QgsDistanceArea methods should raise QgsCsException when errors occur

Instead of just silently return "0", which is misleading and can result in data corruption/incorrect analysis results. Better to be safe and force callers to handle transformation errors appropriately. In this case we: - raise QgsProcessingExceptions when the failed measurement is coming from a processing tool, so that the user is forced to deal with the issue and we aren't providing meaningless/misleading measurements - report evaluation errors if the measurement is coming from a QGIS expression, so the user must appropriately handle the situation - for all other cases we currently just write a console error and maintain the current behavior of treating the measurement length as 0. TODO notes have been added to handle this cases better.
qgis · Sep 21, 2024 · cde770e · cde770e
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diff --git a/python/PyQt6/core/auto_generated/qgsdistancearea.sip.in b/python/PyQt6/core/auto_generated/qgsdistancearea.sip.in
@@ -148,7 +148,7 @@ The inverse flattening is calculated with invf = a/(a-b).
 .. seealso:: :py:func:`ellipsoidSemiMinor`
 %End
 
-    double measureArea( const QgsGeometry &geometry ) const;
+    double measureArea( const QgsGeometry &geometry ) const throw( QgsCsException );
 %Docstring
 Measures the area of a geometry.
 
@@ -162,9 +162,11 @@ Measures the area of a geometry.
 .. seealso:: :py:func:`measurePerimeter`
 
 .. seealso:: :py:func:`areaUnits`
+
+:raises QgsCsException: if a transformation error occurs while calculating the area
 %End
 
-    double measureLength( const QgsGeometry &geometry ) const;
+    double measureLength( const QgsGeometry &geometry ) const throw( QgsCsException );
 %Docstring
 Measures the length of a geometry.
 
@@ -178,9 +180,11 @@ Measures the length of a geometry.
 .. seealso:: :py:func:`measureArea`
 
 .. seealso:: :py:func:`measurePerimeter`
+
+:raises QgsCsException: if a transformation error occurs while calculating the length
 %End
 
-    double measurePerimeter( const QgsGeometry &geometry ) const;
+    double measurePerimeter( const QgsGeometry &geometry ) const throw( QgsCsException );
 %Docstring
 Measures the perimeter of a polygon geometry.
 
@@ -194,20 +198,24 @@ Measures the perimeter of a polygon geometry.
 .. seealso:: :py:func:`measureArea`
 
 .. seealso:: :py:func:`measurePerimeter`
+
+:raises QgsCsException: if a transformation error occurs while calculating the perimeter
 %End
 
-    double measureLine( const QVector<QgsPointXY> &points ) const;
+    double measureLine( const QVector<QgsPointXY> &points ) const throw( QgsCsException );
 %Docstring
 Measures the length of a line with multiple segments.
 
 :param points: list of points in line
 
 :return: length of line. The units for the returned length can be retrieved by calling :py:func:`~QgsDistanceArea.lengthUnits`.
 
+:raises QgsCsException: if a transformation error occurs while calculating the length
+
 .. seealso:: :py:func:`lengthUnits`
 %End
 
-    double measureLine( const QgsPointXY &p1, const QgsPointXY &p2 ) const;
+    double measureLine( const QgsPointXY &p1, const QgsPointXY &p2 ) const throw( QgsCsException );
 %Docstring
 Measures the distance between two points.
 
@@ -216,6 +224,8 @@ Measures the distance between two points.
 
 :return: distance between points. The units for the returned distance can be retrieved by calling :py:func:`~QgsDistanceArea.lengthUnits`.
 
