Fix SessionManager world retention after player quit and world unload

worldguard-bukkit/src/main/java/com/sk89q/worldguard/bukkit/session/BukkitSessionManager.java

@@ -19,6 +19,7 @@
 
 package com.sk89q.worldguard.bukkit.session;
 
+import com.sk89q.worldedit.bukkit.BukkitAdapter;
 import com.sk89q.worldedit.world.World;
 import com.sk89q.worldguard.LocalPlayer;
 import com.sk89q.worldguard.WorldGuard;
@@ -32,6 +33,7 @@
 import org.bukkit.entity.Player;
 import org.bukkit.event.EventHandler;
 import org.bukkit.event.Listener;
+import org.bukkit.event.world.WorldUnloadEvent;
 
 import java.util.function.Consumer;
 
@@ -96,6 +98,16 @@ public void accept(Object ignored) {
                 task.run();
             }
         }
+
+        // Force eviction of expired bypass/session entries. Without this the
+        // caches only evict lazily, so an idle entry can keep a player (and
+        // their world) reachable long after its logical lifetime.
+        cleanUpCaches();
+    }
+
+    @EventHandler
+    public void onWorldUnload(WorldUnloadEvent event) {
+        forgetWorld(BukkitAdapter.adapt(event.getWorld()));
     }
 
     @Override

worldguard-core/src/main/java/com/sk89q/worldguard/session/AbstractSessionManager.java

@@ -164,6 +164,26 @@ public Session getIfPresent(LocalPlayer player) {
         return getIfPresentInternal(new CacheKey(player));
     }
 
+    @Override
+    public void forgetWorld(World world) {
+        checkNotNull(world, "world");
+        bypassCache.asMap().keySet().removeIf(tuple -> tuple.getWorld().equals(world));
+    }
+
+    /**
+     * Force the caches to evict any entries that have already expired.
+     *
+     * <p>The bypass cache uses {@code expireAfterWrite} and the session cache
+     * uses {@code expireAfterAccess}, but Guava only evicts expired entries
+     * lazily during cache operations. When the caches go idle, an expired
+     * entry can keep a strong reference to a player or world alive long after
+     * its logical lifetime. Calling this periodically bounds that retention.</p>
+     */
+    protected void cleanUpCaches() {
+        bypassCache.cleanUp();
+        sessions.cleanUp();
+    }
+
     private Session getIfPresentInternal(CacheKey cacheKey) {
         @Nullable Session session = sessions.getIfPresent(cacheKey);
         if (session != null) {

worldguard-core/src/main/java/com/sk89q/worldguard/session/Session.java

@@ -143,6 +143,9 @@ public void uninitialize(LocalPlayer player) {
         for (Handler handler : handlers.values()) {
             handler.uninitialize(player, location, set);
         }
+
+        lastValid = null;
+        lastRegionSet = null;
     }
 
     /**

worldguard-core/src/main/java/com/sk89q/worldguard/session/SessionManager.java

@@ -108,6 +108,18 @@ public interface SessionManager {
      */
     @Nullable Session getIfPresent(LocalPlayer player);
 
+    /**
+     * Forget any cached bypass information that references the given world.
+     *
+     * <p>This should be called when a world is unloaded so that the bypass
+     * cache does not retain a strong reference to the world (and the players
+     * that were last checked in it) until the cache entries happen to
+     * expire.</p>
+     *
+     * @param world The world to forget
+     */
+    void forgetWorld(World world);
+
     /**
      * Get a player's session. A session will be created if there is no
      * existing session for the player.