Merge #13111: Add unloadwallet RPC

fe65bdec2 bugfix: Delete walletView in WalletFrame::removeWallet (João Barbosa)
0b82bac76 bugfix: Remove dangling wallet env instance (João Barbosa)
0ee77b207 ui: Support wallets unloaded dynamically (João Barbosa)
9f9b50d5f doc: Add release notes for unloadwallet RPC (João Barbosa)
ccbf7ae74 test: Wallet methods are disabled when no wallet is loaded (João Barbosa)
4940a20a4 test: Add functional tests for unloadwallet RPC (João Barbosa)
6608c369b rpc: Add unloadwallet RPC (João Barbosa)
537efe19e rpc: Extract GetWalletNameFromJSONRPCRequest from GetWalletForJSONRPCRequest (João Barbosa)

Pull request description:

  This patch adds wallet unload feature via RPC. It also adds UI support for unloaded wallets.

Tree-SHA512: 7c7f9f32f7a2266d2df574aa6b95f993c3dc82736f93304562122beb8756fb28cd22d03866b48f493c747441f22d30e196b098dec435cc25e035633f090351ea

16 files changed, 194 insertions, 22 deletions

diff --git a/doc/release-notes-pr10740.md b/doc/release-notes-pr10740.md
index c81ea6a4db..a2eb8cd837 100644
--- a/doc/release-notes-pr10740.md
+++ b/doc/release-notes-pr10740.md
@@ -1,9 +1,10 @@
 Dynamic loading and creation of wallets
 ---------------------------------------
 
-Previously, wallets could only be loaded or created at startup, by specifying `-wallet` parameters on the command line or in the bitcoin.conf file. It is now possible to load and create wallets dynamically at runtime:
+Previously, wallets could only be loaded or created at startup, by specifying `-wallet` parameters on the command line or in the bitcoin.conf file. It is now possible to load, create and unload wallets dynamically at runtime:
 
 - Existing wallets can be loaded by calling the `loadwallet` RPC. The wallet can be specified as file/directory basename (which must be located in the `walletdir` directory), or as an absolute path to a file/directory.
 - New wallets can be created (and loaded) by calling the `createwallet` RPC. The provided name must not match a wallet file in the `walletdir` directory or the name of a wallet that is currently loaded.
+- Loaded wallets can be unloaded by calling the `unloadwallet` RPC.
 
 This feature is currently only available through the RPC interface.
diff --git a/src/interfaces/wallet.cpp b/src/interfaces/wallet.cpp
index 3029dbe8e3..e98acba0df 100644
--- a/src/interfaces/wallet.cpp
+++ b/src/interfaces/wallet.cpp
@@ -429,6 +429,10 @@ public:
     bool hdEnabled() override { return m_wallet.IsHDEnabled(); }
     OutputType getDefaultAddressType() override { return m_wallet.m_default_address_type; }
     OutputType getDefaultChangeType() override { return m_wallet.m_default_change_type; }
+    std::unique_ptr<Handler> handleUnload(UnloadFn fn) override
+    {
+        return MakeHandler(m_wallet.NotifyUnload.connect(fn));
+    }
     std::unique_ptr<Handler> handleShowProgress(ShowProgressFn fn) override
     {
         return MakeHandler(m_wallet.ShowProgress.connect(fn));
diff --git a/src/interfaces/wallet.h b/src/interfaces/wallet.h
index 82ae0b14b5..ce42e14eea 100644
--- a/src/interfaces/wallet.h
+++ b/src/interfaces/wallet.h
@@ -242,6 +242,10 @@ public:
     // Get default change type.
     virtual OutputType getDefaultChangeType() = 0;
 
+    //! Register handler for unload message.
+    using UnloadFn = std::function<void()>;
+    virtual std::unique_ptr<Handler> handleUnload(UnloadFn fn) = 0;
+
     //! Register handler for show progress messages.
     using ShowProgressFn = std::function<void(const std::string& title, int progress)>;
     virtual std::unique_ptr<Handler> handleShowProgress(ShowProgressFn fn) = 0;
diff --git a/src/qt/bitcoin.cpp b/src/qt/bitcoin.cpp
index 31d9f936e7..6ddc819113 100644
--- a/src/qt/bitcoin.cpp
+++ b/src/qt/bitcoin.cpp
@@ -238,6 +238,7 @@ public Q_SLOTS:
     /// Handle runaway exceptions. Shows a message box with the problem and quits the program.
     void handleRunawayException(const QString &message);
     void addWallet(WalletModel* walletModel);
+    void removeWallet();
 
