Don't silently close QGIS with unsaved changes in the console script

python/console/console.py

@@ -23,14 +23,23 @@
 from qgis.PyQt.QtCore import Qt, QTimer, QCoreApplication, QSize, QByteArray, QFileInfo, QUrl, QDir
 from qgis.PyQt.QtWidgets import QToolBar, QToolButton, QWidget, QSplitter, QTreeWidget, QAction, QFileDialog, QCheckBox, QSizePolicy, QMenu, QGridLayout, QApplication, QShortcut
 from qgis.PyQt.QtGui import QDesktopServices, QKeySequence
-from qgis.PyQt.QtWidgets import QVBoxLayout
+from qgis.PyQt.QtWidgets import (
+    QVBoxLayout,
+    QMessageBox
+)
 from qgis.utils import iface
 from .console_sci import ShellScintilla
 from .console_output import ShellOutputScintilla
 from .console_editor import EditorTabWidget
 from .console_settings import ConsoleOptionsFactory
 from qgis.core import Qgis, QgsApplication, QgsSettings
-from qgis.gui import QgsFilterLineEdit, QgsHelp, QgsDockWidget, QgsGui
+from qgis.gui import (
+    QgsFilterLineEdit,
+    QgsHelp,
+    QgsDockWidget,
+    QgsGui,
+    QgsApplicationExitBlockerInterface
+)
 from functools import partial
 
 import sys
@@ -80,6 +89,16 @@ def init_options_widget():
     iface.registerOptionsWidgetFactory(_options_factory)
 
 
+class ConsoleExitBlocker(QgsApplicationExitBlockerInterface):
+
+    def __init__(self, console):
+        super().__init__()
+        self.console = console
+
+    def allowExit(self):
+        return self.console.allowExit()
+
+
 class PythonConsole(QgsDockWidget):
 
     def __init__(self, parent=None):
@@ -543,6 +562,34 @@ def __init__(self, parent=None):
         self.findScut.setContext(Qt.WidgetWithChildrenShortcut)
         self.findScut.activated.connect(self._closeFind)
 
+        if iface is not None:
+            self.exit_blocker = ConsoleExitBlocker(self)
+            iface.registerApplicationExitBlocker(self.exit_blocker)
+
+    def allowExit(self):
+        tab_count = self.tabEditorWidget.count()
+        for i in range(tab_count):
+            # iterate backwards through tabs, as we may be closing some as we go
+            tab_index = tab_count - i - 1
+            tab_widget = self.tabEditorWidget.widget(tab_index)
+            if tab_widget.newEditor.isModified():
+                ret = QMessageBox.question(self, self.tr("Save {}").format(self.tabEditorWidget.tabText(tab_index)),
+                                           self.tr("There are unsaved changes in this script. Do you want to keep those?"),
+                                           QMessageBox.Save | QMessageBox.Cancel | QMessageBox.Discard, QMessageBox.Cancel)
+                if ret == QMessageBox.Save:
+                    tab_widget.save()
+                    if tab_widget.newEditor.isModified():
+                        # save failed, treat as cancel
+                        return False
+                elif ret == QMessageBox.Discard:
+                    pass
+                else:
+                    return False
+
+            self.tabEditorWidget.removeTab(tab_index)
+
+        return True
+
     def _toggleFind(self):
         self.tabEditorWidget.currentWidget().newEditor.toggleFindWidget()
 

python/gui/auto_generated/qgisinterface.sip.in

@@ -1234,6 +1234,30 @@ Unregister a previously registered tool factory from the development/debugging t
 .. seealso:: :py:func:`registerDevToolWidgetFactory`
 
 .. versionadded:: 3.14
+%End
+
+    virtual void registerApplicationExitBlocker( QgsApplicationExitBlockerInterface *blocker ) = 0;
+%Docstring
+Register a new application exit blocker, which can be used to prevent the QGIS application
+from exiting while a plugin or script has unsaved changes.
+
+.. note::
+
+   Ownership of ``blocker`` is not transferred, and the blocker must
+   be unregistered when plugin is unloaded.
+
+.. seealso:: :py:func:`unregisterApplicationExitBlocker`
+
+.. versionadded:: 3.16
+%End
+
+    virtual void unregisterApplicationExitBlocker( QgsApplicationExitBlockerInterface *blocker ) = 0;
+%Docstring
+Unregister a previously registered application exit ``blocker``.
+
+.. seealso:: :py:func:`registerApplicationExitBlocker`
+
+.. versionadded:: 3.16
 %End
 
     virtual void registerCustomDropHandler( QgsCustomDropHandler *handler ) = 0;

