Common:

- Fix rare NPE occurs when players disconnect while KB is being processed or a command is being run

Fabric:
- Check if native player object is null before constructing PlatformPlayer

bukkit/src/main/java/me/caseload/knockbacksync/player/BukkitPlayer.java

@@ -78,7 +78,6 @@ public class BukkitPlayer implements PlatformPlayer {
         Preconditions.checkArgument(player != null);
         this.bukkitPlayer = player;
         this.user = PacketEvents.getAPI().getPlayerManager().getUser(bukkitPlayer);
-        Preconditions.checkArgument(user != null);
     }
 
     @Override
@@ -220,7 +219,7 @@ public class BukkitPlayer implements PlatformPlayer {
     }
 
     @Override
-    public User getUser() {
+    public @Nullable User getUser() {
         return this.user;
     }
 

common/src/main/java/me/caseload/knockbacksync/command/subcommand/PingCommand.java

@@ -1,11 +1,13 @@
 package me.caseload.knockbacksync.command.subcommand;
 
+import com.github.retrooper.packetevents.protocol.player.User;
 import me.caseload.knockbacksync.Base;
 import me.caseload.knockbacksync.ConfigWrapper;
 import me.caseload.knockbacksync.command.generic.BuilderCommand;
 import me.caseload.knockbacksync.command.generic.PlayerSelector;
 import me.caseload.knockbacksync.event.KBSyncEventHandler;
 import me.caseload.knockbacksync.event.events.ConfigReloadEvent;
+import me.caseload.knockbacksync.manager.ConfigManager;
 import me.caseload.knockbacksync.manager.PlayerDataManager;
 import me.caseload.knockbacksync.player.PlayerData;
 import me.caseload.knockbacksync.sender.Sender;
@@ -18,6 +20,8 @@ import java.util.function.Predicate;
 
 public class PingCommand implements BuilderCommand {
 
+    private static final ConfigManager configManager = Base.INSTANCE.getConfigManager();
+
     private String pingSelfAvailableMessage;
     private String pingSelfUnavailableMessage;
     private String pingOtherAvailableMessage;
@@ -51,17 +55,17 @@ public class PingCommand implements BuilderCommand {
                         if (context.sender().isConsole()) {
                             context.sender().sendMessage(ChatUtil.translateAlternateColorCodes('&', mustSpecifyPlayerFromConsoleMessage));
                         } else {
-                            context.sender().sendMessage(getPingMessage(context.sender().getUniqueId(), null));
+                            context.sender().sendMessage(getPingMessage(context.sender().getUniqueId(), context.sender().getName(), null, null));
                         }
                     } else {
-                        context.sender().sendMessage(getPingMessage(context.sender().getUniqueId(), targetSelector.getSinglePlayer().getUUID()));
+                        context.sender().sendMessage(getPingMessage(context.sender().getUniqueId(), context.sender().getName(), targetSelector.getSinglePlayer().getUUID(), targetSelector.getSinglePlayer().getName()));
                     }
                 })
         );
         Base.INSTANCE.getEventBus().registerListeners(this);
     }
     private void loadConfig() {
-        ConfigWrapper configWrapper = Base.INSTANCE.getConfigManager().getConfigWrapper();
+        ConfigWrapper configWrapper = configManager.getConfigWrapper();
         pingSelfAvailableMessage = configWrapper.getString("messages.ping.self.available",
                 "Your real ping is &b%ping%&rms. Jitter: &b%jitter%&rms. Spike: &b%spike%&r. Compensated ping: &b%compensated%&rms.");
         pingSelfUnavailableMessage = configWrapper.getString("messages.ping.self.unavailable",
@@ -78,26 +82,27 @@ public class PingCommand implements BuilderCommand {
                 "&cKnockback synchronization is currently disabled for the target player.");
     }
 
