Merge bitcoin-core/gui#872: Menu action to export a watchonly wallet

6573196e63bf4113d332c802f409e3336aebab41 doc: Release note for export watchonly wallet gui action (Ava Chow)
cb51f97f6c59a30c8f79eb066195e9f2e51afd86 gui: Menu action for exporting a watchonly wallet (Ava Chow)
5907a5c7dc228697bcc8646b40dfa2e79e2cace9 gui: Add ExceptionSafeConnect that takes a lambda (Ava Chow)

Pull request description:

  Allows a user to export a watchonly version of their wallet to be used in an airgapped setup.

  Built on bitcoin/bitcoin#32489

ACKs for top commit:
  polespinasa:
    lgtm ACK 6573196e63bf4113d332c802f409e3336aebab41
  pablomartin4btc:
    ACK 6573196e63bf4113d332c802f409e3336aebab41
  hebasto:
    ACK 6573196e63bf4113d332c802f409e3336aebab41.

Tree-SHA512: 30732ecf2ff40dbbd62a8a9974a907fd60f0da89afacce618fb706a02349135dc06d7dfcc11009caba0e020609ab7e586a0ebbeb7cd65940ee2df229d23f0605

Author: hebasto

doc/release-notes-gui-872.md

@@ -0,0 +1,7 @@
+GUI
+---
+
+* A menu action has been added to allow creating a watchonly wallet file from
+  an existing descriptor wallet. This option mirrors the `exportwatchonlywallet`
+  RPC - the exported file can be imported to another node using the Restore
+  Wallet menu action.

src/interfaces/wallet.h

@@ -302,6 +302,9 @@ class Wallet
 
     //! Return pointer to internal wallet class, useful for testing.
     virtual wallet::CWallet* wallet() { return nullptr; }
+
+    //! Export a watchonly wallet file. See CWallet::ExportWatchOnlyWallet
+    virtual util::Result<std::string> exportWatchOnlyWallet(const fs::path& destination) = 0;
 };
 
 //! Wallet chain client that in addition to having chain client methods for

src/qt/bitcoingui.cpp

@@ -377,6 +377,10 @@ void BitcoinGUI::createActions()
     m_mask_values_action->setStatusTip(tr("Mask the values in the Overview tab"));
     m_mask_values_action->setCheckable(true);
 
+    m_export_watchonly_action = new QAction(tr("Export watch-only wallet"), this);
+    m_export_watchonly_action->setEnabled(false);
+    m_export_watchonly_action->setStatusTip(tr("Export a watch-only version of the current wallet that can be restored onto another node."));
+
     connect(quitAction, &QAction::triggered, this, &BitcoinGUI::quitRequested);
     connect(aboutAction, &QAction::triggered, this, &BitcoinGUI::aboutClicked);
     connect(aboutQtAction, &QAction::triggered, qApp, QApplication::aboutQt);
@@ -524,6 +528,18 @@ void BitcoinGUI::createActions()
         });
         connect(m_mask_values_action, &QAction::toggled, this, &BitcoinGUI::setPrivacy);
         connect(m_mask_values_action, &QAction::toggled, this, &BitcoinGUI::enableHistoryAction);
+        GUIUtil::ExceptionSafeConnect(m_export_watchonly_action, &QAction::triggered, [this](bool) {
+            QString destination = GUIUtil::getSaveFileName(this, tr("Save Watch-only Wallet Export"), QString(), QString(), nullptr);
+            if (destination.isEmpty()) return;
+            WalletModel* model = walletFrame->currentWalletModel();
+            if (!Assume(model)) return;
+            util::Result<std::string> export_res = model->wallet().exportWatchOnlyWallet(GUIUtil::QStringToPath(destination));
+            if (export_res) {
+                QMessageBox::information(nullptr, tr("Export Successful"), tr("The wallet has been exported to ") + QString::fromStdString(*export_res));
+            } else {
+                QMessageBox::critical(nullptr, tr("Export Error"), QString::fromStdString(util::ErrorString(export_res).translated));
+            }
+        });
     }
 #endif // ENABLE_WALLET
 
