refactor: move tapscript finalizer check; add unit test

Author: motorina0

src/psbt.d.ts

@@ -179,6 +179,7 @@ declare type FinalScriptsFunc = (inputIndex: number, // Which input is it?
 input: PsbtInput, // The PSBT input contents
 script: Buffer, // The "meaningful" locking script Buffer (redeemScript for P2SH etc.)
 isSegwit: boolean, // Is it segwit?
+isTapscript: boolean, // Is taproot script path?
 isP2SH: boolean, // Is it P2SH?
 isP2WSH: boolean, // Is it P2WSH?
 eccLib?: TinySecp256k1Interface) => {

src/psbt.js

@@ -289,16 +289,13 @@ class Psbt {
     } = getScriptFromInput(inputIndex, input, this.__CACHE);
     if (!script) throw new Error(`No script found for input #${inputIndex}`);
     checkPartialSigSighashes(input);
-    if (isTapscript && !finalScriptsFunc)
-      throw new Error(
-        `Taproot script-path finalizer required for input #${inputIndex}`,
-      );
     const fn = finalScriptsFunc || getFinalScripts;
     const { finalScriptSig, finalScriptWitness } = fn(
       inputIndex,
       input,
       script,
       isSegwit,
+      isTapscript,
       isP2SH,
       isP2WSH,
       this.__CACHE.__EC_LIB,
@@ -936,12 +933,13 @@ function getFinalScripts(
   input,
   script,
   isSegwit,
+  isTapscript,
   isP2SH,
   isP2WSH,
   eccLib,
 ) {
   const scriptType = classifyScript(script, eccLib);
-  if (!canFinalize(input, script, scriptType))
+  if (isTapscript || !canFinalize(input, script, scriptType))
     throw new Error(`Can not finalize input #${inputIndex}`);
   return prepareFinalScripts(
     script,

test/psbt.spec.ts

@@ -1003,6 +1003,15 @@ describe(`Psbt`, () => {
       psbt.finalizeInput(0, tapscriptFinalizer);
       assert.strictEqual(psbt.toBase64(), f.result);
     });
+
+    it('Failes to finalize a taproot script-path spend when a finalizer is not provided', () => {
+      const f = fixtures.finalizeTaprootScriptPathSpendInput;
+      const psbt = Psbt.fromBase64(f.psbt, { eccLib: ecc });
+
+      assert.throws(() => {
+        psbt.finalizeInput(0);
+      }, new RegExp('Can not finalize input #0'));
+    });
   });
 
   describe('getFeeRate', () => {

test/psbt.utils.ts

@@ -17,6 +17,7 @@ const buildTapscriptFinalizer = (
     input: PsbtInput,
     script: Buffer,
     _isSegwit: boolean,
+    _isTapscript: boolean,
     _isP2SH: boolean,
     _isP2WSH: boolean,
     eccLib?: TinySecp256k1Interface,

ts_src/psbt.ts

@@ -364,17 +364,13 @@ export class Psbt {
 
     checkPartialSigSighashes(input);
 
-    if (isTapscript && !finalScriptsFunc)
-      throw new Error(
-        `Taproot script-path finalizer required for input #${inputIndex}`,
-      );
-
     const fn = finalScriptsFunc || getFinalScripts;
     const { finalScriptSig, finalScriptWitness } = fn(
       inputIndex,
       input,
       script,
       isSegwit,
+      isTapscript,
       isP2SH,
       isP2WSH,
       this.__CACHE.__EC_LIB,
@@ -1224,6 +1220,7 @@ type FinalScriptsFunc = (
   input: PsbtInput, // The PSBT input contents
   script: Buffer, // The "meaningful" locking script Buffer (redeemScript for P2SH etc.)
   isSegwit: boolean, // Is it segwit?
+  isTapscript: boolean, // Is taproot script path?
   isP2SH: boolean, // Is it P2SH?
   isP2WSH: boolean, // Is it P2WSH?
   eccLib?: TinySecp256k1Interface, // optional lib for checking taproot validity
@@ -1237,6 +1234,7 @@ function getFinalScripts(
   input: PsbtInput,
   script: Buffer,
   isSegwit: boolean,
+  isTapscript: boolean,
   isP2SH: boolean,
   isP2WSH: boolean,
   eccLib?: TinySecp256k1Interface,
@@ -1245,7 +1243,7 @@ function getFinalScripts(
   finalScriptWitness: Buffer | undefined;
 } {
   const scriptType = classifyScript(script, eccLib);
-  if (!canFinalize(input, script, scriptType))
+  if (isTapscript || !canFinalize(input, script, scriptType))
     throw new Error(`Can not finalize input #${inputIndex}`);
   return prepareFinalScripts(
     script,