feat(wasm-utxo): add Miniscript fromStringExt for drop wrapper support

Ticket: CSHLD-770

Author: veetragjain

packages/wasm-utxo/js/index.ts

@@ -74,6 +74,16 @@ declare module "./wasm/wasm_utxo.js" {
   namespace WrapMiniscript {
     function fromString(miniscript: string, ctx: ScriptContext): WrapMiniscript;
     function fromBitcoinScript(script: Uint8Array, ctx: ScriptContext): WrapMiniscript;
+    function fromStringExt(
+      miniscript: string,
+      ctx: ScriptContext,
+      extParams?: ExtParamsConfig,
+    ): WrapMiniscript;
+    function fromBitcoinScriptExt(
+      script: Uint8Array,
+      ctx: ScriptContext,
+      extParams?: ExtParamsConfig,
+    ): WrapMiniscript;
   }
 
   /** BIP32 derivation data from a PSBT */

packages/wasm-utxo/src/wasm/miniscript.rs

@@ -1,6 +1,8 @@
 use crate::error::WasmUtxoError;
+use crate::wasm::try_from_js_value::get_field;
 use crate::wasm::try_into_js_value::TryIntoJsValue;
 use miniscript::bitcoin::{PublicKey, XOnlyPublicKey};
+use miniscript::miniscript::analyzable::ExtParams;
 use miniscript::{bitcoin, Legacy, Miniscript, Segwitv0, Tap};
 use std::fmt;
 use std::str::FromStr;
@@ -86,6 +88,85 @@ impl WrapMiniscript {
             _ => Err(WasmUtxoError::new("Invalid context type")),
         }
     }
+
+    #[wasm_bindgen(js_name = fromStringExt, skip_typescript)]
+    pub fn from_string_ext(
+        script: &str,
+        context_type: &str,
+        ext_params_config: JsValue,
+    ) -> Result<WrapMiniscript, WasmUtxoError> {
+        let params = build_ext_params(&ext_params_config)?;
+        match context_type {
+            "tap" => Ok(WrapMiniscript::from(
+                Miniscript::<XOnlyPublicKey, Tap>::from_str_ext(script, &params)
+                    .map_err(WasmUtxoError::from)?,
+            )),
+            "segwitv0" => Ok(WrapMiniscript::from(
+                Miniscript::<PublicKey, Segwitv0>::from_str_ext(script, &params)
+                    .map_err(WasmUtxoError::from)?,
+            )),
+            "legacy" => Ok(WrapMiniscript::from(
+                Miniscript::<PublicKey, Legacy>::from_str_ext(script, &params)
+                    .map_err(WasmUtxoError::from)?,
+            )),
+            _ => Err(WasmUtxoError::new("Invalid context type")),
+        }
+    }
+
+    #[wasm_bindgen(js_name = fromBitcoinScriptExt, skip_typescript)]
+    pub fn from_bitcoin_script_ext(
+        script: &[u8],
+        context_type: &str,
+        ext_params_config: JsValue,
+    ) -> Result<WrapMiniscript, WasmUtxoError> {
+        let params = build_ext_params(&ext_params_config)?;
+        let script = bitcoin::Script::from_bytes(script);
+        match context_type {
+            "tap" => Ok(WrapMiniscript::from(
+                Miniscript::<XOnlyPublicKey, Tap>::decode_with_ext(script, &params)
+                    .map_err(WasmUtxoError::from)?,
+            )),
+            "segwitv0" => Ok(WrapMiniscript::from(
+                Miniscript::<PublicKey, Segwitv0>::decode_with_ext(script, &params)
+                    .map_err(WasmUtxoError::from)?,
+            )),
+            "legacy" => Ok(WrapMiniscript::from(
+                Miniscript::<PublicKey, Legacy>::decode_with_ext(script, &params)
+                    .map_err(WasmUtxoError::from)?,
+            )),
+            _ => Err(WasmUtxoError::new("Invalid context type")),
+        }
+    }
+}
+
+fn build_ext_params(config: &JsValue) -> Result<ExtParams, WasmUtxoError> {
+    let flag = |key| -> Result<bool, WasmUtxoError> {
+        if config.is_undefined() || config.is_null() {
+            return Ok(false);
+        }
+        Ok(get_field::<Option<bool>>(config, key)?.unwrap_or(false))
+    };
+
+    let mut params = ExtParams::sane().drop();
+    if flag("topUnsafe")? {
+        params = params.top_unsafe();
+    }
+    if flag("resourceLimitations")? {
+        params = params.exceed_resource_limitations();
+    }
+    if flag("timelockMixing")? {
+        params = params.timelock_mixing();
+    }
+    if flag("malleability")? {
+        params = params.malleability();
+    }
+    if flag("repeatedPk")? {
+        params = params.repeated_pk();
+    }
+    if flag("rawPkh")? {
+        params = params.raw_pkh();
+    }
+    Ok(params)
 }
 
