SPIGOT-4214: Catch attempts to create BlockData for items

src/main/java/org/bukkit/craftbukkit/block/data/CraftBlockData.java

@@ -417,6 +417,8 @@ public class CraftBlockData implements BlockData {
     }
 
     public static CraftBlockData newData(Material material, String data) {
+        Preconditions.checkArgument(material == null || material.isBlock(), "Cannot get data for not block %s", material);
+
         IBlockData blockData;
         Block block = CraftMagicNumbers.getBlock(material);
 

src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java

@@ -84,6 +84,7 @@ public final class CraftMagicNumbers implements UnsafeValues {
 
         for (Material material : Material.values()) {
             MinecraftKey key = key(material);
+            // TODO: only register if block/item?
             MATERIAL_ITEM.put(material, Item.REGISTRY.get(key));
             MATERIAL_BLOCK.put(material, Block.REGISTRY.get(key));
         }

src/test/java/org/bukkit/BlockDataTest.java

@@ -51,6 +51,16 @@ public class BlockDataTest extends AbstractTestingBase {
         CraftBlockData.newData(Material.CAKE, cakeTest.toString());
     }
 
+    @Test(expected = IllegalArgumentException.class)
+    public void testItem() {
+        CraftBlockData.newData(Material.DIAMOND_AXE, null);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testItemParse() {
+        CraftBlockData.newData(null, "minecraft:diamond_axe");
+    }
+
     @Test
     public void testClone() {
         Cake cakeTest = (Cake) CraftBlockData.fromData(Blocks.CAKE.getBlockData().set(BlockCake.BITES, 3));