+:raises QgsCsException: if a transformation error occurs while calculating the length
+
 .. seealso:: :py:func:`lengthUnits`
 %End
 
@@ -255,9 +265,11 @@ Returns the units of area for areal calculations made by this object.
 .. seealso:: :py:func:`lengthUnits`
 %End
 
-    double measurePolygon( const QVector<QgsPointXY> &points ) const;
+    double measurePolygon( const QVector<QgsPointXY> &points ) const throw( QgsCsException );
 %Docstring
 Measures the area of the polygon described by a set of points.
+
+:raises QgsCsException: if a transformation error occurs while calculating the area.
 %End
 
     double bearing( const QgsPointXY &p1, const QgsPointXY &p2 ) const throw( QgsCsException );

diff --git a/python/core/auto_generated/qgsdistancearea.sip.in b/python/core/auto_generated/qgsdistancearea.sip.in
@@ -148,7 +148,7 @@ The inverse flattening is calculated with invf = a/(a-b).
 .. seealso:: :py:func:`ellipsoidSemiMinor`
 %End
 
-    double measureArea( const QgsGeometry &geometry ) const;
+    double measureArea( const QgsGeometry &geometry ) const throw( QgsCsException );
 %Docstring
 Measures the area of a geometry.
 
@@ -162,9 +162,11 @@ Measures the area of a geometry.
 .. seealso:: :py:func:`measurePerimeter`
 
 .. seealso:: :py:func:`areaUnits`
+
+:raises QgsCsException: if a transformation error occurs while calculating the area
 %End
 
-    double measureLength( const QgsGeometry &geometry ) const;
+    double measureLength( const QgsGeometry &geometry ) const throw( QgsCsException );
 %Docstring
 Measures the length of a geometry.
 
@@ -178,9 +180,11 @@ Measures the length of a geometry.
 .. seealso:: :py:func:`measureArea`
 
 .. seealso:: :py:func:`measurePerimeter`
+
+:raises QgsCsException: if a transformation error occurs while calculating the length
 %End
 
-    double measurePerimeter( const QgsGeometry &geometry ) const;
+    double measurePerimeter( const QgsGeometry &geometry ) const throw( QgsCsException );
 %Docstring
 Measures the perimeter of a polygon geometry.
 
@@ -194,20 +198,24 @@ Measures the perimeter of a polygon geometry.
 .. seealso:: :py:func:`measureArea`
 
 .. seealso:: :py:func:`measurePerimeter`
+
+:raises QgsCsException: if a transformation error occurs while calculating the perimeter
 %End
 
-    double measureLine( const QVector<QgsPointXY> &points ) const;
+    double measureLine( const QVector<QgsPointXY> &points ) const throw( QgsCsException );
 %Docstring
 Measures the length of a line with multiple segments.
 
 :param points: list of points in line
 
 :return: length of line. The units for the returned length can be retrieved by calling :py:func:`~QgsDistanceArea.lengthUnits`.
 
+:raises QgsCsException: if a transformation error occurs while calculating the length
+
 .. seealso:: :py:func:`lengthUnits`
 %End
 
-    double measureLine( const QgsPointXY &p1, const QgsPointXY &p2 ) const;
+    double measureLine( const QgsPointXY &p1, const QgsPointXY &p2 ) const throw( QgsCsException );
 %Docstring
 Measures the distance between two points.
 
@@ -216,6 +224,8 @@ Measures the distance between two points.
 
 :return: distance between points. The units for the returned distance can be retrieved by calling :py:func:`~QgsDistanceArea.lengthUnits`.
 
+:raises QgsCsException: if a transformation error occurs while calculating the length
+
 .. seealso:: :py:func:`lengthUnits`
 %End
 
@@ -255,9 +265,11 @@ Returns the units of area for areal calculations made by this object.
 .. seealso:: :py:func:`lengthUnits`
 %End
 
-    double measurePolygon( const QVector<QgsPointXY> &points ) const;
+    double measurePolygon( const QVector<QgsPointXY> &points ) const throw( QgsCsException );
 %Docstring
 Measures the area of the polygon described by a set of points.
+
+:raises QgsCsException: if a transformation error occurs while calculating the area.
 %End
 
     double bearing( const QgsPointXY &p1, const QgsPointXY &p2 ) const throw( QgsCsException );

diff --git a/src/analysis/network/qgsvectorlayerdirector.cpp b/src/analysis/network/qgsvectorlayerdirector.cpp
@@ -27,7 +27,7 @@
 #include "qgsgeometry.h"
 #include "qgsdistancearea.h"
 #include "qgswkbtypes.h"
-
+#include "qgslogger.h"
 #include <QString>
 #include <QtAlgorithms>
 
