PaperMC/paper-server/patches/unapplied/net/minecraft/network/syncher/SynchedEntityData.java.patch

--- a/net/minecraft/network/syncher/SynchedEntityData.java
+++ b/net/minecraft/network/syncher/SynchedEntityData.java
@@ -50,8 +50,8 @@
         }
     }
 
-    private <T> SynchedEntityData.DataItem<T> getItem(EntityDataAccessor<T> key) {
-        return this.itemsById[key.id()];
+    public <T> SynchedEntityData.DataItem<T> getItem(EntityDataAccessor<T> key) { // Paper - public
+        return (SynchedEntityData.DataItem<T>) this.itemsById[key.id()]; // CraftBukkit - decompile error
     }
 
     public <T> T get(EntityDataAccessor<T> data) {
@@ -74,6 +74,13 @@
 
     }
 
+    // CraftBukkit start - add method from above
+    public <T> void markDirty(EntityDataAccessor<T> datawatcherobject) {
+        this.getItem(datawatcherobject).setDirty(true);
+        this.isDirty = true;
+    }
+    // CraftBukkit end
+
     public boolean isDirty() {
         return this.isDirty;
     }
@@ -140,10 +147,24 @@
         if (!Objects.equals(from.serializer(), to.accessor.serializer())) {
             throw new IllegalStateException(String.format(Locale.ROOT, "Invalid entity data item type for field %d on entity %s: old=%s(%s), new=%s(%s)", to.accessor.id(), this.entity, to.value, to.value.getClass(), from.value, from.value.getClass()));
         } else {
-            to.setValue(from.value);
+            to.setValue((T) from.value); // CraftBukkit - decompile error
         }
     }
 
+    // Paper start
+    // We need to pack all as we cannot rely on "non default values" or "dirty" ones.
+    // Because these values can possibly be desynced on the client.
+    @Nullable
+    public List<SynchedEntityData.DataValue<?>> packAll() {
+        final List<SynchedEntityData.DataValue<?>> list = new ArrayList<>();
+        for (final DataItem<?> dataItem : this.itemsById) {
+            list.add(dataItem.value());
+        }
+
+        return list;
+    }
+    // Paper end
+
     public static class DataItem<T> {
 
         final EntityDataAccessor<T> accessor;