Merge pull request #52450 from m-kuhn/bp51456

Manual backport of 51456 merge feature relocation

python/core/auto_generated/vector/qgsvectorlayereditutils.sip.in

@@ -310,6 +310,21 @@ editing.
 :return: 2 in case vertex already exists or point does not intersect segment
 
 .. versionadded:: 3.16
+%End
+
+    bool mergeFeatures( const QgsFeatureId &targetFeatureId, const QgsFeatureIds &mergeFeatureIds, const QgsAttributes &mergeAttributes, const QgsGeometry &unionGeometry, QString &errorMessage /Out/ );
+%Docstring
+Merge features into a single one.
+
+:param targetFeatureId: id of the target feature (will be updated)
+:param mergeFeatureIds: id list of features to merge (will be deleted)
+:param mergeAttributes: are the resulting attributes in the merged feature
+:param unionGeometry: is the resulting geometry of the merged feature
+
+:return: - ``True`` if the merge was successful, or ``False`` if the operation failed.
+         - errorMessage: will be set to a descriptive error message if any occurs
+
+.. versionadded:: 3.30
 %End
 
 };

src/app/qgisapp.cpp

@@ -102,6 +102,7 @@
 #include "qgsdockablewidgethelper.h"
 #include "vertextool/qgsvertexeditor.h"
 #include "qgsvectorlayerutils.h"
+#include "qgsvectorlayereditutils.h"
 #include "qgsadvanceddigitizingdockwidget.h"
 #include "qgsabstractdatasourcewidget.h"
 #include "qgsmeshlayer.h"
@@ -9517,9 +9518,8 @@ void QgisApp::mergeSelectedFeatures()
     return;
   }
 
-  //get selected feature ids (as a QSet<int> )
-  const QgsFeatureIds &featureIdSet = vl->selectedFeatureIds();
-  if ( featureIdSet.size() < 2 )
+  // Check at least two features are selected
+  if ( vl->selectedFeatureIds().size() < 2 )
   {
     visibleMessageBar()->pushMessage(
       tr( "Not enough features selected" ),
@@ -9593,73 +9593,38 @@ void QgisApp::mergeSelectedFeatures()
       }
       return;
     }
-  }
-
-  QgsAttributes attrs = d.mergedAttributes();
-  QgsAttributeMap newAttributes;
-  QString errorMessage;
-  QgsFeatureId mergeFeatureId = FID_NULL;
-  for ( int i = 0; i < attrs.count(); ++i )
-  {
-    QVariant val = attrs.at( i );
-    bool isDefaultValue = vl->fields().fieldOrigin( i ) == QgsFields::OriginProvider &&
-                          vl->dataProvider() &&
-                          vl->dataProvider()->defaultValueClause( vl->fields().fieldOriginIndex( i ) ) == val;
-    bool isPrimaryKey =  vl->fields().fieldOrigin( i ) == QgsFields::OriginProvider &&
-                         vl->dataProvider() &&
-                         vl->dataProvider()->pkAttributeIndexes().contains( vl->fields().fieldOriginIndex( i ) );
-
-    if ( isPrimaryKey && !isDefaultValue )
-      mergeFeatureId = val.toLongLong();
-
-    // convert to destination data type
-    if ( !isDefaultValue && !vl->fields().at( i ).convertCompatible( val, &errorMessage ) )
+    else if ( !QgsWkbTypes::isMultiType( vl->wkbType() ) )
     {
-      visibleMessageBar()->pushMessage(
-        tr( "Invalid result" ),
-        tr( "Could not store value '%1' in field of type %2: %3" ).arg( attrs.at( i ).toString(), vl->fields().at( i ).typeName(), errorMessage ),
-        Qgis::MessageLevel::Warning );
+      const QgsGeometryCollection *c = qgsgeometry_cast<const QgsGeometryCollection *>( unionGeom.constGet() );
+      if ( ( c && c->partCount() > 1 ) || !unionGeom.convertToSingleType() )
+      {
+        visibleMessageBar()->pushMessage(
+          tr( "Merge failed" ),
+          tr( "Resulting geometry type (multipart) is incompatible with layer type (singlepart)." ),
+          Qgis::MessageLevel::Critical );
+        return;
+      }
     }
-    newAttributes[ i ] = val;
-  }
-
-  vl->beginEditCommand( tr( "Merged features" ) );
-
-  QgsFeature mergeFeature;
-  if ( mergeFeatureId == FID_NULL )
-  {
-    // Create new feature
-    mergeFeature = QgsVectorLayerUtils::createFeature( vl, unionGeom, newAttributes );
-  }
-  else
-  {
-    // Merge into existing feature
-    featureIdsAfter.remove( mergeFeatureId );
-  }
-
-  // Delete other features
-  QgsFeatureIds::const_iterator feature_it = featureIdsAfter.constBegin();
-  for ( ; feature_it != featureIdsAfter.constEnd(); ++feature_it )
-  {
-    vl->deleteFeature( *feature_it );
   }
 
