Add a pure virtual clone method to processing parameter definitions

And use it when we need to clone parameters (instead of more fragile
conversion to and from variants)

This fixes model loading which use algorithms which create python
subclasses of parameter definitions

python/core/processing/qgsprocessingparameters.sip

@@ -213,6 +213,12 @@ class QgsProcessingParameterDefinition
 
     virtual ~QgsProcessingParameterDefinition();
 
+    virtual QgsProcessingParameterDefinition *clone() const = 0 /Factory/;
+%Docstring
+ Creates a clone of the parameter definition.
+ :rtype: QgsProcessingParameterDefinition
+%End
+
     virtual QString type() const = 0;
 %Docstring
  Unique parameter type name.
@@ -620,6 +626,8 @@ class QgsProcessingParameterBoolean : QgsProcessingParameterDefinition
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual QString valueAsPythonString( const QVariant &value, QgsProcessingContext &context ) const;
 
@@ -656,6 +664,8 @@ class QgsProcessingParameterCrs : QgsProcessingParameterDefinition
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = 0 ) const;
 
@@ -693,6 +703,8 @@ class QgsProcessingParameterMapLayer : QgsProcessingParameterDefinition
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = 0 ) const;
 
@@ -730,6 +742,8 @@ class QgsProcessingParameterExtent : QgsProcessingParameterDefinition
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = 0 ) const;
 
@@ -768,6 +782,8 @@ class QgsProcessingParameterPoint : QgsProcessingParameterDefinition
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = 0 ) const;
 
@@ -809,6 +825,8 @@ class QgsProcessingParameterFile : QgsProcessingParameterDefinition
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = 0 ) const;
 
@@ -879,6 +897,8 @@ class QgsProcessingParameterMatrix : QgsProcessingParameterDefinition
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = 0 ) const;
 
@@ -967,6 +987,8 @@ class QgsProcessingParameterMultipleLayers : QgsProcessingParameterDefinition
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = 0 ) const;
 
@@ -1050,6 +1072,8 @@ class QgsProcessingParameterNumber : QgsProcessingParameterDefinition
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = 0 ) const;
 
@@ -1133,6 +1157,8 @@ class QgsProcessingParameterRange : QgsProcessingParameterDefinition
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = 0 ) const;
 
@@ -1188,6 +1214,8 @@ class QgsProcessingParameterRasterLayer : QgsProcessingParameterDefinition
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = 0 ) const;
 
@@ -1227,6 +1255,8 @@ class QgsProcessingParameterEnum : QgsProcessingParameterDefinition
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = 0 ) const;
 
@@ -1298,6 +1328,8 @@ class QgsProcessingParameterString : QgsProcessingParameterDefinition
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual QString valueAsPythonString( const QVariant &value, QgsProcessingContext &context ) const;
 
@@ -1354,6 +1386,8 @@ class QgsProcessingParameterExpression : QgsProcessingParameterDefinition
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual QString valueAsPythonString( const QVariant &value, QgsProcessingContext &context ) const;
 
@@ -1413,6 +1447,8 @@ class QgsProcessingParameterVectorLayer : QgsProcessingParameterDefinition
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = 0 ) const;
 
@@ -1479,6 +1515,8 @@ class QgsProcessingParameterField : QgsProcessingParameterDefinition
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = 0 ) const;
 
@@ -1565,6 +1603,8 @@ class QgsProcessingParameterFeatureSource : QgsProcessingParameterDefinition
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = 0 ) const;
 
@@ -1704,6 +1744,8 @@ class QgsProcessingParameterFeatureSink : QgsProcessingDestinationParameter
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = 0 ) const;
 
@@ -1781,6 +1823,8 @@ class QgsProcessingParameterVectorDestination : QgsProcessingDestinationParamete
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = 0 ) const;
 
@@ -1852,6 +1896,8 @@ class QgsProcessingParameterRasterDestination : QgsProcessingDestinationParamete
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = 0 ) const;
 
@@ -1895,6 +1941,8 @@ class QgsProcessingParameterFileDestination : QgsProcessingDestinationParameter
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = 0 ) const;
 
@@ -1958,6 +2006,8 @@ class QgsProcessingParameterFolderDestination : QgsProcessingDestinationParamete
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = 0 ) const;
 
@@ -1998,6 +2048,8 @@ class QgsProcessingParameterBand : QgsProcessingParameterDefinition
  Returns the type name for the parameter class.
  :rtype: str
 %End
+    virtual QgsProcessingParameterDefinition *clone() const /Factory/;
+
     virtual QString type() const;
     virtual bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = 0 ) const;
 

python/plugins/processing/algs/gdal/buildvrt.py

@@ -63,6 +63,10 @@ class ParameterVrtDestination(QgsProcessingParameterRasterDestination):
             def __init__(self, name, description):
                 super().__init__(name, description)
 
+            def clone(self):
+                copy = ParameterVrtDestination(self.name(), self.description())
+                return copy
+
             def type(self):
                 return 'vrt_destination'
 

