Remove finalize, use a Cleaner instead

worldedit-core/src/main/java/com/sk89q/worldedit/EditSession.java

@@ -322,8 +322,7 @@ private Extent wrapExtent(Extent extent, EventBus eventBus, EditSessionEvent eve
         return event.getExtent();
     }
 
-    // pkg private for TracedEditSession only, may later become public API
-    boolean commitRequired() {
+    private boolean commitRequired() {
         if (reorderExtent != null && reorderExtent.commitRequired()) {
             return true;
         }

worldedit-core/src/main/java/com/sk89q/worldedit/TracedEditSession.java

@@ -21,32 +21,59 @@
 
 import com.sk89q.worldedit.extension.platform.Actor;
 import com.sk89q.worldedit.extent.inventory.BlockBag;
+import com.sk89q.worldedit.internal.util.ErrorReporting;
 import com.sk89q.worldedit.util.eventbus.EventBus;
 import com.sk89q.worldedit.world.World;
 
+import java.lang.ref.Cleaner;
 import javax.annotation.Nullable;
 
 /**
  * Internal use only.
  */
 class TracedEditSession extends EditSession {
 
+    private static final Cleaner cleaner = Cleaner.create();
+
+    private static final class TraceRecord implements Runnable {
+        private final Throwable stacktrace = new Throwable("An EditSession was not closed.");
+        private final Actor actor;
+
+        private volatile boolean committed = false;
+
+        private TraceRecord(Actor actor) {
+            this.actor = actor;
+        }
+
+        @Override
+        public void run() {
+            if (!committed) {
+                WorldEdit.logger.warn("####### EDIT SESSION NOT CLOSED #######");
+                WorldEdit.logger.warn("This means that some code did not close their EditSession.");
+                WorldEdit.logger.warn("Here is a stacktrace from the creation of this EditSession:", stacktrace);
+                ErrorReporting.trigger(actor, stacktrace);
+            }
+        }
+    }
+
+    private final TraceRecord record;
+    private final Cleaner.Cleanable cleanable;
+
     TracedEditSession(EventBus eventBus, @Nullable World world, int maxBlocks, @Nullable BlockBag blockBag,
                       @Nullable Actor actor,
                       boolean tracing) {
         super(eventBus, world, maxBlocks, blockBag, actor, tracing);
+        this.record = new TraceRecord(actor);
+        this.cleanable = cleaner.register(this, record);
     }
 
-    private final Throwable stacktrace = new Throwable("Creation trace.");
-
     @Override
-    protected void finalize() throws Throwable {
-        super.finalize();
-
-        if (commitRequired()) {
-            WorldEdit.logger.warn("####### LEFTOVER BUFFER BLOCKS DETECTED #######");
-            WorldEdit.logger.warn("This means that some code did not flush their EditSession.");
-            WorldEdit.logger.warn("Here is a stacktrace from the creation of this EditSession:", stacktrace);
+    public void close() {
+        try {
+            super.close();
+        } finally {
+            this.record.committed = true;
+            cleanable.clean();
         }
     }
 }

worldedit-core/src/main/java/com/sk89q/worldedit/command/tool/QueryTool.java

@@ -19,7 +19,6 @@
 
 package com.sk89q.worldedit.command.tool;
 
-import com.sk89q.worldedit.EditSession;
 import com.sk89q.worldedit.LocalConfiguration;
 import com.sk89q.worldedit.LocalSession;
 import com.sk89q.worldedit.entity.Player;
@@ -53,9 +52,8 @@ public boolean canUse(Actor player) {
     public boolean actPrimary(Platform server, LocalConfiguration config, Player player, LocalSession session, Location clicked, @Nullable Direction face) {
 
         World world = (World) clicked.getExtent();
-        EditSession editSession = session.createEditSession(player);
         BlockVector3 blockPoint = clicked.toVector().toBlockPoint();
-        BaseBlock block = editSession.getFullBlock(blockPoint);
+        BaseBlock block = player.getExtent().getFullBlock(blockPoint);
 
         TextComponent.Builder builder = TextComponent.builder();
         builder.append(TextComponent.of("@" + clicked.toVector().toBlockPoint() + ": ", TextColor.BLUE));

worldedit-core/src/main/java/com/sk89q/worldedit/extension/platform/PlatformCommandManager.java

@@ -101,6 +101,7 @@
 import com.sk89q.worldedit.internal.command.CommandRegistrationHandler;
 import com.sk89q.worldedit.internal.command.exception.ExceptionConverter;
 import com.sk89q.worldedit.internal.command.exception.WorldEditExceptionConverter;
+import com.sk89q.worldedit.internal.util.ErrorReporting;
 import com.sk89q.worldedit.internal.util.LogManagerCompat;
 import com.sk89q.worldedit.internal.util.Substring;
 import com.sk89q.worldedit.regions.Region;
@@ -591,9 +592,8 @@ private MemoizingValueAccess initializeInjectedValues(Arguments arguments, Actor
     }
 
     private void handleUnknownException(Actor actor, Throwable t) {
-        actor.printError(TranslatableComponent.of("worldedit.command.error.report"));
-        actor.print(TextComponent.of(t.getClass().getName() + ": " + t.getMessage()));
         LOGGER.error("An unexpected error while handling a WorldEdit command", t);
+        ErrorReporting.trigger(actor, t);
     }
 
     @Subscribe

worldedit-core/src/main/java/com/sk89q/worldedit/internal/util/ErrorReporting.java

@@ -0,0 +1,24 @@
+package com.sk89q.worldedit.internal.util;
+
+import com.google.common.base.Throwables;
+import com.sk89q.worldedit.extension.platform.Actor;
+import com.sk89q.worldedit.util.formatting.text.TextComponent;
+import com.sk89q.worldedit.util.formatting.text.TranslatableComponent;
+import com.sk89q.worldedit.util.formatting.text.event.HoverEvent;
+
+/**
+ * Simple class for handling error reporting to users.
+ */
+public class ErrorReporting {
+    public static void trigger(Actor actor, Throwable error) {
+        actor.printError(TranslatableComponent.of("worldedit.command.error.report"));
+        actor.print(
+            TextComponent.builder(error.getClass().getName() + ": " + error.getMessage())
+                .hoverEvent(HoverEvent.showText(TextComponent.of(Throwables.getStackTraceAsString(error))))
+                .build()
+        );
+    }
+
+    private ErrorReporting() {
+    }
+}