Some refactoring

  - Add reportSessionCrash to Session, for reporting crashes to user
  - Use reportSessionCrash in PythonSession and improve login of PythonSession::logout()

src/backends/python/pythonsession.cpp

@@ -116,7 +116,8 @@ void PythonSession::logout()
     if (!m_process)
         return;
 
-    sendCommand(QLatin1String("exit"));
+    if (m_process->exitStatus() != QProcess::CrashExit && m_process->error() != QProcess::WriteError)
+        sendCommand(QLatin1String("exit"));
     if(m_process->state() == QProcess::Running && !m_process->waitForFinished(1000))
     {
         disconnect(m_process, &QProcess::errorOccurred, this, &PythonSession::reportServerProcessError);
@@ -275,8 +276,5 @@ void PythonSession::reportServerProcessError(QProcess::ProcessError serverError)
             emit error(i18n("Communication with Cantor python server failed for unknown reasons."));
             break;
     }
-    // Server crash, and now m_process is invalid, so remove m_process object
-    m_process->deleteLater();
-    m_process = nullptr;
-    Session::logout();
+    reportSessionCrash();
 }

src/lib/session.cpp

@@ -26,6 +26,8 @@ using namespace Cantor;
 
 #include <QTimer>
 #include <QQueue>
+#include <KMessageBox>
+#include <KLocalizedString>
 
 class Cantor::SessionPrivate
 {
@@ -181,10 +183,9 @@ QSyntaxHighlighter* Session::syntaxHighlighter(QObject* parent)
 
 DefaultVariableModel* Session::variableModel() const
 {
-    //Return deafult session model per default
-    //By default, variableModel is nullptr, so Backends not offering variable management don't
-    //have to reimplement this. This method should only be called on backends with
-    //VariableManagement Capability flag
+    //By default, there is variableModel in session, used by syntax higlighter for variable analyzing
+    //The model store only variable names by default.
+    //In backends with VariableManagement Capability flag, this model also used for Cantor variable doc panel
     return d->variableModel;
 }
 
@@ -231,3 +232,16 @@ QStringList Session::locateAllCantorFiles(const QString& partialPath, QStandardP
 
     return files;
 }
+
+void Cantor::Session::reportSessionCrash(const QString& additionalInfo)
+{
+    // Reporting about crashing backend in session without backend has not sense
+    if (d->backend == nullptr)
+        return;
+
+    if (additionalInfo.isEmpty())
+        KMessageBox::error(nullptr, i18n("%1 process has died unexpectedly. All calculation results are lost.", d->backend->name()), i18n("Error - Cantor"));
+    else
+        KMessageBox::error(nullptr, i18n("%1 process has died unexpectedly with message \"%2\". All calculation results are lost.", d->backend->name()), i18n("Error - Cantor"));
+    logout();
+}

src/lib/session.h

@@ -251,6 +251,15 @@ class CANTOR_EXPORT Session : public QObject
     QString locateCantorFile(const QString& partialPath, QStandardPaths::LocateOptions options = QStandardPaths::LocateFile);
     QStringList locateAllCantorFiles(const QString& partialPath, QStandardPaths::LocateOptions options = QStandardPaths::LocateFile);
 
+    /**
+     * Sometimes backend process/server could crash, stop responding, in other words, session can't
+     * continue to work without restart.
+     * This method will notify about session crashing with automatically logout
+     * and another actions, which needed to do in situations like that
+     */
+    void reportSessionCrash(const QString& additionalInfo = QString());
+
+
 Q_SIGNALS:
     void statusChanged(Cantor::Session::Status newStatus);
     void loginStarted();