[processing] Ensure algorithms which add attributes to features

always add a consistent amount of attributes regardless of the
code paths taken

Some algorithms were adding features to data providers with
different number of attributes vs the layer's fields - this is
not supported and depending on the data provider will have
different (bad) results.

python/plugins/processing/algs/qgis/ExportGeometryInfo.py

@@ -30,7 +30,8 @@
 from qgis.PyQt.QtGui import QIcon
 from qgis.PyQt.QtCore import QVariant
 
-from qgis.core import (QgsCoordinateTransform,
+from qgis.core import (NULL,
+                       QgsCoordinateTransform,
                        QgsField,
                        QgsFields,
                        QgsWkbTypes,
@@ -148,6 +149,12 @@ def processAlgorithm(self, parameters, context, feedback):
                 else:
                     attrs.extend(self.line_attributes(inGeom))
 
+            # ensure consistent count of attributes - otherwise null
+            # geometry features will have incorrect attribute length
+            # and provider may reject them
+            if len(attrs) < len(fields):
+                attrs += [NULL] * (len(fields) - len(attrs))
+
             outFeat.setAttributes(attrs)
             sink.addFeature(outFeat, QgsFeatureSink.FastInsert)
 

python/plugins/processing/algs/qgis/SpatialJoinSummary.py

@@ -270,6 +270,13 @@ def addField(original, stat, type):
 
             if not f.hasGeometry():
                 if not discard_nomatch:
+                    # ensure consistent count of attributes - otherwise non matching
+                    # features will have incorrect attribute length
+                    # and provider may reject them
+                    attrs = f.attributes()
+                    if len(attrs) < len(out_fields):
+                        attrs += [NULL] * (len(out_fields) - len(attrs))
+                    f.setAttributes(attrs)
                     sink.addFeature(f, QgsFeatureSink.FastInsert)
                 continue
 
@@ -302,6 +309,13 @@ def addField(original, stat, type):
                 if discard_nomatch:
                     continue
                 else:
+                    # ensure consistent count of attributes - otherwise non matching
+                    # features will have incorrect attribute length
+                    # and provider may reject them
+                    attrs = f.attributes()
+                    if len(attrs) < len(out_fields):
+                        attrs += [NULL] * (len(out_fields) - len(attrs))
+                    f.setAttributes(attrs)
                     sink.addFeature(f, QgsFeatureSink.FastInsert)
             else:
                 attrs = f.attributes()

src/analysis/processing/qgsalgorithmboundingbox.cpp

@@ -86,6 +86,15 @@ QgsFeature QgsBoundingBoxAlgorithm::processFeature( const QgsFeature &feature, Q
           << bounds.perimeter();
     f.setAttributes( attrs );
   }
+  else
+  {
+    QgsAttributes attrs = f.attributes();
+    attrs << QVariant()
+          << QVariant()
+          << QVariant()
+          << QVariant();
+    f.setAttributes( attrs );
+  }
   return f;
 }
 

src/analysis/processing/qgsalgorithmconvexhull.cpp

@@ -85,6 +85,13 @@ QgsFeature QgsConvexHullAlgorithm::processFeature( const QgsFeature &feature, Qg
             << outputGeometry.constGet()->perimeter();
       f.setAttributes( attrs );
     }
+    else
+    {
+      QgsAttributes attrs = f.attributes();
+      attrs << QVariant()
+            << QVariant();
+      f.setAttributes( attrs );
+    }
   }
   return f;
 }

src/analysis/processing/qgsalgorithmminimumenclosingcircle.cpp

@@ -100,6 +100,13 @@ QgsFeature QgsMinimumEnclosingCircleAlgorithm::processFeature( const QgsFeature
           << M_PI *radius *radius;
     f.setAttributes( attrs );
   }
+  else
+  {
+    QgsAttributes attrs = f.attributes();
+    attrs << QVariant()
+          << QVariant();
+    f.setAttributes( attrs );
+  }
   return f;
 }
 

src/analysis/processing/qgsalgorithmorientedminimumboundingbox.cpp

@@ -96,6 +96,16 @@ QgsFeature QgsOrientedMinimumBoundingBoxAlgorithm::processFeature( const QgsFeat
           << 2 * width + 2 * height;
     f.setAttributes( attrs );
   }
+  else
+  {
+    QgsAttributes attrs = f.attributes();
+    attrs << QVariant()
+          << QVariant()
+          << QVariant()
+          << QVariant()
+          << QVariant();
+    f.setAttributes( attrs );
+  }
   return f;
 }