feat(wasm-utxo): handle PayloadDrop in fromWasmNode converter

Ticket: CSHLD-770

Author: veetragjain

packages/wasm-utxo/js/ast/formatNode.ts

@@ -46,7 +46,8 @@ type Miniscript =
   | Wrap<{ hash256: string }>
   | Wrap<{ hash160: string }>
   | Wrap<{ older: number }>
-  | Wrap<{ after: number }>;
+  | Wrap<{ after: number }>
+  | Wrap<{ payload_drop: string }>;
 
 type TapTree = [TapTree, TapTree] | Miniscript;
 

packages/wasm-utxo/js/ast/fromWasmNode.ts

@@ -114,6 +114,8 @@ function fromUnknown(v: unknown): Node | Node[] {
         return node("multi", value);
       case "MultiA":
         return node("multi_a", value);
+      case "PayloadDrop":
+        return node("payload_drop", value);
 
       case "Tree":
         if (!Array.isArray(value) || value.length !== 2) {

packages/wasm-utxo/test/sbtc.ts

@@ -1,6 +1,7 @@
 import * as assert from "assert";
 import * as crypto from "crypto";
 import { Descriptor } from "../js/index.js";
+import { fromDescriptor, formatNode } from "../js/ast/index.js";
 import { getDefaultXPubs, getUnspendableKey } from "../js/testutils/descriptor/descriptors.js";
 
 // sBTC protocol uses two taproot script leaves:
@@ -245,4 +246,29 @@ describe("sBTC taproot descriptor", function () {
       assert.strictEqual(reclaimLeaf.AndV[0].Drop.Older.relLockTime, 1);
     });
   });
+
+  describe("fromDescriptor (wasm → JS AST)", function () {
+    it("does not throw on a descriptor containing payload_drop", () => {
+      assert.doesNotThrow(() => fromDescriptor(descriptor));
+    });
+
+    it("emits a payload_drop node carrying the original hex payload", () => {
+      const ast = fromDescriptor(descriptor);
+      const formatted = formatNode(ast);
+      assert.ok(
+        formatted.includes(
+          "payload_drop(0000000000013880051ad206838b7981a116c334e8cb1b950afb73eb54a5)",
+        ),
+        `expected payload_drop(<hex>) in formatted AST, got: ${formatted}`,
+      );
+    });
+
+    it("round-trips the reclaim leaf via formatNode", () => {
+      const ast = fromDescriptor(descriptor) as unknown as {
+        tr: [string, [unknown, Parameters<typeof formatNode>[0]]];
+      };
+      const reclaimAst = ast.tr[1][1];
+      assert.strictEqual(formatNode(reclaimAst), RECLAIM_LEAF);
+    });
+  });
 });