Add warnings for old server versions owncloud#4523

* A tray message on every start up
* Red message in account settings
* Folders are paused when the server version switches to
  an unsupported one

src/gui/accountmanager.cpp

@@ -30,6 +30,7 @@ static const char httpUserC[] = "http_user";
 static const char caCertsKeyC[] = "CaCertificates";
 static const char accountsC[] = "Accounts";
 static const char versionC[] = "version";
+static const char serverVersionC[] = "serverVersion";
 }
 
 
@@ -165,6 +166,7 @@ void AccountManager::saveAccountState(AccountState* a)
 void AccountManager::saveAccountHelper(Account* acc, QSettings& settings, bool saveCredentials)
 {
     settings.setValue(QLatin1String(urlC), acc->_url.toString());
+    settings.setValue(QLatin1String(serverVersionC), acc->_serverVersion);
     if (acc->_credentials) {
         if (saveCredentials) {
             // Only persist the credentials if the parameter is set, on migration from 1.8.x
@@ -210,6 +212,7 @@ AccountPtr AccountManager::loadAccountHelper(QSettings& settings)
     auto acc = createAccount();
 
     acc->setUrl(settings.value(QLatin1String(urlC)).toUrl());
+    acc->_serverVersion = settings.value(QLatin1String(serverVersionC)).toString();
 
     // We want to only restore settings for that auth type and the user value
     acc->_settingsMap.insert(QLatin1String(userC), settings.value(userC));

src/gui/accountsettings.cpp

@@ -512,7 +512,11 @@ void AccountSettings::slotAccountStateChanged(int state)
         }
 
         if (state == AccountState::Connected) {
-            showConnectionLabel( tr("Connected to %1.").arg(serverWithUser) );
+            QStringList errors;
+            if (account->serverVersionUnsupported()) {
+                errors << tr("The server version %1 is old and unsupported! Proceed at your own risk.").arg(account->serverVersion());
+            }
+            showConnectionLabel( tr("Connected to %1.").arg(serverWithUser), errors );
         } else if (state == AccountState::ServiceUnavailable) {
             showConnectionLabel( tr("Server %1 is temporarily unavailable.").arg(server) );
         } else if (state == AccountState::SignedOut) {

src/gui/application.cpp

@@ -219,10 +219,14 @@ void Application::slotAccountStateRemoved(AccountState *accountState)
     if (_gui) {
         disconnect(accountState, SIGNAL(stateChanged(int)),
                    _gui, SLOT(slotAccountStateChanged()));
+        disconnect(accountState->account().data(), SIGNAL(serverVersionChanged(Account*,QString,QString)),
+                   _gui, SLOT(slotTrayMessageIfServerUnsupported(Account*)));
     }
     if (_folderManager) {
         disconnect(accountState, SIGNAL(stateChanged(int)),
                    _folderManager.data(), SLOT(slotAccountStateChanged()));
+        disconnect(accountState->account().data(), SIGNAL(serverVersionChanged(Account*,QString,QString)),
+                   _folderManager.data(), SLOT(slotServerVersionChanged(Account*)));
     }
 
     // if there is no more account, show the wizard.
@@ -237,8 +241,14 @@ void Application::slotAccountStateAdded(AccountState *accountState)
 {
     connect(accountState, SIGNAL(stateChanged(int)),
             _gui, SLOT(slotAccountStateChanged()));
+    connect(accountState->account().data(), SIGNAL(serverVersionChanged(Account*,QString,QString)),
+            _gui, SLOT(slotTrayMessageIfServerUnsupported(Account*)));
     connect(accountState, SIGNAL(stateChanged(int)),
             _folderManager.data(), SLOT(slotAccountStateChanged()));
+    connect(accountState->account().data(), SIGNAL(serverVersionChanged(Account*,QString,QString)),
+            _folderManager.data(), SLOT(slotServerVersionChanged(Account*)));
+
+    _gui->slotTrayMessageIfServerUnsupported(accountState->account().data());
 }
 
 void Application::slotCleanup()

src/gui/folderman.cpp

@@ -744,6 +744,21 @@ void FolderMan::slotForwardFolderSyncStateChange()
     }
 }
 
+void FolderMan::slotServerVersionChanged(Account *account)
+{
+    // Pause folders if the server version is unsupported
+    if (account->serverVersionUnsupported()) {
+        qDebug() << "The server version is unsupported:" << account->serverVersion()
+                 << "pausing all folders on the account";
+
+        foreach (auto& f, _folderMap) {
+            if (f->accountState()->account().data() == account) {
+                f->setSyncPaused(true);
+            }
+        }
+    }
+}
+
 void FolderMan::slotFolderSyncStarted( )
 {
     qDebug() << ">===================================== sync started for " << _currentSyncFolder->remoteUrl().toString();

src/gui/folderman.h

@@ -196,6 +196,8 @@ private slots:
     // FolderMan::folderSyncStateChange(Folder*) signal.
     void slotForwardFolderSyncStateChange();
 
