---

Goal: When <minecraft:stone> is broken with silk touch, replace all drops with <minecraft:string> * 1.

We use the replacement strategy of REPLACE_ALL_IF_SELECTED here so we only replace the block's drops if an item is selected from our drop pool. Since the only item in the drop pool defines a selector that requires silk touch, the block's drops will only be replaced if the block is broken with silk touch.

---

ZenScript

import mods.dropt.Dropt;

Dropt.list("list_name")

  .add(Dropt.rule()
      .matchBlocks(["minecraft:stone"])
      .replaceStrategy("REPLACE_ALL_IF_SELECTED")
      .addDrop(Dropt.drop()
          .selector(Dropt.weight(1), "REQUIRED")
          .items([<minecraft:string>])
      )
  );

JSON

{
  "rules": [
    {
      "match": {
        "blocks": {
          "blocks": [
            "minecraft:stone:0"
          ]
        }
      },
      "replaceStrategy": "REPLACE_ALL_IF_SELECTED",
      "drops": [
        {
          "selector": {
            "silktouch": "REQUIRED"
          },
          "item": {
            "items" : [
              "minecraft:string"
            ]
          }
        }
      ]
    }
  ]
}

DroptAPI

@SubscribeEvent
public void on(DroptLoadRulesEvent event) {

  List<IDroptRuleBuilder> list = new ArrayList<>();

  list.add(DroptAPI.rule()
      .matchBlocks(new String[]{
          "minecraft:stone"
      })
      .replaceStrategy(EnumReplaceStrategy.REPLACE_ALL_IF_SELECTED)
      .addDrops(new IDroptDropBuilder[]{
          DroptAPI.drop()
            .selector(DroptAPI.weight(1), EnumSilkTouch.REQUIRED)
            .items(new String[]{
                DroptAPI.itemString(Items.STRING)
            })
      })
  );

  ResourceLocation resourceLocation = new ResourceLocation("my_mod_id", "rule_list_name");
  int priority = 0;
  DroptAPI.registerRuleList(resourceLocation, priority, list);
}