SPIGOT-4074: Fix createBlockData succeeding on garbage

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

@@ -403,7 +403,10 @@ public class CraftBlockData implements BlockData {
                     data = Block.REGISTRY.b(block) + data;
                 }
 
-                ArgumentBlock arg = new ArgumentBlock(new StringReader(data), false).a(false);
+                StringReader reader = new StringReader(data);
+                ArgumentBlock arg = new ArgumentBlock(reader, false).a(false);
+                Preconditions.checkArgument(!reader.canRead(), "Spurious trailing data");
+
                 blockData = arg.b();
             } catch (CommandSyntaxException ex) {
                 throw new IllegalArgumentException("Could not parse data: " + data, ex);

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

@@ -44,6 +44,13 @@ public class BlockDataTest extends AbstractTestingBase {
         CraftBlockData.newData(Material.CAKE, "minecraft:cake[bites=3]");
     }
 
+    @Test(expected = IllegalArgumentException.class)
+    public void testMistake() {
+        BlockData cakeTest = CraftBlockData.fromData(Blocks.CAKE.getBlockData().set(BlockCake.BITES, 3));
+
+        CraftBlockData.newData(Material.CAKE, cakeTest.toString());
+    }
+
     @Test
     public void testClone() {
         Cake cakeTest = (Cake) CraftBlockData.fromData(Blocks.CAKE.getBlockData().set(BlockCake.BITES, 3));