@@ -547,6 +563,7 @@ void BitcoinGUI::createMenuBar()
         file->addSeparator();
         file->addAction(backupWalletAction);
         file->addAction(m_restore_wallet_action);
+        file->addAction(m_export_watchonly_action);
         file->addSeparator();
         file->addAction(openAction);
         file->addAction(signMessageAction);
@@ -832,6 +849,7 @@ void BitcoinGUI::setCurrentWallet(WalletModel* wallet_model)
             break;
         }
     }
+    m_export_watchonly_action->setEnabled(!wallet_model->wallet().privateKeysDisabled());
     updateWindowTitle();
 }
 
@@ -866,6 +884,7 @@ void BitcoinGUI::setWalletActionsEnabled(bool enabled)
     openAction->setEnabled(enabled);
     m_close_wallet_action->setEnabled(enabled);
     m_close_all_wallets_action->setEnabled(enabled);
+    m_export_watchonly_action->setEnabled(enabled);
 }
 
 void BitcoinGUI::createTrayIcon()

src/qt/bitcoingui.h

@@ -167,6 +167,7 @@ class BitcoinGUI : public QMainWindow
     QAction* m_mask_values_action{nullptr};
     QAction* m_migrate_wallet_action{nullptr};
     QMenu* m_migrate_wallet_menu{nullptr};
+    QAction* m_export_watchonly_action{nullptr};
 #ifdef ENABLE_WALLET
     QLabel *m_wallet_selector_label = nullptr;
     QComboBox* m_wallet_selector = nullptr;

src/qt/guiutil.cpp

@@ -972,7 +972,11 @@ void PrintSlotException(
 {
     std::string description = sender->metaObject()->className();
     description += "->";
-    description += receiver->metaObject()->className();
+    if (receiver) {
+        description += receiver->metaObject()->className();
+    } else {
+        description += "anonymous function";
+    }
     PrintExceptionContinue(exception, description);
 }
 

src/qt/guiutil.h

@@ -399,6 +399,38 @@ namespace GUIUtil
             },
             type);
     }
+    template <typename Sender, typename Signal, typename Slot>
+    auto ExceptionSafeConnect(
+        Sender sender, Signal signal, Slot method)
+    {
+        return QObject::connect(
+            sender, signal,
+            [sender, method](auto&&... args) {
+                bool ok{true};
+                try {
+                    method(std::forward<decltype(args)>(args)...);
+                } catch (const NonFatalCheckError& e) {
+                    PrintSlotException(&e, sender, nullptr);
+                    ok = QMetaObject::invokeMethod(
+                        qApp, "handleNonFatalException",
+                        blockingGUIThreadConnection(),
+                        Q_ARG(QString, QString::fromStdString(e.what())));
+                } catch (const std::exception& e) {
+                    PrintSlotException(&e, sender, nullptr);
+                    ok = QMetaObject::invokeMethod(
+                        qApp, "handleRunawayException",
+                        blockingGUIThreadConnection(),
+                        Q_ARG(QString, QString::fromStdString(e.what())));
+                } catch (...) {
+                    PrintSlotException(nullptr, sender, nullptr);
+                    ok = QMetaObject::invokeMethod(
+                        qApp, "handleRunawayException",
+                        blockingGUIThreadConnection(),
+                        Q_ARG(QString, "Unknown failure occurred."));
+                }
+                assert(ok);
+            });
+    }
 
     /**
      * Shows a QDialog instance asynchronously, and deletes it on close.

src/wallet/interfaces.cpp

@@ -21,6 +21,7 @@
 #include <util/ui_change_type.h>
 #include <wallet/coincontrol.h>
 #include <wallet/context.h>
+#include <wallet/export.h>
 #include <wallet/feebumper.h>
 #include <wallet/fees.h>
 #include <wallet/load.h>
@@ -522,6 +523,12 @@ class WalletImpl : public Wallet
     }
     CWallet* wallet() override { return m_wallet.get(); }
 
+    util::Result<std::string> exportWatchOnlyWallet(const fs::path& destination) override {
+        LOCK(m_wallet->cs_wallet);
+        m_wallet->TopUpKeyPool();
+        return ExportWatchOnlyWallet(*m_wallet, destination, m_context);
+    }
+
     WalletContext& m_context;
     std::shared_ptr<CWallet> m_wallet;
 };