-    private String getPingMessage(UUID senderUUID, UUID targetUUID) {
-        PlayerData playerData = null;
+    private String getPingMessage(UUID senderUUID, String senderName, UUID targetUUID, String targetName) {
         boolean isSelf = senderUUID.equals(targetUUID) || targetUUID == null;
-
-        if (senderUUID == null) {
-            senderUUID = targetUUID;
-        }
-
+        String message;
         if (isSelf) {
-            playerData = PlayerDataManager.getPlayerData(Base.INSTANCE.getPlatformServer().getPlayer(senderUUID).getUser());
-            if (playerData == null) {
-                return ChatUtil.translateAlternateColorCodes('&', knockbacksyncDisabledForYouMessage);
-            }
+            message = knockbacksyncDisabledForYouMessage;
+            targetUUID = senderUUID;
+            targetName = senderName;
         } else {
-            playerData = PlayerDataManager.getPlayerData(Base.INSTANCE.getPlatformServer().getPlayer(targetUUID).getUser());
-            if (playerData == null) {
-                return ChatUtil.translateAlternateColorCodes('&', knockbacksyncDisabledForTargetMessage);
-            }
+            message = knockbacksyncDisabledForTargetMessage;
         }
 
+        User targetUser = Base.INSTANCE.getPlatformServer().getPlayer(targetUUID).getUser();
+        if (targetUser == null)
+            return ChatUtil.translateAlternateColorCodes('&',
+                    configManager.getPlayerDisconnectedWhileExecutingCommand()
+            ).replace("%player%", targetName);
+
+        PlayerData playerData = PlayerDataManager.getPlayerData(targetUser);
+        if (playerData == null)
+            return ChatUtil.translateAlternateColorCodes('&', message);
+
         String rawReturnString;
         if (playerData.getPing() == null) {
             rawReturnString = isSelf ? pingSelfUnavailableMessage : pingOtherUnavailableMessage;

common/src/main/java/me/caseload/knockbacksync/command/subcommand/ReloadCommand.java

@@ -14,7 +14,7 @@ import java.util.function.Predicate;
 
 public class ReloadCommand implements BuilderCommand {
 
-    private final ConfigManager configManager = Base.INSTANCE.getConfigManager();
+    private static final ConfigManager configManager = Base.INSTANCE.getConfigManager();
     private String rawReloadMessage = configManager.getConfigWrapper().getString("messages.reload.success", "&aSuccessfully reloaded KnockbackSync.");
 
     public void register(CommandManager<Sender> manager) {

common/src/main/java/me/caseload/knockbacksync/command/subcommand/StatusCommand.java

@@ -14,7 +14,6 @@ import me.caseload.knockbacksync.util.ChatUtil;
 import org.incendo.cloud.CommandManager;
 import org.incendo.cloud.permission.PredicatePermission;
 
-import java.util.UUID;
 import java.util.function.Predicate;
 
 public class StatusCommand implements BuilderCommand {
@@ -85,6 +84,13 @@ public class StatusCommand implements BuilderCommand {
     }
 
     private void showPlayerStatus(Sender sender, PlatformPlayer target) {
+        if (target.getUser() == null) {
+            String message = ChatUtil.translateAlternateColorCodes('&',
+                    configManager.getPlayerDisconnectedWhileExecutingCommand()
+            ).replace("%player%", target.getName());
+            sender.sendMessage(message);
+        }
+
         boolean globalStatus = configManager.isToggled();
         boolean playerStatus = PlayerDataManager.containsPlayerData(target.getUser());
 

common/src/main/java/me/caseload/knockbacksync/command/subcommand/ToggleCommand.java

