fix(sdk-coin-flrp): improve signature handling in Transaction class and update tests for ImportInCTxBuilder

Author: mohd-kashif

modules/sdk-coin-flrp/src/lib/transaction.ts

@@ -168,10 +168,10 @@ export class Transaction extends BaseTransaction {
       );
     });
 
-    if (hasMatchingAddress) {
-      const signature = await secp256k1.sign(unsignedBytes, prv);
+    const signature = await secp256k1.sign(unsignedBytes, prv);
+    let signatureSet = false;
 
-      let signatureSet = false;
+    if (hasMatchingAddress) {
       // Use address-based slot matching (like AVAX-P)
       let checkSign: CheckSignature | undefined = undefined;
 
@@ -196,11 +196,29 @@ export class Transaction extends BaseTransaction {
 
         if (signatureSet) break;
       }
+    }
 
-      if (!signatureSet) {
-        throw new SigningError('No matching signature slot found for this private key');
+    // Fallback: If address-based matching didn't work (e.g., ImportInC loaded from unsigned tx
+    // where P-chain addresses aren't in addressMaps), try to sign the first empty slot.
+    // This handles the case where we have empty credentials but signer address isn't in the map.
+    if (!signatureSet) {
+      for (const credential of unsignedTx.credentials) {
+        const signatures = credential.getSignatures();
+        for (let i = 0; i < signatures.length; i++) {
+          if (isEmptySignature(signatures[i])) {
+            credential.setSignature(i, signature);
+            signatureSet = true;
+            this._rawSignedBytes = undefined;
+            break;
+          }
+        }
+        if (signatureSet) break;
       }
     }
+
+    if (!signatureSet) {
+      throw new SigningError('No matching signature slot found for this private key');
+    }
   }
 
   toBroadcastFormat(): string {

modules/sdk-coin-flrp/test/unit/lib/importInCTxBuilder.ts

@@ -48,7 +48,5 @@ describe('Flrp Import In C Tx Builder', () => {
       prv2: testData.privateKeys[1],
     },
     txHash: testData.txhash,
-    // Skip signing from recovered unsigned: P-chain signer addresses aren't in the raw ImportInC transaction's address maps
-    skipImportInCTxBuilder: true,
   });
 });

modules/sdk-coin-flrp/test/unit/lib/signFlowTestSuit.ts

@@ -9,7 +9,6 @@ export interface signFlowTestSuitArgs {
   fullSignedTxHex: string;
   privateKey: { prv1: string; prv2: string };
   txHash: string;
-  skipImportInCTxBuilder?: boolean;
 }
 
 /**
@@ -52,18 +51,14 @@ export default function signFlowTestSuit(data: signFlowTestSuitArgs): void {
       tx.id.should.equal(data.txHash);
     });
 
-    // TODO: Skip for ImportInC: P-chain signer addresses aren't in the raw transaction,
-    // so signing a recovered unsigned tx requires addresses to be provided separately.
-    if (!data.skipImportInCTxBuilder) {
-      it('Should half sign tx from unsigned raw tx', async () => {
-        const txBuilder = data.newTxFactory().from(data.unsignedTxHex);
-        txBuilder.sign({ key: data.privateKey.prv1 });
-        const tx = await txBuilder.build();
-        const rawTx = tx.toBroadcastFormat();
-        rawTx.should.equal(data.halfSignedTxHex);
-        tx.id.should.equal(data.txHash);
-      });
-    }
+    it('Should half sign tx from unsigned raw tx', async () => {
+      const txBuilder = data.newTxFactory().from(data.unsignedTxHex);
+      txBuilder.sign({ key: data.privateKey.prv1 });
+      const tx = await txBuilder.build();
+      const rawTx = tx.toBroadcastFormat();
+      rawTx.should.equal(data.halfSignedTxHex);
+      tx.id.should.equal(data.txHash);
+    });
 
     it('Should recover half signed tx from half signed raw tx', async () => {
       const txBuilder = data.newTxFactory().from(data.halfSignedTxHex);
@@ -92,28 +87,23 @@ export default function signFlowTestSuit(data: signFlowTestSuitArgs): void {
       tx.id.should.equal(data.txHash);
     });
 
-    if (!data.skipImportInCTxBuilder) {
-      it('Should full sign a tx from half signed raw tx', async () => {
-        const txBuilder = data.newTxFactory().from(data.halfSignedTxHex);
-        txBuilder.sign({ key: data.privateKey.prv2 });
-        const tx = await txBuilder.build();
-        const rawTx = tx.toBroadcastFormat();
-        rawTx.should.equal(data.fullSignedTxHex);
-        tx.id.should.equal(data.txHash);
-      });
-    }
+    it('Should full sign a tx from half signed raw tx', async () => {
+      const txBuilder = data.newTxFactory().from(data.halfSignedTxHex);
+      txBuilder.sign({ key: data.privateKey.prv2 });
+      const tx = await txBuilder.build();
+      const rawTx = tx.toBroadcastFormat();
+      rawTx.should.equal(data.fullSignedTxHex);
+      tx.id.should.equal(data.txHash);
+    });
 
-    // Skip for ImportInC: P-chain signer addresses aren't in the recovered transaction's address maps
-    if (!data.skipImportInCTxBuilder) {
-      it('Should full sign a tx from unsigned raw tx', async () => {
-        const txBuilder = data.newTxFactory().from(data.unsignedTxHex);
-        txBuilder.sign({ key: data.privateKey.prv1 });
-        txBuilder.sign({ key: data.privateKey.prv2 });
-        const tx = await txBuilder.build();
-        const rawTx = tx.toBroadcastFormat();
-        rawTx.should.equal(data.fullSignedTxHex);
-        tx.id.should.equal(data.txHash);
-      });
-    }
+    it('Should full sign a tx from unsigned raw tx', async () => {
+      const txBuilder = data.newTxFactory().from(data.unsignedTxHex);
+      txBuilder.sign({ key: data.privateKey.prv1 });
+      txBuilder.sign({ key: data.privateKey.prv2 });
+      const tx = await txBuilder.build();
+      const rawTx = tx.toBroadcastFormat();
+      rawTx.should.equal(data.fullSignedTxHex);
+      tx.id.should.equal(data.txHash);
+    });
   });
 }