 Q_SIGNALS:
     void requestedInitialize();
@@ -467,11 +468,22 @@ void BitcoinApplication::addWallet(WalletModel* walletModel)
 
     connect(walletModel, SIGNAL(coinsSent(WalletModel*, SendCoinsRecipient, QByteArray)),
         paymentServer, SLOT(fetchPaymentACK(WalletModel*, const SendCoinsRecipient&, QByteArray)));
+    connect(walletModel, SIGNAL(unload()), this, SLOT(removeWallet()));
 
     m_wallet_models.push_back(walletModel);
 #endif
 }
 
+void BitcoinApplication::removeWallet()
+{
+#ifdef ENABLE_WALLET
+    WalletModel* walletModel = static_cast<WalletModel*>(sender());
+    m_wallet_models.erase(std::find(m_wallet_models.begin(), m_wallet_models.end(), walletModel));
+    window->removeWallet(walletModel);
+    walletModel->deleteLater();
+#endif
+}
+
 void BitcoinApplication::initializeResult(bool success)
 {
     qDebug() << __func__ << ": Initialization result: " << success;
@@ -491,8 +503,10 @@ void BitcoinApplication::initializeResult(bool success)
 
 #ifdef ENABLE_WALLET
         m_handler_load_wallet = m_node.handleLoadWallet([this](std::unique_ptr<interfaces::Wallet> wallet) {
-            QMetaObject::invokeMethod(this, "addWallet", Qt::QueuedConnection,
-                Q_ARG(WalletModel*, new WalletModel(std::move(wallet), m_node, platformStyle, optionsModel)));
+            WalletModel* wallet_model = new WalletModel(std::move(wallet), m_node, platformStyle, optionsModel, nullptr);
+            // Fix wallet model thread affinity.
+            wallet_model->moveToThread(thread());
+            QMetaObject::invokeMethod(this, "addWallet", Qt::QueuedConnection, Q_ARG(WalletModel*, wallet_model));
         });
 
         for (auto& wallet : m_node.getWallets()) {
diff --git a/src/qt/bitcoingui.cpp b/src/qt/bitcoingui.cpp
index 9f5ea02e14..c6cc631201 100644
--- a/src/qt/bitcoingui.cpp
+++ b/src/qt/bitcoingui.cpp
@@ -120,6 +120,7 @@ BitcoinGUI::BitcoinGUI(interfaces::Node& node, const PlatformStyle *_platformSty
     modalOverlay(0),
     prevBlocks(0),
     spinnerFrame(0),
+    m_wallet_selector_label(nullptr),
     platformStyle(_platformStyle)
 {
     QSettings settings;
@@ -477,6 +478,16 @@ void BitcoinGUI::createToolBars()
 
         m_wallet_selector = new QComboBox();
         connect(m_wallet_selector, SIGNAL(currentIndexChanged(int)), this, SLOT(setCurrentWalletBySelectorIndex(int)));
+
+        m_wallet_selector_label = new QLabel();
+        m_wallet_selector_label->setText(tr("Wallet:") + " ");
+        m_wallet_selector_label->setBuddy(m_wallet_selector);
+
+        m_wallet_selector_label_action = appToolBar->addWidget(m_wallet_selector_label);
+        m_wallet_selector_action = appToolBar->addWidget(m_wallet_selector);
+
+        m_wallet_selector_label_action->setVisible(false);
+        m_wallet_selector_action->setVisible(false);
 #endif
     }
 }
@@ -556,16 +567,29 @@ bool BitcoinGUI::addWallet(WalletModel *walletModel)
     setWalletActionsEnabled(true);
     m_wallet_selector->addItem(display_name, name);
     if (m_wallet_selector->count() == 2) {
-        m_wallet_selector_label = new QLabel();
-        m_wallet_selector_label->setText(tr("Wallet:") + " ");
-        m_wallet_selector_label->setBuddy(m_wallet_selector);
-        appToolBar->addWidget(m_wallet_selector_label);
-        appToolBar->addWidget(m_wallet_selector);
+        m_wallet_selector_label_action->setVisible(true);
+        m_wallet_selector_action->setVisible(true);
     }
     rpcConsole->addWallet(walletModel);
     return walletFrame->addWallet(walletModel);
 }
 