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

@@ -78,6 +78,10 @@ def __init__(self, name, description, parentLayerParameterName='INPUT'):
                 super().__init__(name, description)
                 self._parentLayerParameter = parentLayerParameterName
 
+            def clone(self):
+                copy = ParameterAggregates(self.name(), self.description(), self._parentLayerParameter)
+                return copy
+
             def type(self):
                 return 'aggregates'
 

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

@@ -26,18 +26,12 @@
 __revision__ = '$Format:%H$'
 
 from qgis.core import (
-    QgsApplication,
     QgsDistanceArea,
     QgsExpression,
-    QgsFeature,
-    QgsFeatureSink,
     QgsField,
     QgsFields,
     QgsProcessingException,
-    QgsProcessingParameterDefinition,
-    QgsProcessingUtils,
-    QgsProject,
-)
+    QgsProcessingParameterDefinition)
 
 from processing.algs.qgis.QgisAlgorithm import QgisFeatureBasedAlgorithm
 
@@ -59,6 +53,10 @@ def __init__(self, name, description, parentLayerParameterName='INPUT'):
                 super().__init__(name, description)
                 self._parentLayerParameter = parentLayerParameterName
 
+            def clone(self):
+                copy = ParameterFieldsMapping(self.name(), self.description(), self._parentLayerParameter)
+                return copy
+
             def type(self):
                 return 'fields_mapping'
 

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

@@ -116,6 +116,10 @@ def __init__(self, name='', description='', parent_layer=None, radius_param=None
                 self.radius_param = radius_param
                 self.radius_field_param = radius_field_param
 
+            def clone(self):
+                copy = ParameterHeatmapPixelSize(self.name(), self.description(), self.parent_layer, self.radius_param, self.radius_field_param, self.minimum(), self.maximum(), self.defaultValue((), self.flags() & QgsProcessingParameterDefinition.FlagOptional))
+                return copy
+
         pixel_size_param = ParameterHeatmapPixelSize(self.PIXEL_SIZE,
                                                      self.tr('Output raster size'),
                                                      parent_layer=self.INPUT,

src/core/processing/models/qgsprocessingmodelalgorithm.cpp

@@ -729,19 +729,19 @@ void QgsProcessingModelAlgorithm::updateDestinationParameters()
       if ( !source )
         continue;
 
-      QgsProcessingParameterDefinition *param = QgsProcessingParameters::parameterFromVariantMap( source->toVariantMap() );
+      std::unique_ptr< QgsProcessingParameterDefinition > param( source->clone() );
       param->setName( outputIt->childId() + ':' + outputIt->name() );
       param->setDescription( outputIt->description() );
-      addParameter( param );
 
-      if ( const QgsProcessingDestinationParameter *destParam = dynamic_cast< const QgsProcessingDestinationParameter *>( param ) )
+      if ( const QgsProcessingDestinationParameter *destParam = dynamic_cast< const QgsProcessingDestinationParameter *>( param.get() ) )
       {
-        QgsProcessingOutputDefinition *output = destParam->toOutputDefinition();
+        std::unique_ptr< QgsProcessingOutputDefinition > output( destParam->toOutputDefinition() );
         if ( output )
         {
-          addOutput( output );
+          addOutput( output.release() );
         }
       }
+      addParameter( param.release() );
     }
   }
 }
@@ -793,8 +793,11 @@ bool QgsProcessingModelAlgorithm::loadVariant( const QVariant &model )
   for ( ; childIt != childMap.constEnd(); ++childIt )
   {
     QgsProcessingModelChildAlgorithm child;
+    // we be leniant here - even if we couldn't load a parameter, don't interrupt the model loading
+    // otherwise models may become unusable (e.g. due to removed plugins providing algs/parameters)
+    // with no way for users to repair them
     if ( !child.loadVariant( childIt.value() ) )
-      return false;
+      continue;
 
     mChildAlgorithms.insert( child.childId(), child );
   }
@@ -817,11 +820,12 @@ bool QgsProcessingModelAlgorithm::loadVariant( const QVariant &model )
   QVariantMap::const_iterator paramDefIt = paramDefMap.constBegin();
   for ( ; paramDefIt != paramDefMap.constEnd(); ++paramDefIt )
   {
-    QgsProcessingParameterDefinition *param = QgsProcessingParameters::parameterFromVariantMap( paramDefIt.value().toMap() );
-    if ( !param )
-      return false;
-
-    addParameter( param );
+    std::unique_ptr< QgsProcessingParameterDefinition > param( QgsProcessingParameters::parameterFromVariantMap( paramDefIt.value().toMap() ) );
+    // we be leniant here - even if we couldn't load a parameter, don't interrupt the model loading
+    // otherwise models may become unusable (e.g. due to removed plugins providing algs/parameters)
+    // with no way for users to repair them
+    if ( param )
+      addParameter( param.release() );
   }
 
   updateDestinationParameters();