fix: "attribute modifier already applied" error, close #348

bukkit/src/main/java/net/william278/husksync/data/BukkitData.java

@@ -643,7 +643,7 @@ public abstract class BukkitData implements Data {
             instance.setBaseValue(attribute == null ? instance.getDefaultValue() : attribute.baseValue());
             instance.getModifiers().forEach(instance::removeModifier);
             if (attribute != null) {
-                attribute.modifiers().forEach(mod -> instance.addModifier(adapt(mod, plugin)));
+                attribute.modifiers().stream().distinct().forEach(mod -> instance.addModifier(adapt(mod, plugin)));
             }
         }
 

common/src/main/java/net/william278/husksync/data/Data.java

@@ -366,7 +366,13 @@ public interface Data {
 
             @Override
             public boolean equals(Object obj) {
-                return obj instanceof Modifier modifier && modifier.uuid().equals(uuid());
+                if (obj instanceof Modifier other) {
+                    if (uuid == null || other.uuid == null) {
+                        return name.equals(other.name);
+                    }
+                    return uuid.equals(other.uuid);
+                }
+                return super.equals(obj);
             }
 
             public double modify(double value) {