+bool BitcoinGUI::removeWallet(WalletModel* walletModel)
+{
+    if (!walletFrame) return false;
+    QString name = walletModel->getWalletName();
+    int index = m_wallet_selector->findData(name);
+    m_wallet_selector->removeItem(index);
+    if (m_wallet_selector->count() == 0) {
+        setWalletActionsEnabled(false);
+    } else if (m_wallet_selector->count() == 1) {
+        m_wallet_selector_label_action->setVisible(false);
+        m_wallet_selector_action->setVisible(false);
+    }
+    rpcConsole->removeWallet(walletModel);
+    return walletFrame->removeWallet(name);
+}
+
 bool BitcoinGUI::setCurrentWallet(const QString& name)
 {
     if(!walletFrame)
diff --git a/src/qt/bitcoingui.h b/src/qt/bitcoingui.h
index 89c1c73a79..68c35557cc 100644
--- a/src/qt/bitcoingui.h
+++ b/src/qt/bitcoingui.h
@@ -70,6 +70,7 @@ public:
         functionality.
     */
     bool addWallet(WalletModel *walletModel);
+    bool removeWallet(WalletModel* walletModel);
     void removeAllWallets();
 #endif // ENABLE_WALLET
     bool enableWallet;
@@ -122,8 +123,10 @@ private:
     QAction *openRPCConsoleAction;
     QAction *openAction;
     QAction *showHelpMessageAction;
+    QAction *m_wallet_selector_label_action = nullptr;
+    QAction *m_wallet_selector_action = nullptr;
 
-    QLabel *m_wallet_selector_label;
+    QLabel *m_wallet_selector_label = nullptr;
     QComboBox *m_wallet_selector;
 
     QSystemTrayIcon *trayIcon;
diff --git a/src/qt/rpcconsole.cpp b/src/qt/rpcconsole.cpp
index 4550ae9396..e4e8d3535a 100644
--- a/src/qt/rpcconsole.cpp
+++ b/src/qt/rpcconsole.cpp
@@ -713,6 +713,16 @@ void RPCConsole::addWallet(WalletModel * const walletModel)
         ui->WalletSelectorLabel->setVisible(true);
     }
 }
+
+void RPCConsole::removeWallet(WalletModel * const walletModel)
+{
+    const QString name = walletModel->getWalletName();
+    ui->WalletSelector->removeItem(ui->WalletSelector->findData(name));
+    if (ui->WalletSelector->count() == 2) {
+        ui->WalletSelector->setVisible(false);
+        ui->WalletSelectorLabel->setVisible(false);
+    }
+}
 #endif
 
 static QString categoryClass(int category)
diff --git a/src/qt/rpcconsole.h b/src/qt/rpcconsole.h
index a53c4c24f9..0a1a469934 100644
--- a/src/qt/rpcconsole.h
+++ b/src/qt/rpcconsole.h
@@ -48,6 +48,7 @@ public:
 
     void setClientModel(ClientModel *model);
     void addWallet(WalletModel * const walletModel);
+    void removeWallet(WalletModel* const walletModel);
 
     enum MessageClass {
         MC_ERROR,
diff --git a/src/qt/walletframe.cpp b/src/qt/walletframe.cpp
index eb0eba21ef..c5a13f61f4 100644
--- a/src/qt/walletframe.cpp
+++ b/src/qt/walletframe.cpp
@@ -94,6 +94,7 @@ bool WalletFrame::removeWallet(const QString &name)
 
     WalletView *walletView = mapWalletViews.take(name);
     walletStack->removeWidget(walletView);
+    delete walletView;
     return true;
 }
 
diff --git a/src/qt/walletmodel.cpp b/src/qt/walletmodel.cpp
index 3418b1f1a9..389acf0a95 100644
--- a/src/qt/walletmodel.cpp
+++ b/src/qt/walletmodel.cpp
@@ -364,6 +364,12 @@ bool WalletModel::changePassphrase(const SecureString &oldPass, const SecureStri
 }
 
