[browser] Fix crash when deleting files quickly

It's possible for items to be deleted in the background
while we are waiting on user input (e.g. from the confirmation
prompt) by a parent directory refresh, so we need to capture
everything relevant and not rely on the item itself existing
anymore during the delete layer calls.

Author: nyalldawson

src/core/qgsdataitem.h

@@ -322,7 +322,7 @@ class CORE_EXPORT QgsDataItem : public QObject
 
     Type mType;
     Capabilities mCapabilities;
-    QPointer< QgsDataItem > mParent;
+    QgsDataItem *mParent = nullptr;
     QVector<QgsDataItem *> mChildren; // easier to have it always
     State mState;
     QString mName;

src/providers/gdal/qgsgdaldataitems.cpp

@@ -126,53 +126,65 @@ QString QgsGdalLayerItem::layerName() const
 #ifdef HAVE_GUI
 QList<QAction *> QgsGdalLayerItem::actions( QWidget *parent )
 {
-  QList<QAction *> lst;
+  QList<QAction *> lst = QgsLayerItem::actions( parent );
+
   // Messages are different for files and tables
   const QString message = QObject::tr( "Delete File “%1”…" ).arg( mName );
   QAction *actionDeleteLayer = new QAction( message, parent );
-  connect( actionDeleteLayer, &QAction::triggered, this, &QgsGdalLayerItem::deleteLayer );
+
+  // IMPORTANT - we need to capture the stuff we need, and then hand the slot
+  // off to a static method. This is because it's possible for this item
+  // to be deleted in the background on us (e.g. by a parent directory refresh)
+  const QString uri = mUri;
+  const QString path = mPath;
+  QPointer< QgsDataItem > parentItem( mParent );
+  connect( actionDeleteLayer, &QAction::triggered, this, [ uri, path, parentItem ]
+  {
+    deleteLayer( uri, path, parentItem );
+  } );
+
   lst.append( actionDeleteLayer );
   return lst;
 }
 
-void QgsGdalLayerItem::deleteLayer()
+void QgsGdalLayerItem::deleteLayer( const QString &uri, const QString &path, QPointer< QgsDataItem > parent )
 {
   const QString title = QObject::tr( "Delete File" );
   // Check if the layer is in the project
   const QgsMapLayer *projectLayer = nullptr;
   const auto mapLayers = QgsProject::instance()->mapLayers();
   for ( auto it = mapLayers.constBegin(); it != mapLayers.constEnd(); ++it )
   {
-    if ( it.value()->publicSource() == mUri )
+    if ( it.value()->publicSource() == uri )
     {
       projectLayer = it.value();
     }
   }
   if ( ! projectLayer )
   {
-    const QString confirmMessage = QObject::tr( "Are you sure you want to delete file '%1'?" ).arg( mPath );
+    const QString confirmMessage = QObject::tr( "Are you sure you want to delete file '%1'?" ).arg( path );
 
     if ( QMessageBox::question( nullptr, title,
                                 confirmMessage,
                                 QMessageBox::Yes | QMessageBox::No, QMessageBox::No ) != QMessageBox::Yes )
       return;
 
 
-    if ( !QFile::remove( mPath ) )
+    if ( !QFile::remove( path ) )
     {
       QMessageBox::warning( nullptr, title, tr( "Could not delete file." ) );
     }
     else
     {
       QMessageBox::information( nullptr, title, tr( "File deleted successfully." ) );
-      if ( mParent )
-        mParent->refresh();
+      if ( parent )
+        parent->refresh();
     }
   }
   else
   {
     QMessageBox::warning( nullptr, title, QObject::tr( "The layer '%1' cannot be deleted because it is in the current project as '%2',"
-                          " remove it from the project and retry." ).arg( mName, projectLayer->name() ) );
+                          " remove it from the project and retry." ).arg( path, projectLayer->name() ) );
   }
 }
 #endif

src/providers/gdal/qgsgdaldataitems.h

@@ -40,8 +40,9 @@ class QgsGdalLayerItem : public QgsLayerItem
 
 #ifdef HAVE_GUI
     QList<QAction *> actions( QWidget *parent ) override;
-  public slots:
-    void deleteLayer();
+
+    static void deleteLayer( const QString &uri, const QString &path, QPointer< QgsDataItem > parent );
+
 #endif
 };
 

