[Bleeding] Fixed item duping in certain occasions. Fixes BUKKIT-1310

src/main/java/net/minecraft/server/Block.java

@@ -164,7 +164,7 @@ public class Block {
     public final Material material;
     public float frictionFactor;
     private String name;
-    protected ArrayList<ItemStack> dropList = new ArrayList<ItemStack>(); // CraftBukkit
+    public ArrayList<ItemStack> dropList = new ArrayList<ItemStack>(1); // CraftBukkit
 
     protected Block(int i, Material material) {
         this.bR = true;
@@ -338,6 +338,7 @@ public class Block {
     }
 
     public final void b(World world, int i, int j, int k, int l, int i1) {
+        this.dropList.clear(); // CraftBukkit
         this.dropNaturally(world, i, j, k, l, 1.0F, i1);
         this.doActualDrop(world, i, j, k); // CraftBukkit
     }
@@ -549,10 +550,6 @@ public class Block {
         this.dropList.clear();
     }
 
-    public void setDrops(ArrayList<ItemStack> drops) {
-        this.dropList = drops;
-    }
-
     public ArrayList<ItemStack> calculateDrops(World world, EntityHuman entityhuman, int i, int j, int k, int l) {
         // CraftBukkit end
         if (this.h() && EnchantmentManager.hasSilkTouchEnchantment(entityhuman.inventory)) {

src/main/java/net/minecraft/server/BlockVine.java

@@ -300,9 +300,8 @@ public class BlockVine extends Block {
     // CraftBukkit start - Calculate drops
     public ArrayList<ItemStack> calculateDrops(World world, EntityHuman entityhuman, int i, int j, int k, int l) {
         if (!world.isStatic && entityhuman.U() != null && entityhuman.U().id == Item.SHEARS.id) {
-            super.dropList = new ArrayList<ItemStack>();
             this.a(world, i, j, k, new ItemStack(Block.VINE, 1, 0));
-            return super.dropList;
+            return this.dropList;
         } else {
             return super.calculateDrops(world, entityhuman, i, j, k, l);
         }

src/main/java/org/bukkit/craftbukkit/event/CraftEventFactory.java

@@ -528,9 +528,10 @@ public class CraftEventFactory {
             ((EntityPlayer) player).netServerHandler.sendPacket(packet);
         }
 
-        List<org.bukkit.inventory.ItemStack> drops = new ArrayList<org.bukkit.inventory.ItemStack>();
+        List<ItemStack> calculatedDrops = blockType.calculateDrops(world, player, x, y, z, data);
+        List<org.bukkit.inventory.ItemStack> drops = new ArrayList<org.bukkit.inventory.ItemStack>(calculatedDrops.size());
         if (!creative && player.b(blockType)) {
-            for (ItemStack stack : blockType.calculateDrops(world, player, x, y, z, data)) {
+            for (ItemStack stack : calculatedDrops) {
                 drops.add(new CraftItemStack(stack));
             }
         }
@@ -539,17 +540,17 @@ public class CraftEventFactory {
         world.getServer().getPluginManager().callEvent(event);
 
         if (event.isCancelled()) {
-            blockType.setDrops(new ArrayList<ItemStack>());
+            blockType.dropList.clear();
             // Let the client know the block still exists
             ((EntityPlayer) player).netServerHandler.sendPacket(new Packet53BlockChange(x, y, z, world));
             return true;
         }
 
-        ArrayList<ItemStack> toDrop = new ArrayList<ItemStack>();
+        ArrayList<ItemStack> toDrop = new ArrayList<ItemStack>(drops.size());
         for (org.bukkit.inventory.ItemStack stack : drops) {
             toDrop.add(CraftItemStack.createNMSItemStack(stack));
         }
-        blockType.setDrops(toDrop);
+        blockType.dropList = toDrop;
 
         return false; // Event not cancelled
     }