 impl From<Miniscript<XOnlyPublicKey, Tap>> for WrapMiniscript {

packages/wasm-utxo/test/sbtc.ts

@@ -1,6 +1,6 @@
 import * as assert from "assert";
 import * as crypto from "crypto";
-import { Descriptor } from "../js/index.js";
+import { Descriptor, Miniscript } from "../js/index.js";
 import { fromDescriptor, formatNode } from "../js/ast/index.js";
 import { getDefaultXPubs, getUnspendableKey } from "../js/testutils/descriptor/descriptors.js";
 
@@ -247,6 +247,46 @@ describe("sBTC taproot descriptor", function () {
     });
   });
 
+  describe("Miniscript.fromStringExt / fromBitcoinScriptExt (reclaim leaf)", function () {
+    it("Miniscript.fromString rejects r:older (sanity baseline)", () => {
+      assert.throws(
+        () => Miniscript.fromString(RECLAIM_LEAF, "tap"),
+        /r:older|drop|wrapper|unexpected/i,
+        "expected fromString to reject the drop wrapper",
+      );
+    });
+
+    it("Miniscript.fromStringExt parses the reclaim leaf with drop enabled", () => {
+      const ms = Miniscript.fromStringExt(RECLAIM_LEAF, "tap");
+      assert.ok(ms);
+      assert.strictEqual(ms.toString(), RECLAIM_LEAF);
+    });
+
+    it("Miniscript.fromStringExt accepts an explicit empty config", () => {
+      const ms = Miniscript.fromStringExt(RECLAIM_LEAF, "tap", {});
+      assert.ok(ms);
+      assert.strictEqual(ms.toString(), RECLAIM_LEAF);
+    });
+
+    it("Miniscript.fromStringExt round-trips encode() back to RECLAIM_SCRIPT_HEX", () => {
+      const ms = Miniscript.fromStringExt(RECLAIM_LEAF, "tap");
+      assert.strictEqual(Buffer.from(ms.encode()).toString("hex"), RECLAIM_SCRIPT_HEX);
+    });
+
+    it("Miniscript.fromBitcoinScriptExt decodes RECLAIM_SCRIPT_HEX", () => {
+      const ms = Miniscript.fromBitcoinScriptExt(Buffer.from(RECLAIM_SCRIPT_HEX, "hex"), "tap", {});
+      assert.ok(ms);
+      assert.strictEqual(ms.toString(), RECLAIM_LEAF);
+    });
+
+    it("Miniscript.fromStringExt rejects unknown context_type", () => {
+      assert.throws(
+        () => Miniscript.fromStringExt(RECLAIM_LEAF, "bogus" as never, {}),
+        /Invalid context type/,
+      );
+    });
+  });
+
   describe("fromDescriptor (wasm → JS AST)", function () {
     it("does not throw on a descriptor containing payload_drop", () => {
       assert.doesNotThrow(() => fromDescriptor(descriptor));