src/providers/ogr/qgsogrdataitems.cpp

@@ -309,61 +309,73 @@ QString QgsOgrLayerItem::layerName() const
 #ifdef HAVE_GUI
 QList<QAction *> QgsOgrLayerItem::actions( QWidget *parent )
 {
-  QList<QAction *> lst;
+  QList<QAction *> lst = QgsLayerItem::actions( parent );
+
   // Messages are different for files and tables
   QString message = mIsSubLayer ? QObject::tr( "Delete Layer “%1”…" ).arg( mName ) : QObject::tr( "Delete File “%1”…" ).arg( mName );
   QAction *actionDeleteLayer = new QAction( message, parent );
-  connect( actionDeleteLayer, &QAction::triggered, this, &QgsOgrLayerItem::deleteLayer );
+
+  // IMPORTANT - we need to capture the stuff we need, and then hand the slot
+  // off to a static method. This is because it's possible for this item
+  // to be deleted in the background on us (e.g. by a parent directory refresh)
+  const bool isSubLayer = mIsSubLayer;
+  const QString uri = mUri;
+  const QString name = mName;
+  QPointer< QgsDataItem > parentItem( mParent );
+  connect( actionDeleteLayer, &QAction::triggered, this, [ isSubLayer, uri, name, parentItem ]
+  {
+    deleteLayer( isSubLayer, uri, name, parentItem );
+  } );
   lst.append( actionDeleteLayer );
   return lst;
 }
 
-void QgsOgrLayerItem::deleteLayer()
+void QgsOgrLayerItem::deleteLayer( const bool isSubLayer, const QString &uri, const QString &name, QPointer< QgsDataItem > parent )
 {
   // Messages are different for files and tables
-  QString title = mIsSubLayer ? QObject::tr( "Delete Layer" ) : QObject::tr( "Delete File" );
+  QString title = isSubLayer ? QObject::tr( "Delete Layer" ) : QObject::tr( "Delete File" );
   // Check if the layer is in the registry
   const QgsMapLayer *projectLayer = nullptr;
   Q_FOREACH ( const QgsMapLayer *layer, QgsProject::instance()->mapLayers() )
   {
-    if ( layer->publicSource() == mUri )
+    if ( layer->publicSource() == uri )
     {
       projectLayer = layer;
     }
   }
   if ( ! projectLayer )
   {
     QString confirmMessage;
-    if ( mIsSubLayer )
+    if ( isSubLayer )
     {
-      confirmMessage = QObject::tr( "Are you sure you want to delete layer '%1' from datasource?" ).arg( mName );
+      confirmMessage = QObject::tr( "Are you sure you want to delete layer '%1' from datasource?" ).arg( name );
     }
     else
     {
-      confirmMessage = QObject::tr( "Are you sure you want to delete file '%1'?" ).arg( mUri );
+      confirmMessage = QObject::tr( "Are you sure you want to delete file '%1'?" ).arg( uri );
     }
     if ( QMessageBox::question( nullptr, title,
                                 confirmMessage,
                                 QMessageBox::Yes | QMessageBox::No, QMessageBox::No ) != QMessageBox::Yes )
       return;
 
     QString errCause;
-    bool res = ::deleteLayer( mUri, errCause );
+    bool res = ::deleteLayer( uri, errCause );
     if ( !res )
     {
       QMessageBox::warning( nullptr, title, errCause );
     }
     else
     {
-      QMessageBox::information( nullptr, title, mIsSubLayer ? tr( "Layer deleted successfully." ) :  tr( "File deleted successfully." ) );
-      if ( mParent )
-        mParent->refresh();
+      QMessageBox::information( nullptr, title, isSubLayer ? tr( "Layer deleted successfully." ) :  tr( "File deleted successfully." ) );
+      if ( parent )
+        parent->refresh();
     }
   }
   else
   {
     QMessageBox::warning( nullptr, title, QObject::tr( "The layer '%1' cannot be deleted because it is in the current project as '%2',"
-                          " remove it from the project and retry." ).arg( mName, projectLayer->name() ) );
+                          " remove it from the project and retry." ).arg( name, projectLayer->name() ) );
   }
 }
 #endif

src/providers/ogr/qgsogrdataitems.h

@@ -69,8 +69,8 @@ class QgsOgrLayerItem : public QgsLayerItem
 
 #ifdef HAVE_GUI
     QList<QAction *> actions( QWidget *parent ) override;
-  public slots:
-    void deleteLayer();
+
+    static void deleteLayer( bool isSubLayer, const QString &uri, const QString &name, QPointer< QgsDataItem > parent );
 #endif
   private:
     bool mIsSubLayer;