Add a pure virtual clone method for algorithms

This is required for safely executing the algorithm in a background
thread.

python/core/processing/qgsprocessingalgorithm.sip

@@ -43,6 +43,13 @@ class QgsProcessingAlgorithm
     virtual ~QgsProcessingAlgorithm();
 
 
+
+    virtual QgsProcessingAlgorithm *clone() const = 0 /Factory/;
+%Docstring
+ Clones the algorithm, returning a new copy for safe use in background threads.
+ :rtype: QgsProcessingAlgorithm
+%End
+
     virtual QString name() const = 0;
 %Docstring
  Returns the algorithm name, used for identifying the algorithm. This string

python/core/processing/qgsprocessingmodelalgorithm.sip

@@ -588,6 +588,8 @@ Copies are protected to avoid slicing
 
     virtual QString asPythonCommand( const QVariantMap &parameters, QgsProcessingContext &context ) const;
 
+    virtual QgsProcessingModelAlgorithm *clone() const /Factory/;
+
 
     void setName( const QString &name );
 %Docstring

python/plugins/processing/modeler/ModelerDialog.py

@@ -237,9 +237,9 @@ class ModelerDialog(BASE, WIDGET):
         self.mActionRun.triggered.connect(self.runModel)
 
         if model is not None:
-            self.model = model
+            self.model = model.clone()
-            self.textGroup.setText(model.group())
+            self.textGroup.setText(self.model.group())
-            self.textName.setText(model.displayName())
+            self.textName.setText(self.model.displayName())
             self.repaintModel()
 
         else:
@@ -440,7 +440,7 @@ class ModelerDialog(BASE, WIDGET):
             return
         self.model.setName(str(self.textName.text()))
         self.model.setGroup(str(self.textGroup.text()))
-        if self.model.sourceFilePath() is not None and not saveAs:
+        if self.model.sourceFilePath() and not saveAs:
             filename = self.model.sourceFilePath()
         else:
             filename, filter = QFileDialog.getSaveFileName(self,

src/core/processing/qgsnativealgorithms.cpp

@@ -84,6 +84,11 @@ QString QgsCentroidAlgorithm::shortHelpString() const
                       "The attributes associated to each point in the output layer are the same ones associated to the original features." );
 }
 
+QgsCentroidAlgorithm *QgsCentroidAlgorithm::clone() const
+{
+  return new QgsCentroidAlgorithm();
+}
+
 QVariantMap QgsCentroidAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback ) const
 {
   std::unique_ptr< QgsFeatureSource > source( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
@@ -159,6 +164,11 @@ QString QgsBufferAlgorithm::shortHelpString() const
                       "The mitre limit parameter is only applicable for mitre join styles, and controls the maximum distance from the offset curve to use when creating a mitred join." );
 }
 
+QgsBufferAlgorithm *QgsBufferAlgorithm::clone() const
+{
+  return new QgsBufferAlgorithm();
+}
+
 QVariantMap QgsBufferAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback ) const
 {
   std::unique_ptr< QgsFeatureSource > source( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
@@ -263,6 +273,11 @@ QString QgsDissolveAlgorithm::shortHelpString() const
                       "In case the input is a polygon layer, common boundaries of adjacent polygons being dissolved will get erased." );
 }
 
+QgsDissolveAlgorithm *QgsDissolveAlgorithm::clone() const
+{
+  return new QgsDissolveAlgorithm();
+}
+
 QVariantMap QgsDissolveAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback ) const
 {
   std::unique_ptr< QgsFeatureSource > source( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
@@ -406,6 +421,11 @@ QString QgsClipAlgorithm::shortHelpString() const
                       "be manually updated." );
 }
 
+QgsClipAlgorithm *QgsClipAlgorithm::clone() const
+{
+  return new QgsClipAlgorithm();
+}
+
 QVariantMap QgsClipAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback ) const
 {
   std::unique_ptr< QgsFeatureSource > featureSource( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
@@ -554,6 +574,11 @@ QString QgsTransformAlgorithm::shortHelpString() const
                       "Attributes are not modified by this algorithm." );
 }
 
+QgsTransformAlgorithm *QgsTransformAlgorithm::clone() const
+{
+  return new QgsTransformAlgorithm();
+}
+
 QVariantMap QgsTransformAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback ) const
 {
   std::unique_ptr< QgsFeatureSource > source( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
@@ -618,6 +643,11 @@ QString QgsSubdivideAlgorithm::shortHelpString() const
                       "Curved geometries will be segmentized before subdivision." );
 }
 
+QgsSubdivideAlgorithm *QgsSubdivideAlgorithm::clone() const
+{
+  return new QgsSubdivideAlgorithm();
+}
+
 QVariantMap QgsSubdivideAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback ) const
 {
   std::unique_ptr< QgsFeatureSource > source( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
@@ -684,6 +714,11 @@ QString QgsMultipartToSinglepartAlgorithm::shortHelpString() const
                       "contain, and the same attributes are used for each of them." );
 }
 
