Warn users with multiple permissions plugins installed (#3006)

bukkit/src/main/java/me/lucko/luckperms/bukkit/LPBukkitPlugin.java

@@ -305,7 +305,7 @@ public class LPBukkitPlugin extends AbstractLuckPermsPlugin {
                         this.bootstrap.getScheduler().executeSync(() -> {
                             try {
                                 LuckPermsPermissible lpPermissible = new LuckPermsPermissible(player, user, this);
-                                PermissibleInjector.inject(player, lpPermissible);
+                                PermissibleInjector.inject(player, lpPermissible, getLogger());
                             } catch (Throwable t) {
                                 getLogger().severe("Exception thrown when setting up permissions for " +
                                         player.getUniqueId() + " - " + player.getName(), t);

bukkit/src/main/java/me/lucko/luckperms/bukkit/inject/permissible/PermissibleInjector.java

@@ -26,6 +26,7 @@
 package me.lucko.luckperms.bukkit.inject.permissible;
 
 import me.lucko.luckperms.bukkit.util.CraftBukkitImplementation;
+import me.lucko.luckperms.common.plugin.logging.PluginLogger;
 
 import org.bukkit.entity.Player;
 import org.bukkit.permissions.PermissibleBase;
@@ -84,9 +85,10 @@ public final class PermissibleInjector {
      *
      * @param player the player to inject into
      * @param newPermissible the permissible to inject
+     * @param logger the plugin logger
      * @throws Exception propagates any exceptions which were thrown during injection
      */
-    public static void inject(Player player, LuckPermsPermissible newPermissible) throws Exception {
+    public static void inject(Player player, LuckPermsPermissible newPermissible, PluginLogger logger) throws Exception {
 
         // get the existing PermissibleBase held by the player
         PermissibleBase oldPermissible = (PermissibleBase) HUMAN_ENTITY_PERMISSIBLE_FIELD.get(player);
@@ -96,6 +98,15 @@ public final class PermissibleInjector {
             throw new IllegalStateException("LPPermissible already injected into player " + player.toString());
         }
 
+        Class<? extends PermissibleBase> oldClass = oldPermissible.getClass();
+        if (!PermissibleBase.class.equals(oldClass)) {
+            logger.warn("Player " + player.getName() + " already has a custom permissible (" + oldClass.getName() + ")!\n" +
+                    "This is probably because you have multiple permission plugins installed.\n" +
+                    "Please make sure that LuckPerms is the only permission plugin installed on your server!\n" +
+                    "(unless you're performing a migration, in which case, just remember to remove your old " +
+                    "permission plugin once you're done!)");
+        }
+
         // Move attachments over from the old permissible
 
         //noinspection unchecked
@@ -151,4 +162,24 @@ public final class PermissibleInjector {
         }
     }
 
+    public static void checkInjected(Player player, PluginLogger logger) {
+        PermissibleBase permissibleBase;
+        try {
+            permissibleBase = (PermissibleBase) HUMAN_ENTITY_PERMISSIBLE_FIELD.get(player);
+        } catch (IllegalAccessException e) {
+            return; // ignore
+        }
+
+        if (permissibleBase instanceof LuckPermsPermissible) {
+            return; // all gucci
+        }
+
+        Class<? extends PermissibleBase> clazz = permissibleBase.getClass();
+        logger.warn("Player " + player.getName() + " has a non-LuckPerms permissible (" + clazz.getName() + ")!\n" +
+                "This is probably because you have multiple permission plugins installed.\n" +
+                "Please make sure that LuckPerms is the only permission plugin installed on your server!\n" +
+                "(unless you're performing a migration, in which case, just remember to remove your old " +
+                "permission plugin once you're done!)");
+    }
+
 }

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

@@ -203,7 +203,7 @@ public class BukkitConnectionListener extends AbstractConnectionListener impleme
             LuckPermsPermissible lpPermissible = new LuckPermsPermissible(player, user, this.plugin);
 
             // Inject into the player
-            PermissibleInjector.inject(player, lpPermissible);
+            PermissibleInjector.inject(player, lpPermissible, this.plugin.getLogger());
 
         } catch (Throwable t) {
             this.plugin.getLogger().warn("Exception thrown when setting up permissions for " +
@@ -230,6 +230,8 @@ public class BukkitConnectionListener extends AbstractConnectionListener impleme
                 e.disallow(PlayerLoginEvent.Result.KICK_OTHER, "");
             }
         }
+
+        PermissibleInjector.checkInjected(e.getPlayer(), this.plugin.getLogger());
     }
 
     // Wait until the last priority to unload, so plugins can still perform permission checks on this event