+  QString errorMessage;
+  QgsVectorLayerEditUtils vectorLayerEditUtils( vl );
+  bool success = vectorLayerEditUtils.mergeFeatures( d.targetFeatureId(), vl->selectedFeatureIds(), d.mergedAttributes(), unionGeom, errorMessage );
 
-  if ( mergeFeatureId == FID_NULL )
+  if ( !success )
   {
-    // Add the new feature
-    vl->addFeature( mergeFeature );
+    visibleMessageBar()->pushMessage(
+      tr( "Merge failed" ),
+      errorMessage,
+      Qgis::MessageLevel::Critical );
   }
-  else
+  else if ( success && !errorMessage.isEmpty() )
   {
-    // Modify merge feature
-    vl->changeGeometry( mergeFeatureId, unionGeom );
-    vl->changeAttributeValues( mergeFeatureId, newAttributes );
+    visibleMessageBar()->pushMessage(
+      tr( "Invalid result" ),
+      errorMessage,
+      Qgis::MessageLevel::Warning );
   }
-
-  vl->endEditCommand();
-
-  vl->triggerRepaint();
 }
 
 void QgisApp::vertexTool()

src/app/qgsmergeattributesdialog.cpp

@@ -108,6 +108,9 @@ QgsMergeAttributesDialog::QgsMergeAttributesDialog( const QgsFeatureList &featur
       break;
   }
 
+  if ( ! mFeatureList.isEmpty() )
+    mTargetFeatureId = mFeatureList.first().id();
+
   connect( mSkipAllButton, &QAbstractButton::clicked, this, &QgsMergeAttributesDialog::setAllToSkip );
   connect( mTableWidget, &QTableWidget::cellChanged, this, &QgsMergeAttributesDialog::tableWidgetCellChanged );
 
@@ -465,6 +468,8 @@ void QgsMergeAttributesDialog::setAllAttributesFromFeature( QgsFeatureId feature
       currentComboBox->setCurrentIndex( currentComboBox->findData( QStringLiteral( "f%1" ).arg( FID_TO_STRING( featureId ) ) ) );
     }
   }
+
+  mTargetFeatureId = featureId;
 }
 
 QVariant QgsMergeAttributesDialog::calcStatistic( int col, QgsStatisticalSummary::Statistic stat )
@@ -666,12 +671,18 @@ void QgsMergeAttributesDialog::mRemoveFeatureFromSelectionButton_clicked()
         f_it != mFeatureList.end();
         ++f_it )
   {
+    if ( f_it->id() == mTargetFeatureId )
+      mTargetFeatureId = FID_NULL;
+
     if ( f_it->id() == featureId )
     {
       mFeatureList.erase( f_it );
       break;
     }
   }
+
+  if ( mTargetFeatureId == FID_NULL && !mFeatureList.isEmpty() )
+    mTargetFeatureId = mFeatureList.first().id();
 }
 
 void QgsMergeAttributesDialog::tableWidgetCellChanged( int row, int column )
@@ -745,6 +756,11 @@ QgsAttributes QgsMergeAttributesDialog::mergedAttributes() const
   return results;
 }
 
+QgsFeatureId QgsMergeAttributesDialog::targetFeatureId() const
+{
+  return mTargetFeatureId;
+}
+
 QSet<int> QgsMergeAttributesDialog::skippedAttributeIndexes() const
 {
   QSet<int> skipped;

src/app/qgsmergeattributesdialog.h

@@ -49,6 +49,18 @@ class APP_EXPORT QgsMergeAttributesDialog: public QDialog, private Ui::QgsMergeA
 
     QgsAttributes mergedAttributes() const;
 
