Defer transaction signing until user clicks Send

src/qt/sendcoinsdialog.cpp

@@ -281,6 +281,8 @@ bool SendCoinsDialog::PrepareSendText(QString& question_string, QString& informa
     }
 
     // prepare transaction for getting txFee earlier
+    // Create unsigned transaction to support creating unsigned PSBTs.
+    // Signing is deferred until the user clicks "Send".
     m_current_transaction = std::make_unique<WalletModelTransaction>(recipients);
     WalletModel::SendCoinsReturn prepareStatus;
 
@@ -500,11 +502,13 @@ void SendCoinsDialog::sendButtonClicked([[maybe_unused]] bool checked)
         return;
     }
 
+    // Create PSBT from the prepared transaction
+    CMutableTransaction mtx = CMutableTransaction{*(m_current_transaction->getWtx())};
+    PartiallySignedTransaction psbtx(mtx);
+
     bool send_failure = false;
     if (retval == QMessageBox::Save) {
         // "Create Unsigned" clicked
-        CMutableTransaction mtx = CMutableTransaction{*(m_current_transaction->getWtx())};
-        PartiallySignedTransaction psbtx(mtx);
         bool complete = false;
         // Fill without signing
         const auto err{model->wallet().fillPSBT(std::nullopt, /*sign=*/false, /*bip32derivs=*/true, /*n_signed=*/nullptr, psbtx, complete)};
@@ -518,8 +522,6 @@ void SendCoinsDialog::sendButtonClicked([[maybe_unused]] bool checked)
         assert(!model->wallet().privateKeysDisabled() || model->wallet().hasExternalSigner());
         bool broadcast = true;
         if (model->wallet().hasExternalSigner()) {
-            CMutableTransaction mtx = CMutableTransaction{*(m_current_transaction->getWtx())};
-            PartiallySignedTransaction psbtx(mtx);
             bool complete = false;
             // Always fill without signing first. This prevents an external signer
             // from being called prematurely and is not expensive.
@@ -540,6 +542,22 @@ void SendCoinsDialog::sendButtonClicked([[maybe_unused]] bool checked)
                     presentPSBT(psbtx);
                 }
             }
+        } else {
+            // Sign the transaction now that the user has confirmed they want to send.
+            bool complete = false;
+            // Fill and sign the PSBT
+            const auto err{model->wallet().fillPSBT(std::nullopt, /*sign=*/true, /*bip32derivs=*/false, /*n_signed=*/nullptr, psbtx, complete)};
+            if (err || !complete) {
+                Q_EMIT message(tr("Send Coins"), tr("Failed to sign transaction."),
+                    CClientUIInterface::MSG_ERROR);
+                send_failure = true;
+                broadcast = false;
+            } else {
+                // Extract the signed transaction
+                CHECK_NONFATAL(FinalizeAndExtractPSBT(psbtx, mtx));
+                const CTransactionRef tx = MakeTransactionRef(mtx);
+                m_current_transaction->setWtx(tx);
+            }
         }
 
         // Broadcast the transaction, unless an external signer was used and it

src/qt/walletmodel.cpp

@@ -203,7 +203,9 @@ WalletModel::SendCoinsReturn WalletModel::prepareTransaction(WalletModelTransact
         int nChangePosRet = -1;
 
         auto& newTx = transaction.getWtx();
-        const auto& res = m_wallet->createTransaction(vecSend, coinControl, /*sign=*/!wallet().privateKeysDisabled(), nChangePosRet, nFeeRequired);
+        // Transaction is not signed during preparation.
+        const bool should_sign = false;
+        const auto& res = m_wallet->createTransaction(vecSend, coinControl, should_sign, nChangePosRet, nFeeRequired);
         newTx = res ? *res : nullptr;
         transaction.setTransactionFee(nFeeRequired);
         if (fSubtractFeeFromAmount && newTx)