandScheduler::Run() {
-  if (m_disabled) {
+  if (m_impl->disabled) {
     return;
   }
 
   // Run the periodic method of all registered subsystems.
-  for (auto&& subsystem : m_subsystems) {
+  for (auto&& subsystem : m_impl->subsystems) {
     subsystem.getFirst()->Periodic();
   }
 
   // Poll buttons for new commands to add.
-  for (auto&& button : m_buttons) {
+  for (auto&& button : m_impl->buttons) {
     button();
   }
 
-  m_inRunLoop = true;
+  m_impl->inRunLoop = true;
   // Run scheduled commands, remove finished commands.
-  for (auto iterator = m_scheduledCommands.begin();
-       iterator != m_scheduledCommands.end(); iterator++) {
+  for (auto iterator = m_impl->scheduledCommands.begin();
+       iterator != m_impl->scheduledCommands.end(); iterator++) {
     Command* command = iterator->getFirst();
 
     if (!command->RunsWhenDisabled() && frc::RobotState::IsDisabled()) {
@@ -141,53 +188,53 @@ void CommandScheduler::Run() {
     }
 
     command->Execute();
-    for (auto&& action : m_executeActions) {
+    for (auto&& action : m_impl->executeActions) {
       action(*command);
     }
 
     if (command->IsFinished()) {
       command->End(false);
-      for (auto&& action : m_finishActions) {
+      for (auto&& action : m_impl->finishActions) {
         action(*command);
       }
 
       for (auto&& requirement : command->GetRequirements()) {
-        m_requirements.erase(requirement);
+        m_impl->requirements.erase(requirement);
       }
 
-      m_scheduledCommands.erase(iterator);
+      m_impl->scheduledCommands.erase(iterator);
     }
   }
-  m_inRunLoop = false;
+  m_impl->inRunLoop = false;
 
-  for (auto&& commandInterruptible : m_toSchedule) {
+  for (auto&& commandInterruptible : m_impl->toSchedule) {
     Schedule(commandInterruptible.second, commandInterruptible.first);
   }
 
-  for (auto&& command : m_toCancel) {
+  for (auto&& command : m_impl->toCancel) {
     Cancel(command);
   }
 
-  m_toSchedule.clear();
-  m_toCancel.clear();
+  m_impl->toSchedule.clear();
+  m_impl->toCancel.clear();
 
   // Add default commands for un-required registered subsystems.
-  for (auto&& subsystem : m_subsystems) {
-    auto s = m_requirements.find(subsystem.getFirst());
-    if (s == m_requirements.end() && subsystem.getSecond()) {
+  for (auto&& subsystem : m_impl->subsystems) {
+    auto s = m_impl->requirements.find(subsystem.getFirst());
+    if (s == m_impl->requirements.end() && subsystem.getSecond()) {
       Schedule({subsystem.getSecond().get()});
     }
   }
 }
 
 void CommandScheduler::RegisterSubsystem(Subsystem* subsystem) {
-  m_subsystems[subsystem] = nullptr;
+  m_impl->subsystems[subsystem] = nullptr;
 }
 
 void CommandScheduler::UnregisterSubsystem(Subsystem* subsystem) {
-  auto s = m_subsystems.find(subsystem);
-  if (s != m_subsystems.end()) {
-    m_subsystems.erase(s);
+  auto s = m_impl->subsystems.find(subsystem);
+  if (s != m_impl->subsystems.end()) {
+    m_impl->subsystems.erase(s);
   }
 }
 
@@ -206,8 +253,8 @@ void CommandScheduler::UnregisterSubsystem(
 }
 
 Command* CommandScheduler::GetDefaultCommand(const Subsystem* subsystem) const {
-  auto&& find = m_subsystems.find(subsystem);
-  if (find != m_subsystems.end()) {
+  auto&& find = m_impl->subsystems.find(subsystem);
+  if (find != m_impl->subsystems.end()) {
     return find->second.get();
   } else {
     return nullptr;
@@ -215,21 +262,21 @@ Command* CommandScheduler::GetDefaultCommand(const Subsystem* subsystem) const {
 }
 
 void CommandScheduler::Cancel(Command* command) {
-  if (m_inRunLoop) {
-    m_toCancel.emplace_back(command);
+  if (m_impl->inRunLoop) {
+    m_impl->toCancel.emplace_back(command);
     return;
   }
 