 // Handlers for core signals
+static void NotifyUnload(WalletModel* walletModel)
+{
+    qDebug() << "NotifyUnload";
+    QMetaObject::invokeMethod(walletModel, "unload", Qt::QueuedConnection);
+}
+
 static void NotifyKeyStoreStatusChanged(WalletModel *walletmodel)
 {
     qDebug() << "NotifyKeyStoreStatusChanged";
@@ -411,6 +417,7 @@ static void NotifyWatchonlyChanged(WalletModel *walletmodel, bool fHaveWatchonly
 void WalletModel::subscribeToCoreSignals()
 {
     // Connect signals to wallet
+    m_handler_unload = m_wallet->handleUnload(boost::bind(&NotifyUnload, this));
     m_handler_status_changed = m_wallet->handleStatusChanged(boost::bind(&NotifyKeyStoreStatusChanged, this));
     m_handler_address_book_changed = m_wallet->handleAddressBookChanged(boost::bind(NotifyAddressBookChanged, this, _1, _2, _3, _4, _5));
     m_handler_transaction_changed = m_wallet->handleTransactionChanged(boost::bind(NotifyTransactionChanged, this, _1, _2));
@@ -421,6 +428,7 @@ void WalletModel::subscribeToCoreSignals()
 void WalletModel::unsubscribeFromCoreSignals()
 {
     // Disconnect signals from wallet
+    m_handler_unload->disconnect();
     m_handler_status_changed->disconnect();
     m_handler_address_book_changed->disconnect();
     m_handler_transaction_changed->disconnect();
diff --git a/src/qt/walletmodel.h b/src/qt/walletmodel.h
index 9173fcae52..35ededb121 100644
--- a/src/qt/walletmodel.h
+++ b/src/qt/walletmodel.h
@@ -208,6 +208,7 @@ public:
     AddressTableModel* getAddressTableModel() const { return addressTableModel; }
 private:
     std::unique_ptr<interfaces::Wallet> m_wallet;
+    std::unique_ptr<interfaces::Handler> m_handler_unload;
     std::unique_ptr<interfaces::Handler> m_handler_status_changed;
     std::unique_ptr<interfaces::Handler> m_handler_address_book_changed;
     std::unique_ptr<interfaces::Handler> m_handler_transaction_changed;
@@ -261,6 +262,9 @@ Q_SIGNALS:
     // Watch-only address added
     void notifyWatchonlyChanged(bool fHaveWatchonly);
 
+    // Signal that wallet is about to be removed
+    void unload();
+
 public Q_SLOTS:
     /* Wallet status might have changed */
     void updateStatus();
diff --git a/src/wallet/db.cpp b/src/wallet/db.cpp
index 410dd5009f..01b8eacccb 100644
--- a/src/wallet/db.cpp
+++ b/src/wallet/db.cpp
@@ -694,8 +694,10 @@ void BerkeleyEnvironment::Flush(bool fShutdown)
             if (mapFileUseCount.empty()) {
                 dbenv->log_archive(&listp, DB_ARCH_REMOVE);
                 Close();
-                if (!fMockDb)
+                if (!fMockDb) {
                     fs::remove_all(fs::path(strPath) / "database");
+                }
+                g_dbenvs.erase(strPath);
             }
         }
     }
@@ -794,5 +796,6 @@ void BerkeleyDatabase::Flush(bool shutdown)
 {
     if (!IsDummy()) {
         env->Flush(shutdown);
+        if (shutdown) env = nullptr;
     }
 }
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index fd9e23cb64..3f2255d042 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -40,12 +40,21 @@
 
 static const std::string WALLET_ENDPOINT_BASE = "/wallet/";
 
-std::shared_ptr<CWallet> GetWalletForJSONRPCRequest(const JSONRPCRequest& request)
+bool GetWalletNameFromJSONRPCRequest(const JSONRPCRequest& request, std::string& wallet_name)
 {
     if (request.URI.substr(0, WALLET_ENDPOINT_BASE.size()) == WALLET_ENDPOINT_BASE) {
         // wallet endpoint was used
-        std::string requestedWallet = urlDecode(request.URI.substr(WALLET_ENDPOINT_BASE.size()));
-        std::shared_ptr<CWallet> pwallet = GetWallet(requestedWallet);
+        wallet_name = urlDecode(request.URI.substr(WALLET_ENDPOINT_BASE.size()));
+        return true;
+    }
+    return false;
+}
+
+std::shared_ptr<CWallet> GetWalletForJSONRPCRequest(const JSONRPCRequest& request)
+{
+    std::string wallet_name;
+    if (GetWalletNameFromJSONRPCRequest(request, wallet_name)) {
+        std::shared_ptr<CWallet> pwallet = GetWallet(wallet_name);
         if (!pwallet) throw JSONRPCError(RPC_WALLET_NOT_FOUND, "Requested wallet does not exist or is not loaded");
         return pwallet;
     }
@@ -66,11 +75,6 @@ bool EnsureWalletIsAvailable(CWallet * const pwallet, bool avoidException)
     if (pwallet) return true;
     if (avoidException) return false;
     if (!HasWallets()) {
-        // Note: It isn't currently possible to trigger this error because
-        // wallet RPC methods aren't registered unless a wallet is loaded. But
-        // this error is being kept as a precaution, because it's possible in
-        // the future that wallet RPC methods might get or remain registered
-        // when no wallets are loaded.
         throw JSONRPCError(
             RPC_METHOD_NOT_FOUND, "Method not found (wallet method is disabled because no wallet is loaded)");
     }
@@ -3053,7 +3057,7 @@ static UniValue listwallets(const JSONRPCRequest& request)
     return obj;
 }
 