+    void slotServerVersionChanged(Account* account);
+
 private:
     /** Adds a new folder, does not add it to the account settings and
      *  does not set an account on the new folder.

src/gui/owncloudgui.cpp

@@ -228,6 +228,18 @@ void ownCloudGui::slotAccountStateChanged()
     slotComputeOverallSyncStatus();
 }
 
+void ownCloudGui::slotTrayMessageIfServerUnsupported(Account* account)
+{
+    if (account->serverVersionUnsupported()) {
+        slotShowTrayMessage(
+                tr("Unsupported Server Version"),
+                tr("The server on account %1 runs an old and unsupported version %2. "
+                   "Using this client with unsupported server versions is untested and "
+                   "potentially dangerous. Proceed at your own risk.")
+                    .arg(account->displayName(), account->serverVersion()));
+    }
+}
+
 void ownCloudGui::slotComputeOverallSyncStatus()
 {
     bool allSignedOut = true;

src/gui/owncloudgui.h

@@ -77,6 +77,7 @@ public slots:
     void slotHelp();
     void slotOpenPath(const QString& path);
     void slotAccountStateChanged();
+    void slotTrayMessageIfServerUnsupported(Account *account);
     void slotShowShareDialog(const QString &sharePath, const QString &localPath, bool resharingAllowed);
     void slotRemoveDestroyedShareDialogs();
 

src/libsync/account.cpp

@@ -472,23 +472,34 @@ void Account::setCapabilities(const QVariantMap &caps)
     _capabilities = Capabilities(caps);
 }
 
-QString Account::serverVersion()
+QString Account::serverVersion() const
 {
     return _serverVersion;
 }
 
-int Account::serverVersionInt()
+int Account::serverVersionInt() const
 {
     // FIXME: Use Qt 5.5 QVersionNumber
     auto components = serverVersion().split('.');
     return  (components.value(0).toInt() << 16)
                    + (components.value(1).toInt() << 8)
-                   + components.value(2).toInt();
+            + components.value(2).toInt();
+}
+
+bool Account::serverVersionUnsupported() const
+{
+    return serverVersionInt() < 0x070000;
 }
 
 void Account::setServerVersion(const QString& version)
 {
+    if (version == _serverVersion) {
+        return;
+    }
+
+    auto oldServerVersion = _serverVersion;
     _serverVersion = version;
+    emit serverVersionChanged(this, oldServerVersion, version);
 }
 
 bool Account::rootEtagChangesNotOnlySubFolderEtags()

src/libsync/account.h

@@ -154,8 +154,20 @@ class OWNCLOUDSYNC_EXPORT Account : public QObject {
     void setCapabilities(const QVariantMap &caps);
     const Capabilities &capabilities() const;
     void setServerVersion(const QString &version);
-    QString serverVersion();
-    int serverVersionInt();
+    QString serverVersion() const;
+    int serverVersionInt() const;
+
+    /** Whether the server is too old.
+     *
+     * Not supporting server versions is a gradual process. There's a hard
+     * compatibility limit (see ConnectionValidator) that forbids connecting
+     * to extremely old servers. And there's a weak "untested, not
+     * recommended, potentially dangerous" limit, that users might want
+     * to go beyond.
+     *
+     * This function returns true if the server is beyond the weak limit.
+     */
+    bool serverVersionUnsupported() const;
 
     // Fixed from 8.1 https://github.com/owncloud/client/issues/3730
     bool rootEtagChangesNotOnlySubFolderEtags();
@@ -181,6 +193,8 @@ class OWNCLOUDSYNC_EXPORT Account : public QObject {
     // e.g. when the approved SSL certificates changed
     void wantsAccountSaved(Account* acc);
 
+    void serverVersionChanged(Account* account, const QString& newVersion, const QString& oldVersion);
+
 protected Q_SLOTS:
     void slotHandleSslErrors(QNetworkReply*,QList<QSslError>);
     void slotCredentialsFetched();

src/libsync/connectionvalidator.cpp

@@ -122,13 +122,17 @@ void ConnectionValidator::slotStatusFound(const QUrl&url, const QVariantMap &inf
     QString version = CheckServerJob::version(info);
     _account->setServerVersion(version);
 
+    // We cannot deal with servers < 5.0.0
     if (version.contains('.') && version.split('.')[0].toInt() < 5) {
         _errors.append( tr("The configured server for this client is too old") );
         _errors.append( tr("Please update to the latest server and restart the client.") );
         reportResult( ServerVersionMismatch );
         return;
     }
 
+    // We attempt to work with servers >= 5.0.0 but warn users.
+    // Check usages of Account::serverVersionUnsupported() for details.
+
     // now check the authentication
     if (_account->credentials()->ready())
         QTimer::singleShot( 0, this, SLOT( checkAuthentication() ));