-  auto find = m_scheduledCommands.find(command);
-  if (find == m_scheduledCommands.end()) return;
+  auto find = m_impl->scheduledCommands.find(command);
+  if (find == m_impl->scheduledCommands.end()) return;
   command->End(true);
-  for (auto&& action : m_interruptActions) {
+  for (auto&& action : m_impl->interruptActions) {
     action(*command);
   }
-  m_scheduledCommands.erase(find);
-  for (auto&& requirement : m_requirements) {
+  m_impl->scheduledCommands.erase(find);
+  for (auto&& requirement : m_impl->requirements) {
     if (requirement.second == command) {
-      m_requirements.erase(requirement.first);
+      m_impl->requirements.erase(requirement.first);
     }
   }
 }
@@ -247,14 +294,14 @@ void CommandScheduler::Cancel(std::initializer_list<Command*> commands) {
 }
 
 void CommandScheduler::CancelAll() {
-  for (auto&& command : m_scheduledCommands) {
+  for (auto&& command : m_impl->scheduledCommands) {
     Cancel(command.first);
   }
 }
 
 double CommandScheduler::TimeSinceScheduled(const Command* command) const {
-  auto find = m_scheduledCommands.find(command);
-  if (find != m_scheduledCommands.end()) {
+  auto find = m_impl->scheduledCommands.find(command);
+  if (find != m_impl->scheduledCommands.end()) {
     return find->second.TimeSinceInitialized();
   } else {
     return -1;
@@ -281,65 +328,72 @@ bool CommandScheduler::IsScheduled(
 }
 
 bool CommandScheduler::IsScheduled(const Command* command) const {
-  return m_scheduledCommands.find(command) != m_scheduledCommands.end();
+  return m_impl->scheduledCommands.find(command) !=
+         m_impl->scheduledCommands.end();
 }
 
 Command* CommandScheduler::Requiring(const Subsystem* subsystem) const {
-  auto find = m_requirements.find(subsystem);
-  if (find != m_requirements.end()) {
+  auto find = m_impl->requirements.find(subsystem);
+  if (find != m_impl->requirements.end()) {
     return find->second;
   } else {
     return nullptr;
   }
 }
 
-void CommandScheduler::Disable() { m_disabled = true; }
+void CommandScheduler::Disable() { m_impl->disabled = true; }
 
-void CommandScheduler::Enable() { m_disabled = false; }
+void CommandScheduler::Enable() { m_impl->disabled = false; }
 
 void CommandScheduler::OnCommandInitialize(Action action) {
-  m_initActions.emplace_back(std::move(action));
+  m_impl->initActions.emplace_back(std::move(action));
 }
 
 void CommandScheduler::OnCommandExecute(Action action) {
-  m_executeActions.emplace_back(std::move(action));
+  m_impl->executeActions.emplace_back(std::move(action));
 }
 
 void CommandScheduler::OnCommandInterrupt(Action action) {
-  m_interruptActions.emplace_back(std::move(action));
+  m_impl->interruptActions.emplace_back(std::move(action));
 }
 
 void CommandScheduler::OnCommandFinish(Action action) {
-  m_finishActions.emplace_back(std::move(action));
+  m_impl->finishActions.emplace_back(std::move(action));
 }
 
 void CommandScheduler::InitSendable(frc::SendableBuilder& builder) {
   builder.SetSmartDashboardType("Scheduler");
-  m_namesEntry = builder.GetEntry("Names");
-  m_idsEntry = builder.GetEntry("Ids");
-  m_cancelEntry = builder.GetEntry("Cancel");
+  m_impl->namesEntry = builder.GetEntry("Names");
+  m_impl->idsEntry = builder.GetEntry("Ids");
+  m_impl->cancelEntry = builder.GetEntry("Cancel");
 
   builder.SetUpdateTable([this] {
     double tmp[1];
     tmp[0] = 0;
-    auto toCancel = m_cancelEntry.GetDoubleArray(tmp);
+    auto toCancel = m_impl->cancelEntry.GetDoubleArray(tmp);
     for (auto cancel : toCancel) {
       uintptr_t ptrTmp = static_cast<uintptr_t>(cancel);
       Command* command = reinterpret_cast<Command*>(ptrTmp);
-      if (m_scheduledCommands.find(command) != m_scheduledCommands.end()) {
+      if (m_impl->scheduledCommands.find(command) !=
+          m_impl->scheduledCommands.end()) {
         Cancel(command);
       }
-      m_cancelEntry.SetDoubleArray(wpi::ArrayRef<double>{});
+      m_impl->cancelEntry.SetDoubleArray(wpi::ArrayRef<double>{});
     }
 
     wpi::SmallVector<std::string, 8> names;
     wpi::SmallVector<double, 8> ids;
-    for (auto&& command : m_scheduledCommands) {
+    for (auto&& command : m_impl->scheduledCommands) {
       names.emplace_back(command.first->GetName());
       uintptr_t ptrTmp = reinterpret_cast<uintptr_t>(command.first);
       ids.emplace_back(static_cast<double>(ptrTmp));
     }
-    m_namesEntry.SetStringArray(names);
-    m_idsEntry.SetDoubleArray(ids);
+    m_impl->namesEntry.SetStringArray(names);
+    m_impl->idsEntry.SetDoubleArray(ids);
   });
 }
+
+void CommandScheduler::SetDefaultCommandImpl(Subsystem* subsystem,
+                                             std::unique_ptr<Command> command) {
+  m_impl->subsystems[subsystem] = std::move(command);
+}