From f9a58aad0843c58a73e62ba79f2cd20eb79fbbdd Mon Sep 17 00:00:00 2001
From: Jason Spangler <jasons@wumple.com>
Date: Sat, 11 Aug 2018 20:09:49 -0500
Subject: [PATCH] Fix for ConcurrentModificationException due to
 ICopyableCap.copyTo()

---
 src/main/java/com/wumple/util/ModConfig.java  |  6 ++-
 .../util/capability/copier/CapCopier.java     |  1 +
 .../util/capability/copier/ICopyableCap.java  | 38 ++++++++++++-------
 3 files changed, 30 insertions(+), 15 deletions(-)

diff --git a/src/main/java/com/wumple/util/ModConfig.java b/src/main/java/com/wumple/util/ModConfig.java
index 1e7439c..108486c 100755
--- a/src/main/java/com/wumple/util/ModConfig.java
+++ b/src/main/java/com/wumple/util/ModConfig.java
@@ -39,8 +39,12 @@ public static class MatchingConfig
     public static class Debugging
     {
         @Name("Debug mode")
-        @Config.Comment("Enable debug features on this menu, display extra debug info.")
+        @Config.Comment("Enable general debug features, display extra debug info.")
         public boolean debug = false;
+        
+        @Name("Placeholder TileEntity")
+        @Config.Comment("Use placeholder TileEntity to hold caps if block has none.  May crash.  May not persist.")
+        public boolean usePlaceholderTileEntity = false;
     }
 
     @Mod.EventBusSubscriber(modid = Reference.MOD_ID)
diff --git a/src/main/java/com/wumple/util/capability/copier/CapCopier.java b/src/main/java/com/wumple/util/capability/copier/CapCopier.java
index 797dfa5..dd07c96 100755
--- a/src/main/java/com/wumple/util/capability/copier/CapCopier.java
+++ b/src/main/java/com/wumple/util/capability/copier/CapCopier.java
@@ -69,6 +69,7 @@ default void onPlaceBlock(BlockEvent.PlaceEvent event)
         ItemStack stack = event.getPlayer().getHeldItem(event.getHand());
         BlockPos pos = event.getPos();
         
+        // this can fail if pos (aka Block at pos) has no TileEntity!
         copyToFrom(pos, stack, world);
     }
     
diff --git a/src/main/java/com/wumple/util/capability/copier/ICopyableCap.java b/src/main/java/com/wumple/util/capability/copier/ICopyableCap.java
index 8ea6236..2771053 100755
--- a/src/main/java/com/wumple/util/capability/copier/ICopyableCap.java
+++ b/src/main/java/com/wumple/util/capability/copier/ICopyableCap.java
@@ -2,6 +2,7 @@
 
 import java.util.List;
 
+import com.wumple.util.ModConfig;
 import com.wumple.util.placeholder.TileEntityPlaceholder;
 
 import net.minecraft.item.ItemStack;
@@ -93,25 +94,34 @@ default void copyTo(BlockPos pos, World world)
     {
         TileEntity tileentity = world.getTileEntity(pos);
 
-        if (tileentity == null)
+        if (ModConfig.zdebugging.usePlaceholderTileEntity)
         {
-            tileentity = getNewTE();
-            if (tileentity != null)
+            if (tileentity == null)
             {
-                Chunk chunk = world.getChunk(pos);
-                // Obvious method doesn't work: world.setTileEntity(pos, tileentity);
-                // Block.hasTileEntity() false would cause Chunk.addTileEntity() to reject
-                tileentity.setWorld(world);
-                tileentity.setPos(pos);
-                tileentity.validate();
-                chunk.getTileEntityMap().put(pos, tileentity);
-                chunk.markDirty();
-                world.addTileEntity(tileentity);
-                // TODO: tileentity will not persist - loading/saving will strip it out since Block.hasTileEntity() false
+                tileentity = getNewTE();
+                if (tileentity != null)
+                {
+                    Chunk chunk = world.getChunk(pos);
+                    // Obvious method doesn't work: world.setTileEntity(pos, tileentity);
+                    // Block.hasTileEntity() false would cause Chunk.addTileEntity() to reject
+                    tileentity.setWorld(world);
+                    tileentity.setPos(pos);
+                    tileentity.validate();
+                    // THIS CAUSES ConcurrentModificationException !!!
+                    // However World.processingLoadedTiles that World.setTileEntity uses is private
+                    chunk.getTileEntityMap().put(pos, tileentity);
+                    chunk.markDirty();
+                    world.addTileEntity(tileentity);
+                    // TODO: tileentity will not persist - loading/saving will strip it out since Block.hasTileEntity() false
+                }
             }
         }
         
-        copyTo(tileentity);
+        if (tileentity != null)
+        {
+            copyTo(tileentity);
+        }
+        // else failure: no TileEntity to copy cap to
     }
     
     default void copyTo(TileEntity tileentity)