+    /**
+     * Returns the id of the target feature.
+     * By default it is the first feature of the list. Otherwise the feature explicitly selected
+     * with buttons "Take attributes from selected feature" or "Take attributes from feature with
+     * the largest area".
+     *
+     * \returns The id of the target feature.
+     *
+     * \since QGIS 3.30
+     */
+    QgsFeatureId targetFeatureId() const;
+
     /**
      * Returns a list of attribute indexes which should be skipped when merging (e.g., attributes
      * which have been set to "skip"
@@ -102,6 +114,7 @@ class APP_EXPORT QgsMergeAttributesDialog: public QDialog, private Ui::QgsMergeA
     void createRubberBandForFeature( QgsFeatureId featureId );
 
     QgsFeatureList mFeatureList;
+    QgsFeatureId mTargetFeatureId = FID_NULL;
     QgsVectorLayer *mVectorLayer = nullptr;
     QgsMapCanvas *mMapCanvas = nullptr;
     //! Item that highlights the selected feature in the merge table

src/core/vector/qgsvectorlayereditutils.cpp

@@ -721,6 +721,56 @@ int QgsVectorLayerEditUtils::addTopologicalPoints( const QgsPointXY &p )
   return addTopologicalPoints( QgsPoint( p ) );
 }
 
+bool QgsVectorLayerEditUtils::mergeFeatures( const QgsFeatureId &targetFeatureId, const QgsFeatureIds &mergeFeatureIds, const QgsAttributes &mergeAttributes, const QgsGeometry &unionGeometry, QString &errorMessage )
+{
+  errorMessage.clear();
+
+  if ( mergeFeatureIds.isEmpty() )
+  {
+    errorMessage = QObject::tr( "List of features to merge is empty" );
+    return false;
+  }
+
+  QgsAttributeMap newAttributes;
+  for ( int i = 0; i < mergeAttributes.count(); ++i )
+  {
+    QVariant val = mergeAttributes.at( i );
+
+    bool isDefaultValue = mLayer->fields().fieldOrigin( i ) == QgsFields::OriginProvider &&
+                          mLayer->dataProvider() &&
+                          mLayer->dataProvider()->defaultValueClause( mLayer->fields().fieldOriginIndex( i ) ) == val;
+
+    // convert to destination data type
+    QString errorMessageConvertCompatible;
+    if ( !isDefaultValue && !mLayer->fields().at( i ).convertCompatible( val, &errorMessageConvertCompatible ) )
+    {
+      if ( errorMessage.isEmpty() )
+        errorMessage = QObject::tr( "Could not store value '%1' in field of type %2: %3" ).arg( mergeAttributes.at( i ).toString(), mLayer->fields().at( i ).typeName(), errorMessageConvertCompatible );
+    }
+    newAttributes[ i ] = val;
+  }
+
+  mLayer->beginEditCommand( QObject::tr( "Merged features" ) );
+
+  // Delete other features but the target feature
+  QgsFeatureIds::const_iterator feature_it = mergeFeatureIds.constBegin();
+  for ( ; feature_it != mergeFeatureIds.constEnd(); ++feature_it )
+  {
+    if ( *feature_it != targetFeatureId )
+      mLayer->deleteFeature( *feature_it );
+  }
+
+  // Modify merge feature
+  QgsGeometry mergeGeometry = unionGeometry;
+  mLayer->changeGeometry( targetFeatureId, mergeGeometry );
+  mLayer->changeAttributeValues( targetFeatureId, newAttributes );
+
+  mLayer->endEditCommand();
+
+  mLayer->triggerRepaint();
+
+  return true;
+}
 
 bool QgsVectorLayerEditUtils::boundingBoxFromPointList( const QgsPointSequence &list, double &xmin, double &ymin, double &xmax, double &ymax ) const
 {

src/core/vector/qgsvectorlayereditutils.h

@@ -268,6 +268,20 @@ class CORE_EXPORT QgsVectorLayerEditUtils
      */
     int addTopologicalPoints( const QgsPointSequence &ps );
 
+    /**
+     * Merge features into a single one.
+     * \param targetFeatureId id of the target feature (will be updated)
+     * \param mergeFeatureIds id list of features to merge (will be deleted)
+     * \param mergeAttributes are the resulting attributes in the merged feature
+     * \param unionGeometry is the resulting geometry of the merged feature
+     * \param errorMessage will be set to a descriptive error message if any occurs
+     *
+     * \returns TRUE if the merge was successful, or FALSE if the operation failed.
+     *
+     * \since QGIS 3.30
+     */
+    bool mergeFeatures( const QgsFeatureId &targetFeatureId, const QgsFeatureIds &mergeFeatureIds, const QgsAttributes &mergeAttributes, const QgsGeometry &unionGeometry, QString &errorMessage SIP_OUT );
+
   private:
 