@@ -381,7 +381,17 @@ void QgsVectorLayerDirector::makeGraph( QgsGraphBuilderInterface *builder, const
 
             if ( !isFirstPoint && arcPt1 != arcPt2 )
             {
-              double distance = builder->distanceArea()->measureLine( arcPt1, arcPt2 );
+              double distance = 0;
+              try
+              {
+                distance = builder->distanceArea()->measureLine( arcPt1, arcPt2 );
+              }
+              catch ( QgsCsException & )
+              {
+                // TODO report errors to user
+                QgsDebugError( QStringLiteral( "An error occurred while calculating length" ) );
+              }
+
               QVector< QVariant > prop;
               prop.reserve( mStrategies.size() );
               for ( QgsNetworkStrategy *strategy : mStrategies )

diff --git a/src/analysis/processing/qgsalgorithmcalculateoverlaps.cpp b/src/analysis/processing/qgsalgorithmcalculateoverlaps.cpp
@@ -155,7 +155,16 @@ QVariantMap QgsCalculateVectorOverlapsAlgorithm::processAlgorithm( const QVarian
     if ( feature.hasGeometry() && !qgsDoubleNear( feature.geometry().area(), 0.0 ) )
     {
       const QgsGeometry inputGeom = feature.geometry();
-      const double inputArea = da.measureArea( inputGeom );
+
+      double inputArea = 0;
+      try
+      {
+        inputArea = da.measureArea( inputGeom );
+      }
+      catch ( QgsCsException & )
+      {
+        throw QgsProcessingException( QObject::tr( "An error occurred while calculating feature area" ) );
+      }
 
       // prepare for lots of intersection tests (for speed)
       std::unique_ptr< QgsGeometryEngine > bufferGeomEngine( QgsGeometry::createGeometryEngine( inputGeom.constGet() ) );
@@ -195,7 +204,16 @@ QVariantMap QgsCalculateVectorOverlapsAlgorithm::processAlgorithm( const QVarian
 
         const QgsGeometry overlayIntersection = inputGeom.intersection( overlayDissolved, geometryParameters );
 
-        const double overlayArea = da.measureArea( overlayIntersection );
+        double overlayArea = 0;
+        try
+        {
+          overlayArea = da.measureArea( overlayIntersection );
+        }
+        catch ( QgsCsException & )
+        {
+          throw QgsProcessingException( QObject::tr( "An error occurred while calculating feature area" ) );
+        }
+
         outAttributes.append( overlayArea );
         outAttributes.append( 100 * overlayArea / inputArea );
       }

diff --git a/src/analysis/processing/qgsalgorithmlinedensity.cpp b/src/analysis/processing/qgsalgorithmlinedensity.cpp
@@ -190,7 +190,16 @@ QVariantMap QgsLineDensityAlgorithm::processAlgorithm( const QVariantMap &parame
 
           if ( engine->intersects( lineGeom.constGet() ) )
           {
-            const double analysisLineLength =  mDa.measureLength( QgsGeometry( engine->intersection( mIndex.geometry( id ).constGet() ) ) );
+            double analysisLineLength = 0;
+            try
+            {
+              analysisLineLength =  mDa.measureLength( QgsGeometry( engine->intersection( mIndex.geometry( id ).constGet() ) ) );
+            }
+            catch ( QgsCsException & )
+            {
+              throw QgsProcessingException( QObject::tr( "An error occurred while calculating feature length" ) );
+            }
+
             double weight = 1;
 