@@ -1,5 +1,4 @@
 package me.caseload.knockbacksync.command.subcommand;
-import com.github.retrooper.packetevents.protocol.player.Combat;
 import com.github.retrooper.packetevents.protocol.player.User;
 import me.caseload.knockbacksync.Base;
 import me.caseload.knockbacksync.ConfigWrapper;
@@ -11,13 +10,11 @@ import me.caseload.knockbacksync.manager.ConfigManager;
 import me.caseload.knockbacksync.manager.PlayerDataManager;
 import me.caseload.knockbacksync.permission.PermissionChecker;
 import me.caseload.knockbacksync.player.PlatformPlayer;
-import me.caseload.knockbacksync.player.PlayerData;
 import me.caseload.knockbacksync.sender.Sender;
 import me.caseload.knockbacksync.util.ChatUtil;
 import org.incendo.cloud.CommandManager;
 import org.incendo.cloud.permission.PredicatePermission;
 
-import java.util.UUID;
 import java.util.function.Predicate;
 
 public class ToggleCommand implements BuilderCommand {
@@ -70,7 +67,7 @@ public class ToggleCommand implements BuilderCommand {
                     if (targetSelector == null) {
                         // Global toggle
                         if (permissionChecker.hasPermission(sender, TOGGLE_GLOBAL_PERMISSION, false)) {
-                            toggleGlobalKnockback(configManager, sender);
+                            toggleGlobalKnockback(sender);
                         } else {
                             sender.sendMessage(ChatUtil.translateAlternateColorCodes('&', noGlobalPermissionMessage));
                         }
@@ -88,7 +85,7 @@ public class ToggleCommand implements BuilderCommand {
                         if (!configManager.isToggled()) {
                             sender.sendMessage(ChatUtil.translateAlternateColorCodes('&', serverDisabledMessage));
                         } else {
-                            togglePlayerKnockback(target, configManager, sender);
+                            togglePlayerKnockback(target, sender);
                         }
                     }
                 })
@@ -96,7 +93,7 @@ public class ToggleCommand implements BuilderCommand {
     }
 
 
-    private static void toggleGlobalKnockback(ConfigManager configManager, Sender sender) {
+    private static void toggleGlobalKnockback(Sender sender) {
         boolean toggledState = !configManager.isToggled();
         ToggleOnOffEvent toggleOnOffEvent = new ToggleOnOffEvent(toggledState);
         toggleOnOffEvent.post();
@@ -106,8 +103,8 @@ public class ToggleCommand implements BuilderCommand {
         toggledState = toggleOnOffEvent.getStatus();
         configManager.setToggled(toggledState);
 
-        Base.INSTANCE.getConfigManager().getConfigWrapper().set("enabled", toggledState);
-        Base.INSTANCE.getConfigManager().saveConfig();
+        configManager.getConfigWrapper().set("enabled", toggledState);
+        configManager.saveConfig();
 
         String message = ChatUtil.translateAlternateColorCodes('&',
                 toggledState ? configManager.getEnableMessage() : configManager.getDisableMessage()
@@ -115,8 +112,14 @@ public class ToggleCommand implements BuilderCommand {
         sender.sendMessage(ChatUtil.translateAlternateColorCodes('&', message));
     }
 
-    private static void togglePlayerKnockback(PlatformPlayer target, ConfigManager configManager, Sender sender) {
+    private static void togglePlayerKnockback(PlatformPlayer target, Sender sender) {
         User user = target.getUser();
+        if (user == null) {
+            String message = ChatUtil.translateAlternateColorCodes('&',
+                    configManager.getPlayerDisconnectedWhileExecutingCommand()
+            ).replace("%player%", target.getName());
+            sender.sendMessage(message);
+        }
 
         if (PlayerDataManager.shouldExempt(target.getUUID())) {
             String message = ChatUtil.translateAlternateColorCodes('&',

common/src/main/java/me/caseload/knockbacksync/listener/PlayerDamageListener.java

@@ -12,7 +12,7 @@ public abstract class PlayerDamageListener {
             return;
 
         User user = victim.getUser();
-        if (user == null) return; // Prevent errors with fake players
+        if (user == null) return; // Prevent errors with players disconnecting while this is running (or with fake player?)
 