     /**

tests/src/app/CMakeLists.txt

@@ -46,6 +46,7 @@ set(TESTS
   testqgsmeshcalculatordialog.cpp
   testqgsgpsinformationwidget.cpp
   testqgslabelpropertydialog.cpp
+  testqgsmergeattributesdialog.cpp
 )
 
 if (HAVE_GEOREFERENCER)

tests/src/app/testqgsmergeattributesdialog.cpp

@@ -0,0 +1,97 @@
+/***************************************************************************
+     testqgsmergeattributesdialog.cpp
+     --------------------------------
+    Date                 : Feb 2023
+    Copyright            : (C) 2023 by Damiano Lombardi
+    Email                : damiano at opengis dot ch
+ ***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgstest.h"
+#include <QObject>
+
+#include "qgisapp.h"
+#include "qgsapplication.h"
+#include "qgsvectorlayer.h"
+#include "qgsmergeattributesdialog.h"
+
+class TestQgsMergeattributesDialog : public QObject
+{
+    Q_OBJECT
+
+  public:
+    TestQgsMergeattributesDialog() = default;
+
+  private:
+    QgisApp *mQgisApp = nullptr;
+
+  private slots:
+
+    void initTestCase()
+    {
+      QgsApplication::init();
+      QgsApplication::initQgis();
+      mQgisApp = new QgisApp();
+    }
+
+    void cleanupTestCase()
+    {
+      QgsApplication::exitQgis();
+    }
+
+    void test()
+    {
+      // Create test layer
+      QgsVectorFileWriter::SaveVectorOptions options;
+      QgsVectorLayer ml( "Polygon", "test", "memory" );
+      QVERIFY( ml.isValid() );
+      QTemporaryFile tmpFile( QDir::tempPath() +  "/TestQgsMergeattributesDialog" );
+      tmpFile.open();
+      const QString fileName( tmpFile.fileName( ) );
+      options.driverName = "GPKG";
+      options.layerName = "test";
+      QString newFilename;
+      const QgsVectorFileWriter::WriterError error( QgsVectorFileWriter::writeAsVectorFormatV3(
+            &ml,
+            fileName,
+            ml.transformContext(),
+            options, nullptr,
+            &newFilename ) );
+
+      QCOMPARE( error, QgsVectorFileWriter::WriterError::NoError );
+      QgsVectorLayer layer( QStringLiteral( "%1|layername=test" ).arg( newFilename ), "src_test", "ogr" );
+      QVERIFY( layer.startEditing() );
+      QgsVectorDataProvider *pr = layer.dataProvider();
+
+      // Create a feature
+      QgsFeature f1( layer.fields(), 1 );
+      f1.setGeometry( QgsGeometry::fromWkt( "POLYGON((0 0, 5 0, 5 5, 0 5, 0 0))" ) );
+      QVERIFY( pr->addFeature( f1 ) );
+      QCOMPARE( layer.featureCount(), 1 );
+
+      // And a bigger feature
+      QgsFeature f2( layer.fields(), 2 );
+      f2.setGeometry( QgsGeometry::fromWkt( "POLYGON((3 3, 10 3, 10 10, 3 10, 3 3))" ) );
+      QVERIFY( pr->addFeature( f2 ) );
+      QCOMPARE( layer.featureCount(), 2 );
+
+      // Merge the attributes together
+      QgsMergeAttributesDialog dialog( QgsFeatureList() << f1 << f2, &layer, mQgisApp->mapCanvas() );
+
+      // At beginnning the first feature of the list is the target
+      QCOMPARE( dialog.targetFeatureId(), f1.id() );
+
+      // Check after taking feature with largest geometry
+      QVERIFY( QMetaObject::invokeMethod( &dialog, "mFromLargestPushButton_clicked" ) );
+      QCOMPARE( dialog.targetFeatureId(), f2.id() );
+    }
+};
+
+QGSTEST_MAIN( TestQgsMergeattributesDialog )
+#include "testqgsmergeattributesdialog.moc"