python/gui/auto_generated/qgsapplicationexitblockerinterface.sip.in

@@ -0,0 +1,77 @@
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/gui/qgsapplicationexitblockerinterface.h                         *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
+
+
+
+class QgsApplicationExitBlockerInterface
+{
+%Docstring
+An interface that may be implemented to allow plugins or scripts to temporarily block
+the QGIS application from exiting.
+
+This interface allows plugins to implement custom logic to determine whether it is safe
+for the application to exit, e.g. by checking whether the plugin or script has any
+unsaved changes which should be saved or discarded before allowing QGIS to exit.
+
+QgsApplicationExitBlockerInterface are registered via the iface object:
+
+Example
+-------
+
+.. code-block:: python
+
+       class MyPluginExitBlocker(QgsApplicationExitBlockerInterface):
+
+          def allowExit(self):
+              if self.has_unsaved_changes():
+                  # show a warning prompt
+                  # ...
+                  # prevent QGIS application from exiting
+                  return False
+
+              # allow QGIS application to exit
+              return True
+
+       my_blocker = MyPluginExitBlocker()
+       iface.registerApplicationExitBlocker(my_blocker)
+
+.. versionadded:: 3.16
+%End
+
+%TypeHeaderCode
+#include "qgsapplicationexitblockerinterface.h"
+%End
+  public:
+
+    virtual ~QgsApplicationExitBlockerInterface();
+
+    virtual bool allowExit() = 0;
+%Docstring
+Called whenever the QGIS application has been asked to exit by a user.
+
+The subclass can use this method to implement custom logic handling whether it is safe
+for the application to exit, e.g. by checking whether the plugin or script has any unsaved
+changes which should be saved or discarded before allowing QGIS to exit.
+
+The implementation should return ``True`` if it is safe for QGIS to exit, or ``False`` if it
+wishes to prevent the application from exiting.
+
+.. note::
+
+   It is safe to use GUI widgets in implementations of this function, including message
+   boxes or custom dialogs with event loops.
+%End
+};
+
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/gui/qgsapplicationexitblockerinterface.h                         *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/

python/gui/gui_auto.sip

@@ -7,6 +7,7 @@
 %Include auto_generated/qgsadvanceddigitizingfloater.sip
 %Include auto_generated/qgsaggregatetoolbutton.sip
 %Include auto_generated/qgsalignmentcombobox.sip
+%Include auto_generated/qgsapplicationexitblockerinterface.sip
 %Include auto_generated/qgsattributedialog.sip
 %Include auto_generated/qgsattributeeditorcontext.sip
 %Include auto_generated/qgsattributeform.sip

src/app/qgisapp.cpp

@@ -181,6 +181,7 @@ Q_GUI_EXPORT extern int qt_defaultDpiX();
 #include "qgsauthsslerrorsdialog.h"
 #endif
 #include "qgsappscreenshots.h"
+#include "qgsapplicationexitblockerinterface.h"
 #include "qgsbookmarks.h"
 #include "qgsbookmarkeditordialog.h"
 #include "qgsbrowserdockwidget.h"
@@ -6388,7 +6389,7 @@ void QgisApp::fileExit()
   }
 
   QgsCanvasRefreshBlocker refreshBlocker;
-  if ( checkUnsavedLayerEdits() && checkMemoryLayers() && saveDirty() )
+  if ( checkUnsavedLayerEdits() && checkMemoryLayers() && checkExitBlockers() && saveDirty() )
   {
     closeProject();
     userProfileManager()->setDefaultFromActive();
@@ -12686,6 +12687,16 @@ void QgisApp::unregisterDevToolFactory( QgsDevToolWidgetFactory *factory )
   mDevToolFactories.removeAll( factory );
 }
 
+void QgisApp::registerApplicationExitBlocker( QgsApplicationExitBlockerInterface *blocker )
+{
+  mApplicationExitBlockers << blocker;
+}
+
+void QgisApp::unregisterApplicationExitBlocker( QgsApplicationExitBlockerInterface *blocker )
+{
+  mApplicationExitBlockers.removeAll( blocker );
+}
+
 QgsMapLayer *QgisApp::activeLayer()
 {
   return mLayerTreeView ? mLayerTreeView->currentLayer() : nullptr;
@@ -13237,6 +13248,16 @@ bool QgisApp::checkMemoryLayers()
   return close;
 }
 
+bool QgisApp::checkExitBlockers()
+{
+  for ( QgsApplicationExitBlockerInterface *blocker : qgis::as_const( mApplicationExitBlockers ) )
+  {
+    if ( !blocker->allowExit() )
+      return false;
+  }
+  return true;
+}
+
 bool QgisApp::checkTasksDependOnProject()
 {
   QSet< QString > activeTaskDescriptions;

src/app/qgisapp.h

@@ -111,6 +111,7 @@ class Qgs3DMapCanvasDockWidget;
 class QgsHandleBadLayersHandler;
 class QgsNetworkAccessManager;
 class QgsGpsConnection;
+class QgsApplicationExitBlockerInterface;
 
 class QDomDocument;
 class QNetworkReply;
@@ -746,6 +747,23 @@ class APP_EXPORT QgisApp : public QMainWindow, private Ui::MainWindow
     //! Unregister a previously registered dev tool factory
     void unregisterDevToolFactory( QgsDevToolWidgetFactory *factory );
 
