[Geometry checker] Don't make line intersection test report symmetric…

… errors twice

src/analysis/vector/geometry_checker/qgsgeometrylineintersectioncheck.cpp

@@ -19,10 +19,14 @@
 void QgsGeometryLineIntersectionCheck::collectErrors( QList<QgsGeometryCheckError *> &errors, QStringList &/*messages*/, QAtomicInt *progressCounter, const QMap<QString, QgsFeatureIds> &ids ) const
 {
   QMap<QString, QgsFeatureIds> featureIds = ids.isEmpty() ? allLayerFeatureIds() : ids;
-  QgsGeometryCheckerUtils::LayerFeatures layerFeatures( mContext->featurePools, featureIds, mCompatibleGeometryTypes, progressCounter, true );
-  for ( const QgsGeometryCheckerUtils::LayerFeature &layerFeature : layerFeatures )
+  QgsGeometryCheckerUtils::LayerFeatures layerFeaturesA( mContext->featurePools, featureIds, mCompatibleGeometryTypes, progressCounter, true );
+  QList<QString> layerIds = featureIds.keys();
+  for ( const QgsGeometryCheckerUtils::LayerFeature &layerFeatureA : layerFeaturesA )
   {
-    const QgsAbstractGeometry *geom = layerFeature.geometry();
+    // Ensure each pair of layers only gets compared once: remove the current layer from the layerIds, but add it to the layerList for layerFeaturesB
+    layerIds.removeOne( layerFeatureA.layer().id() );
+
+    const QgsAbstractGeometry *geom = layerFeatureA.geometry();
     for ( int iPart = 0, nParts = geom->partCount(); iPart < nParts; ++iPart )
     {
       const QgsLineString *line = dynamic_cast<const QgsLineString *>( QgsGeometryCheckerUtils::getGeomPart( geom, iPart ) );
@@ -33,17 +37,23 @@ void QgsGeometryLineIntersectionCheck::collectErrors( QList<QgsGeometryCheckErro
       }
 
       // Check whether the line intersects with any other lines
-      QgsGeometryCheckerUtils::LayerFeatures checkFeatures( mContext->featurePools, featureIds.keys(), line->boundingBox(), {QgsWkbTypes::LineGeometry} );
-      for ( const QgsGeometryCheckerUtils::LayerFeature &checkFeature : checkFeatures )
+      QgsGeometryCheckerUtils::LayerFeatures layerFeaturesB( mContext->featurePools, QList<QString>() << layerFeatureA.layer().id() << layerIds, line->boundingBox(), {QgsWkbTypes::LineGeometry} );
+      for ( const QgsGeometryCheckerUtils::LayerFeature &layerFeatureB : layerFeaturesB )
       {
-        if ( checkFeature == layerFeature )
+        // > : only report intersections within same layer once
+        if ( layerFeatureA.layer().id() == layerFeatureB.layer().id() && layerFeatureB.feature().id() > layerFeatureA.feature().id() )
         {
-          // Skip current feature
           continue;
         }
-        const QgsAbstractGeometry *testGeom = checkFeature.geometry();
+
+        const QgsAbstractGeometry *testGeom = layerFeatureB.geometry();
         for ( int jPart = 0, mParts = testGeom->partCount(); jPart < mParts; ++jPart )
         {
+          // Skip current feature part, only report intersections within same part once
+          if ( layerFeatureB.feature().id() == layerFeatureA.feature().id() && iPart >= jPart )
+          {
+            continue;
+          }
           const QgsLineString *testLine = dynamic_cast<const QgsLineString *>( QgsGeometryCheckerUtils::getGeomPart( testGeom, jPart ) );
           if ( !testLine )
           {