         PlayerData playerData = PlayerDataManager.getPlayerData(user);
         if (playerData == null)

common/src/main/java/me/caseload/knockbacksync/listener/PlayerKnockbackListener.java

@@ -16,7 +16,7 @@ public abstract class PlayerKnockbackListener {
             return;
 
         User user = victim.getUser();
-        if (user == null) return; // Prevent errors with fake players
+        if (user == null) return; // Prevent errors with players disconnecting while this is running (or with fake player?)
 
         PlayerData victimPlayerData = PlayerDataManager.getPlayerData(user);
         if (victimPlayerData == null)

common/src/main/java/me/caseload/knockbacksync/manager/ConfigManager.java

@@ -36,6 +36,7 @@ public class ConfigManager {
     private String playerEnableMessage;
     private String playerDisableMessage;
     private String playerIneligibleMessage;
+    private String playerDisconnectedWhileExecutingCommand;
 
     private AbstractTaskHandle pingTask;
 
@@ -122,6 +123,7 @@ public class ConfigManager {
         playerEnableMessage = configWrapper.getString("messages.toggle.player.enable", "&aSuccessfully enabled KnockbackSync for %player%.");
         playerDisableMessage = configWrapper.getString("messages.toggle.player.disable", "&aSuccessfully &cdisabled &aKnockbackSync for %player%.");
         playerIneligibleMessage = configWrapper.getString("messages.toggle.player.ineligible", "&c%player% is ineligible for KnockbackSync. If you believe this is in error, please contact your server administrators.");
+        playerDisconnectedWhileExecutingCommand = configWrapper.getString("messages.toggle.player.disconnected-while-executing-command", "&c%player% disconnected while executing command.");
     }
 
     public void updateConfig() {

common/src/main/java/me/caseload/knockbacksync/player/PlatformPlayer.java

@@ -52,7 +52,12 @@ public interface PlatformPlayer {
 
     BoundingBox getBoundingBox();
 
-    User getUser();
+    /**
+     * If a player disconnects while we are running the constructor of a PlatformPlayer
+     * PacketEvents.getAPI().getPlayerManager().getUser(bukkitPlayer) may return null
+     * This will make the internal field null and thus this function may return null.
+     */
+    @Nullable User getUser();
 
     void setClientBrand(String brand);
 

common/src/main/resources/config.yml

@@ -194,6 +194,7 @@ messages:
       enable: "&aSuccessfully enabled KnockbackSync for %player%."
       disable: "&aSuccessfully &cdisabled &aKnockbackSync for %player%."
       ineligible: "&c%player% is ineligible for KnockbackSync. If you believe this is in error, please contact your server administrators."
+      disconnected-while-executing-command: "&c%player% disconnected while executing command."
     permission:
       no_global: "&cYou don't have permission to toggle the global setting."
       no_self: "&cYou do not have permission to toggle your knockback."

fabric/src/main/java/me/caseload/knockbacksync/player/FabricPlayer.java

@@ -4,6 +4,7 @@ import com.github.retrooper.packetevents.PacketEvents;
 import com.github.retrooper.packetevents.protocol.player.User;
 import com.github.retrooper.packetevents.protocol.world.BoundingBox;
 import com.github.retrooper.packetevents.util.Vector3d;
+import com.google.common.base.Preconditions;
 import me.caseload.knockbacksync.world.FabricWorld;
 import me.caseload.knockbacksync.world.PlatformWorld;
 import net.minecraft.enchantment.Enchantment;
@@ -33,6 +34,7 @@ public class FabricPlayer implements PlatformPlayer {
     private String clientBrand = "vanilla";
 
     public FabricPlayer(ServerPlayerEntity player) {
+        Preconditions.checkArgument(player != null);
         this.fabricPlayer = player;
         this.user = PacketEvents.getAPI().getPlayerManager().getUser(fabricPlayer);
     }
@@ -156,7 +158,7 @@ public class FabricPlayer implements PlatformPlayer {
     }
 
     @Override
-    public User getUser() {
+    public @Nullable User getUser() {
         return user;
     }