             if ( !mWeightField.isEmpty() )
@@ -206,7 +215,16 @@ QVariantMap QgsLineDensityAlgorithm::processAlgorithm( const QVariantMap &parame
         if ( absDensity > 0 )
         {
           //only calculate ellipsoidal area if abs density is greater 0
-          const double analysisSearchGeometryArea = mDa.measureArea( mSearchGeometry );
+          double analysisSearchGeometryArea = 0;
+          try
+          {
+            analysisSearchGeometryArea = mDa.measureArea( mSearchGeometry );
+          }
+          catch ( QgsCsException & )
+          {
+            throw QgsProcessingException( QObject::tr( "An error occurred while calculating feature area" ) );
+          }
+
           lineDensity = absDensity / analysisSearchGeometryArea;
         }
         rasterDataLine->setValue( 0, col, lineDensity );

diff --git a/src/analysis/processing/qgsalgorithmnearestneighbouranalysis.cpp b/src/analysis/processing/qgsalgorithmnearestneighbouranalysis.cpp
@@ -113,7 +113,14 @@ QVariantMap QgsNearestNeighbourAnalysisAlgorithm::processAlgorithm( const QVaria
     }
 
     const QgsFeatureId neighbourId = spatialIndex.nearestNeighbor( f.geometry().asPoint(), 2 ).at( 1 );
-    sumDist += da.measureLine( spatialIndex.geometry( neighbourId ).asPoint(), f.geometry().asPoint() );
+    try
+    {
+      sumDist += da.measureLine( spatialIndex.geometry( neighbourId ).asPoint(), f.geometry().asPoint() );
+    }
+    catch ( QgsCsException & )
+    {
+      throw QgsProcessingException( QObject::tr( "An error occurred while calculating length" ) );
+    }
 
     i++;
     feedback->setProgress( i * step );

diff --git a/src/analysis/processing/qgsalgorithmpointstopaths.cpp b/src/analysis/processing/qgsalgorithmpointstopaths.cpp
@@ -353,7 +353,15 @@ QVariantMap QgsPointsToPathsAlgorithm::processAlgorithm( const QVariantMap &para
       for ( int i = 1; i < pathPoints.size(); ++i )
       {
         const double angle = pathPoints.at( i - 1 ).azimuth( pathPoints.at( i ) );
-        const double distance = da.measureLine( pathPoints.at( i - 1 ), pathPoints.at( i ) );
+        double distance = 0;
+        try
+        {
+          distance = da.measureLine( pathPoints.at( i - 1 ), pathPoints.at( i ) );
+        }
+        catch ( QgsCsException & )
+        {
+          throw QgsProcessingException( QObject::tr( "An error occurred while calculating length" ) );
+        }
         out << QString( "%1;%2;90\n" ).arg( angle ).arg( distance );
       }
     }

diff --git a/src/analysis/processing/qgsalgorithmserviceareafromlayer.cpp b/src/analysis/processing/qgsalgorithmserviceareafromlayer.cpp
@@ -165,7 +165,16 @@ QVariantMap QgsServiceAreaFromLayerAlgorithm::processAlgorithm( const QVariantMa
 
     if ( pointDistanceThreshold >= 0 )
     {
-      const double distancePointToNetwork = mBuilder->distanceArea()->measureLine( originalPoint, snappedPoint );
+      double distancePointToNetwork = 0;
+      try
+      {
+        distancePointToNetwork = mBuilder->distanceArea()->measureLine( originalPoint, snappedPoint );
+      }
+      catch ( QgsCsException & )
+      {
+        throw QgsProcessingException( QObject::tr( "An error occurred while calculating length" ) );
+      }
+
       if ( distancePointToNetwork > pointDistanceThreshold )
       {
         feedback->pushWarning( QObject::tr( "Point is too far from the network layer (%1, maximum permitted is %2)" ).arg( distancePointToNetwork ).arg( pointDistanceThreshold ) );

diff --git a/src/analysis/processing/qgsalgorithmserviceareafrompoint.cpp b/src/analysis/processing/qgsalgorithmserviceareafrompoint.cpp
@@ -113,7 +113,17 @@ QVariantMap QgsServiceAreaFromPointAlgorithm::processAlgorithm( const QVariantMa
   {
     const double pointDistanceThreshold = parameterAsDouble( parameters, QStringLiteral( "POINT_TOLERANCE" ), context );
 