-UniValue loadwallet(const JSONRPCRequest& request)
+static UniValue loadwallet(const JSONRPCRequest& request)
 {
     if (request.fHelp || request.params.size() != 1)
         throw std::runtime_error(
@@ -3100,7 +3104,7 @@ UniValue loadwallet(const JSONRPCRequest& request)
     return obj;
 }
 
-UniValue createwallet(const JSONRPCRequest& request)
+static UniValue createwallet(const JSONRPCRequest& request)
 {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(
@@ -3147,6 +3151,55 @@ UniValue createwallet(const JSONRPCRequest& request)
     return obj;
 }
 
+static UniValue unloadwallet(const JSONRPCRequest& request)
+{
+    if (request.fHelp || request.params.size() > 1) {
+        throw std::runtime_error(
+            "unloadwallet ( \"wallet_name\" )\n"
+            "Unloads the wallet referenced by the request endpoint otherwise unloads the wallet specified in the argument.\n"
+            "Specifying the wallet name on a wallet endpoint is invalid."
+            "\nArguments:\n"
+            "1. \"wallet_name\"    (string, optional) The name of the wallet to unload.\n"
+            "\nExamples:\n"
+            + HelpExampleCli("unloadwallet", "wallet_name")
+            + HelpExampleRpc("unloadwallet", "wallet_name")
+        );
+    }
+
+    std::string wallet_name;
+    if (GetWalletNameFromJSONRPCRequest(request, wallet_name)) {
+        if (!request.params[0].isNull()) {
+            throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot unload the requested wallet");
+        }
+    } else {
+        wallet_name = request.params[0].get_str();
+    }
+
+    std::shared_ptr<CWallet> wallet = GetWallet(wallet_name);
+    if (!wallet) {
+        throw JSONRPCError(RPC_WALLET_NOT_FOUND, "Requested wallet does not exist or is not loaded");
+    }
+
+    // Release the "main" shared pointer and prevent further notifications.
+    // Note that any attempt to load the same wallet would fail until the wallet
+    // is destroyed (see CheckUniqueFileid).
+    if (!RemoveWallet(wallet)) {
+        throw JSONRPCError(RPC_MISC_ERROR, "Requested wallet already unloaded");
+    }
+    UnregisterValidationInterface(wallet.get());
+
+    // The wallet can be in use so it's not possible to explicitly unload here.
+    // Just notify the unload intent so that all shared pointers are released.
+    // The wallet will be destroyed once the last shared pointer is released.
+    wallet->NotifyUnload();
+
+    // There's no point in waiting for the wallet to unload.
+    // At this point this method should never fail. The unloading could only
+    // fail due to an unexpected error which would cause a process termination.
+
+    return NullUniValue;
+}
+
 static UniValue resendwallettransactions(const JSONRPCRequest& request)
 {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
@@ -4382,6 +4435,7 @@ static const CRPCCommand commands[] =
     { "wallet",             "settxfee",                         &settxfee,                      {"amount"} },
     { "wallet",             "signmessage",                      &signmessage,                   {"address","message"} },
     { "wallet",             "signrawtransactionwithwallet",     &signrawtransactionwithwallet,  {"hexstring","prevtxs","sighashtype"} },
+    { "wallet",             "unloadwallet",                     &unloadwallet,                  {"wallet_name"} },
     { "wallet",             "walletlock",                       &walletlock,                    {} },
     { "wallet",             "walletpassphrasechange",           &walletpassphrasechange,        {"oldpassphrase","newpassphrase"} },
     { "wallet",             "walletpassphrase",                 &walletpassphrase,              {"passphrase","timeout"} },
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index ca785298fd..6255f28b17 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -79,6 +79,15 @@ std::shared_ptr<CWallet> GetWallet(const std::string& name)
     return nullptr;
 }
 