+    /**
+     * Register a new application exit blocker, which can be used to prevent the QGIS application
+     * from exiting while a plugin or script has unsaved changes.
+     *
+     * \note Ownership of \a blocker is not transferred, and the blocker must
+     *       be unregistered when plugin is unloaded.
+     *
+     * \see unregisterApplicationExitBlocker()
+     */
+    void registerApplicationExitBlocker( QgsApplicationExitBlockerInterface *blocker );
+
+    /**
+     * Unregister a previously registered application exit \a blocker.
+     * \see registerApplicationExitBlocker()
+    */
+    void unregisterApplicationExitBlocker( QgsApplicationExitBlockerInterface *blocker );
+
     //! Register a new custom drop handler.
     void registerCustomDropHandler( QgsCustomDropHandler *handler );
 
@@ -2094,6 +2112,12 @@ class APP_EXPORT QgisApp : public QMainWindow, private Ui::MainWindow
      */
     bool checkMemoryLayers();
 
+    /**
+     * Checks whether any registered application exit blockers should prevent
+     * the application from exiting.
+     */
+    bool checkExitBlockers();
+
     //! Checks for running tasks dependent on the open project
     bool checkTasksDependOnProject();
 
@@ -2569,6 +2593,8 @@ class APP_EXPORT QgisApp : public QMainWindow, private Ui::MainWindow
 
     QList<QgsDevToolWidgetFactory * > mDevToolFactories;
 
+    QList<QgsApplicationExitBlockerInterface * > mApplicationExitBlockers;
+
     QVector<QPointer<QgsCustomDropHandler>> mCustomDropHandlers;
     QVector<QPointer<QgsCustomProjectOpenHandler>> mCustomProjectOpenHandlers;
     QVector<QPointer<QgsLayoutCustomDropHandler>> mCustomLayoutDropHandlers;

src/app/qgisappinterface.cpp

@@ -571,6 +571,16 @@ void QgisAppInterface::unregisterDevToolWidgetFactory( QgsDevToolWidgetFactory *
   qgis->unregisterDevToolFactory( factory );
 }
 
+void QgisAppInterface::registerApplicationExitBlocker( QgsApplicationExitBlockerInterface *blocker )
+{
+  qgis->registerApplicationExitBlocker( blocker );
+}
+
+void QgisAppInterface::unregisterApplicationExitBlocker( QgsApplicationExitBlockerInterface *blocker )
+{
+  qgis->unregisterApplicationExitBlocker( blocker );
+}
+
 void QgisAppInterface::registerCustomDropHandler( QgsCustomDropHandler *handler )
 {
   qgis->registerCustomDropHandler( handler );

src/app/qgisappinterface.h

@@ -150,6 +150,8 @@ class APP_EXPORT QgisAppInterface : public QgisInterface
     void unregisterProjectPropertiesWidgetFactory( QgsOptionsWidgetFactory *factory ) override;
     void registerDevToolWidgetFactory( QgsDevToolWidgetFactory *factory ) override;
     void unregisterDevToolWidgetFactory( QgsDevToolWidgetFactory *factory ) override;
+    void registerApplicationExitBlocker( QgsApplicationExitBlockerInterface *blocker ) override;
+    void unregisterApplicationExitBlocker( QgsApplicationExitBlockerInterface *blocker ) override;
     void registerCustomDropHandler( QgsCustomDropHandler *handler ) override;
     void unregisterCustomDropHandler( QgsCustomDropHandler *handler ) override;
     void registerCustomProjectOpenHandler( QgsCustomProjectOpenHandler *handler ) override;

src/gui/CMakeLists.txt

@@ -592,6 +592,7 @@ SET(QGIS_GUI_HDRS
   qgsadvanceddigitizingfloater.h
   qgsaggregatetoolbutton.h
   qgsalignmentcombobox.h
+  qgsapplicationexitblockerinterface.h
   qgsattributedialog.h
   qgsattributeeditorcontext.h
   qgsattributeform.h

src/gui/qgisinterface.h

@@ -65,6 +65,7 @@ class QgsMeshLayer;
 class QgsBrowserGuiModel;
 class QgsDevToolWidgetFactory;
 class QgsGpsConnection;
+class QgsApplicationExitBlockerInterface;
 
 
 /**
@@ -1025,6 +1026,25 @@ class GUI_EXPORT QgisInterface : public QObject
     */
     virtual void unregisterDevToolWidgetFactory( QgsDevToolWidgetFactory *factory ) = 0;
 
+    /**
+     * Register a new application exit blocker, which can be used to prevent the QGIS application
+     * from exiting while a plugin or script has unsaved changes.
+     *
+     * \note Ownership of \a blocker is not transferred, and the blocker must
+     *       be unregistered when plugin is unloaded.
+     *
+     * \see unregisterApplicationExitBlocker()
+     * \since QGIS 3.16
+     */
+    virtual void registerApplicationExitBlocker( QgsApplicationExitBlockerInterface *blocker ) = 0;
+
+    /**
+     * Unregister a previously registered application exit \a blocker.
+     * \see registerApplicationExitBlocker()
+     * \since QGIS 3.16
+    */
+    virtual void unregisterApplicationExitBlocker( QgsApplicationExitBlockerInterface *blocker ) = 0;
+
     /**
      * Register a new custom drop \a handler.
      * \note Ownership of \a handler is not transferred, and the handler must