-    const double distancePointToNetwork = mBuilder->distanceArea()->measureLine( startPoint, snappedStartPoint );
+    double distancePointToNetwork = 0;
+    try
+    {
+      distancePointToNetwork = mBuilder->distanceArea()->measureLine( startPoint, snappedStartPoint );
+    }
+    catch ( QgsCsException & )
+    {
+      throw QgsProcessingException( QObject::tr( "An error occurred while calculating length" ) );
+    }
+
+
     if ( distancePointToNetwork > pointDistanceThreshold )
     {
       throw QgsProcessingException( QObject::tr( "Point is too far from the network layer (%1, maximum permitted is %2)" ).arg( distancePointToNetwork ).arg( pointDistanceThreshold ) );

diff --git a/src/analysis/processing/qgsalgorithmshortestline.cpp b/src/analysis/processing/qgsalgorithmshortestline.cpp
@@ -155,7 +155,16 @@ QVariantMap QgsShortestLineAlgorithm::processAlgorithm( const QVariantMap &param
       }
 
       const QgsGeometry shortestLine = sourceGeom.shortestLine( destinationGeom );
-      double dist = da.measureLength( shortestLine );
+      double dist = 0;
+      try
+      {
+        dist = da.measureLength( shortestLine );
+      }
+      catch ( QgsCsException & )
+      {
+        throw QgsProcessingException( QObject::tr( "An error occurred while calculating shortest line length" ) );
+      }
+
       QgsFeature f;
       QgsAttributes attrs = sourceFeature.attributes();
       attrs << destinationAttributeCache.value( id ) << dist;

diff --git a/src/analysis/processing/qgsalgorithmshortestpathlayertopoint.cpp b/src/analysis/processing/qgsalgorithmshortestpathlayertopoint.cpp
@@ -107,7 +107,16 @@ QVariantMap QgsShortestPathLayerToPointAlgorithm::processAlgorithm( const QVaria
 
   if ( pointDistanceThreshold >= 0 )
   {
-    const double distanceEndPointToNetwork = mBuilder->distanceArea()->measureLine( endPoint, snappedEndPoint );
+    double distanceEndPointToNetwork = 0;
+    try
+    {
+      distanceEndPointToNetwork = mBuilder->distanceArea()->measureLine( endPoint, snappedEndPoint );
+    }
+    catch ( QgsCsException & )
+    {
+      throw QgsProcessingException( QObject::tr( "An error occurred while calculating length" ) );
+    }
+
     if ( distanceEndPointToNetwork > pointDistanceThreshold )
     {
       throw QgsProcessingException( QObject::tr( "End point is too far from the network layer (%1, maximum permitted is %2)" ).arg( distanceEndPointToNetwork ).arg( pointDistanceThreshold ) );
@@ -143,7 +152,16 @@ QVariantMap QgsShortestPathLayerToPointAlgorithm::processAlgorithm( const QVaria
 
     if ( pointDistanceThreshold >= 0 )
     {
-      const double distancePointToNetwork = mBuilder->distanceArea()->measureLine( originalPoint, snappedPoint );
+      double distancePointToNetwork = 0;
+      try
+      {
+        distancePointToNetwork = mBuilder->distanceArea()->measureLine( originalPoint, snappedPoint );
+      }
+      catch ( QgsCsException & )
+      {
+        throw QgsProcessingException( QObject::tr( "An error occurred while calculating length" ) );
+      }
+
       if ( distancePointToNetwork > pointDistanceThreshold )
       {
         feedback->pushWarning( QObject::tr( "Point is too far from the network layer (%1, maximum permitted is %2)" ).arg( distancePointToNetwork ).arg( pointDistanceThreshold ) );