+// Custom deleter for shared_ptr<CWallet>.
+static void ReleaseWallet(CWallet* wallet)
+{
+    LogPrintf("Releasing wallet %s\n", wallet->GetName());
+    wallet->BlockUntilSyncedToCurrentChain();
+    wallet->Flush();
+    delete wallet;
+}
+
 const uint32_t BIP32_HARDENED_KEY_LIMIT = 0x80000000;
 
 const uint256 CMerkleTx::ABANDON_HASH(uint256S("0000000000000000000000000000000000000000000000000000000000000001"));
@@ -1296,7 +1305,7 @@ void CWallet::BlockUntilSyncedToCurrentChain() {
         LOCK(cs_main);
         const CBlockIndex* initialChainTip = chainActive.Tip();
 
-        if (m_last_block_processed->GetAncestor(initialChainTip->nHeight) == initialChainTip) {
+        if (m_last_block_processed && m_last_block_processed->GetAncestor(initialChainTip->nHeight) == initialChainTip) {
             return;
         }
     }
@@ -4066,7 +4075,9 @@ std::shared_ptr<CWallet> CWallet::CreateWalletFromFile(const std::string& name,
 
     int64_t nStart = GetTimeMillis();
     bool fFirstRun = true;
-    std::shared_ptr<CWallet> walletInstance = std::make_shared<CWallet>(name, WalletDatabase::Create(path));
+    // TODO: Can't use std::make_shared because we need a custom deleter but
+    // should be possible to use std::allocate_shared.
+    std::shared_ptr<CWallet> walletInstance(new CWallet(name, WalletDatabase::Create(path)), ReleaseWallet);
     DBErrors nLoadWalletRet = walletInstance->LoadWallet(fFirstRun);
     if (nLoadWalletRet != DBErrors::LOAD_OK)
     {
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index aacbdf81d6..b829394847 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -1100,6 +1100,9 @@ public:
     //! Flush wallet (bitdb flush)
     void Flush(bool shutdown=false);
 
+    /** Wallet is about to be unloaded */
+    boost::signals2::signal<void ()> NotifyUnload;
+
     /**
      * Address book entry changed.
      * @note called with lock cs_wallet held.
diff --git a/test/functional/wallet_multiwallet.py b/test/functional/wallet_multiwallet.py
index a0fbc4a754..3cefd83459 100755
--- a/test/functional/wallet_multiwallet.py
+++ b/test/functional/wallet_multiwallet.py
@@ -234,5 +234,32 @@ class MultiWalletTest(BitcoinTestFramework):
 
         assert new_wallet_name in self.nodes[0].listwallets()
 
+        self.log.info("Test dynamic wallet unloading")
+
+        # Test `unloadwallet` errors
+        assert_raises_rpc_error(-1, "JSON value is not a string as expected", self.nodes[0].unloadwallet)
+        assert_raises_rpc_error(-18, "Requested wallet does not exist or is not loaded", self.nodes[0].unloadwallet, "dummy")
+        assert_raises_rpc_error(-18, "Requested wallet does not exist or is not loaded", node.get_wallet_rpc("dummy").unloadwallet)
+        assert_raises_rpc_error(-8, "Cannot unload the requested wallet", w1.unloadwallet, "w2"),
+
+        # Successfully unload the specified wallet name
+        self.nodes[0].unloadwallet("w1")
+        assert 'w1' not in self.nodes[0].listwallets()
+
+        # Successfully unload the wallet referenced by the request endpoint
+        w2.unloadwallet()
+        assert 'w2' not in self.nodes[0].listwallets()
+
+        # Successfully unload all wallets
+        for wallet_name in self.nodes[0].listwallets():
+            self.nodes[0].unloadwallet(wallet_name)
+        assert_equal(self.nodes[0].listwallets(), [])
+        assert_raises_rpc_error(-32601, "Method not found (wallet method is disabled because no wallet is loaded)", self.nodes[0].getwalletinfo)
+
+        # Successfully load a previously unloaded wallet
+        self.nodes[0].loadwallet('w1')
+        assert_equal(self.nodes[0].listwallets(), ['w1'])
+        assert_equal(w1.getwalletinfo()['walletname'], 'w1')
+
 if __name__ == '__main__':
     MultiWalletTest().main()