Fix getLocale on older Bukkit releases (#2915)

bukkit/src/main/java/me/lucko/luckperms/bukkit/listeners/BukkitConnectionListener.java

@@ -28,6 +28,7 @@ package me.lucko.luckperms.bukkit.listeners;
 import me.lucko.luckperms.bukkit.LPBukkitPlugin;
 import me.lucko.luckperms.bukkit.inject.permissible.LuckPermsPermissible;
 import me.lucko.luckperms.bukkit.inject.permissible.PermissibleInjector;
+import me.lucko.luckperms.bukkit.util.PlayerLocaleUtil;
 import me.lucko.luckperms.common.config.ConfigKeys;
 import me.lucko.luckperms.common.locale.Message;
 import me.lucko.luckperms.common.locale.TranslationManager;
@@ -179,7 +180,7 @@ public class BukkitConnectionListener extends AbstractConnectionListener impleme
                 if (this.detectedCraftBukkitOfflineMode) {
                     printCraftBukkitOfflineModeError();
 
-                    Component reason = TranslationManager.render(Message.LOADING_STATE_ERROR_CB_OFFLINE_MODE.build(), player.getLocale());
+                    Component reason = TranslationManager.render(Message.LOADING_STATE_ERROR_CB_OFFLINE_MODE.build(), PlayerLocaleUtil.getLocale(player));
                     e.disallow(PlayerLoginEvent.Result.KICK_OTHER, LegacyComponentSerializer.legacySection().serialize(reason));
                     return;
                 }
@@ -190,7 +191,7 @@ public class BukkitConnectionListener extends AbstractConnectionListener impleme
                         " - denying login.");
             }
 
-            Component reason = TranslationManager.render(Message.LOADING_STATE_ERROR.build(), player.getLocale());
+            Component reason = TranslationManager.render(Message.LOADING_STATE_ERROR.build(), PlayerLocaleUtil.getLocale(player));
             e.disallow(PlayerLoginEvent.Result.KICK_OTHER, LegacyComponentSerializer.legacySection().serialize(reason));
             return;
         }
@@ -208,7 +209,7 @@ public class BukkitConnectionListener extends AbstractConnectionListener impleme
             this.plugin.getLogger().warn("Exception thrown when setting up permissions for " +
                     player.getUniqueId() + " - " + player.getName() + " - denying login.", t);
 
-            Component reason = TranslationManager.render(Message.LOADING_SETUP_ERROR.build(), player.getLocale());
+            Component reason = TranslationManager.render(Message.LOADING_SETUP_ERROR.build(), PlayerLocaleUtil.getLocale(player));
             e.disallow(PlayerLoginEvent.Result.KICK_OTHER, LegacyComponentSerializer.legacySection().serialize(reason));
             return;
         }

bukkit/src/main/java/me/lucko/luckperms/bukkit/util/PlayerLocaleUtil.java

@@ -0,0 +1,67 @@
+/*
+ * This file is part of LuckPerms, licensed under the MIT License.
+ *
+ *  Copyright (c) lucko (Luck) <luck@lucko.me>
+ *  Copyright (c) contributors
+ *
+ *  Permission is hereby granted, free of charge, to any person obtaining a copy
+ *  of this software and associated documentation files (the "Software"), to deal
+ *  in the Software without restriction, including without limitation the rights
+ *  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ *  copies of the Software, and to permit persons to whom the Software is
+ *  furnished to do so, subject to the following conditions:
+ *
+ *  The above copyright notice and this permission notice shall be included in all
+ *  copies or substantial portions of the Software.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ *  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ *  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ *  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ *  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ *  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ *  SOFTWARE.
+ */
+
+package me.lucko.luckperms.bukkit.util;
+
+import org.bukkit.entity.Player;
+
+import java.lang.reflect.Method;
+import java.util.function.Function;
+
+public final class PlayerLocaleUtil {
+    private PlayerLocaleUtil() {}
+
+    private static final Function<Player, String> GET_LOCALE_FUNCTION;
+
+    static {
+        Function<Player, String> function;
+        try {
+            // modern bukkit
+            Player.class.getMethod("getLocale");
+            function = Player::getLocale;
+        } catch (ReflectiveOperationException ex) {
+            try {
+                // legacy spigot method
+                Method legacyMethod = Player.Spigot.class.getMethod("getLocale");
+                function = player -> {
+                    try {
+                        return (String) legacyMethod.invoke(player);
+                    } catch (ReflectiveOperationException e) {
+                        throw new RuntimeException(e);
+                    }
+                };
+            } catch (ReflectiveOperationException e) {
+                // fallback
+                function = player -> null;
+            }
+        }
+        GET_LOCALE_FUNCTION = function;
+    }
+
+    public static String getLocale(Player player) {
+        return GET_LOCALE_FUNCTION.apply(player);
+    }
+
+}