+QgsMultipartToSinglepartAlgorithm *QgsMultipartToSinglepartAlgorithm::clone() const
+{
+  return new QgsMultipartToSinglepartAlgorithm();
+}
+
 QVariantMap QgsMultipartToSinglepartAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback ) const
 {
   std::unique_ptr< QgsFeatureSource > source( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
@@ -766,6 +801,11 @@ QString QgsExtractByExpressionAlgorithm::shortHelpString() const
                       "For more information about expressions see the <a href =\"{qgisdocs}/user_manual/working_with_vector/expression.html\">user manual</a>" );
 }
 
+QgsExtractByExpressionAlgorithm *QgsExtractByExpressionAlgorithm::clone() const
+{
+  return new QgsExtractByExpressionAlgorithm();
+}
+
 QVariantMap QgsExtractByExpressionAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback ) const
 {
   std::unique_ptr< QgsFeatureSource > source( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
@@ -892,6 +932,11 @@ QString QgsExtractByAttributeAlgorithm::shortHelpString() const
                       "of an attribute from the input layer." );
 }
 
+QgsExtractByAttributeAlgorithm *QgsExtractByAttributeAlgorithm::clone() const
+{
+  return new QgsExtractByAttributeAlgorithm();
+}
+
 QVariantMap QgsExtractByAttributeAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback ) const
 {
   std::unique_ptr< QgsFeatureSource > source( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );

src/core/processing/qgsnativealgorithms.h

@@ -60,6 +60,7 @@ class QgsCentroidAlgorithm : public QgsProcessingAlgorithm
     virtual QStringList tags() const override { return QObject::tr( "centroid,center,average,point,middle" ).split( ',' ); }
     QString group() const override { return QObject::tr( "Vector geometry tools" ); }
     QString shortHelpString() const override;
+    QgsCentroidAlgorithm *clone() const override SIP_FACTORY;
 
   protected:
 
@@ -83,6 +84,7 @@ class QgsTransformAlgorithm : public QgsProcessingAlgorithm
     virtual QStringList tags() const override { return QObject::tr( "transform,reproject,crs,srs,warp" ).split( ',' ); }
     QString group() const override { return QObject::tr( "Vector general tools" ); }
     QString shortHelpString() const override;
+    QgsTransformAlgorithm *clone() const override SIP_FACTORY;
 
   protected:
 
@@ -106,6 +108,7 @@ class QgsBufferAlgorithm : public QgsProcessingAlgorithm
     virtual QStringList tags() const override { return QObject::tr( "buffer,grow" ).split( ',' ); }
     QString group() const override { return QObject::tr( "Vector geometry tools" ); }
     QString shortHelpString() const override;
+    QgsBufferAlgorithm *clone() const override SIP_FACTORY;
 
   protected:
 
@@ -129,6 +132,7 @@ class QgsDissolveAlgorithm : public QgsProcessingAlgorithm
     virtual QStringList tags() const override { return QObject::tr( "dissolve,union,combine,collect" ).split( ',' ); }
     QString group() const override { return QObject::tr( "Vector geometry tools" ); }
     QString shortHelpString() const override;
+    QgsDissolveAlgorithm *clone() const override SIP_FACTORY;
 
   protected:
 
@@ -167,6 +171,7 @@ class QgsExtractByAttributeAlgorithm : public QgsProcessingAlgorithm
     virtual QStringList tags() const override { return QObject::tr( "extract,filter,attribute,value,contains,null,field" ).split( ',' ); }
     QString group() const override { return QObject::tr( "Vector selection tools" ); }
     QString shortHelpString() const override;
+    QgsExtractByAttributeAlgorithm *clone() const override SIP_FACTORY;
 
   protected:
 
@@ -190,6 +195,7 @@ class QgsExtractByExpressionAlgorithm : public QgsProcessingAlgorithm
     virtual QStringList tags() const override { return QObject::tr( "extract,filter,expression,field" ).split( ',' ); }
     QString group() const override { return QObject::tr( "Vector selection tools" ); }
     QString shortHelpString() const override;
+    QgsExtractByExpressionAlgorithm *clone() const override SIP_FACTORY;
 
   protected:
 
@@ -213,6 +219,7 @@ class QgsClipAlgorithm : public QgsProcessingAlgorithm
     virtual QStringList tags() const override { return QObject::tr( "clip,intersect,intersection,mask" ).split( ',' ); }
     QString group() const override { return QObject::tr( "Vector overlay tools" ); }
     QString shortHelpString() const override;
+    QgsClipAlgorithm *clone() const override SIP_FACTORY;
 
   protected:
 
@@ -237,6 +244,7 @@ class QgsSubdivideAlgorithm : public QgsProcessingAlgorithm
     virtual QStringList tags() const override { return QObject::tr( "subdivide,segmentize,split,tesselate" ).split( ',' ); }
     QString group() const override { return QObject::tr( "Vector geometry tools" ); }
     QString shortHelpString() const override;
+    QgsSubdivideAlgorithm *clone() const override SIP_FACTORY;
 
   protected:
 
@@ -260,6 +268,7 @@ class QgsMultipartToSinglepartAlgorithm : public QgsProcessingAlgorithm
     virtual QStringList tags() const override { return QObject::tr( "multi,single,multiple,split,dump" ).split( ',' ); }
     QString group() const override { return QObject::tr( "Vector geometry tools" ); }
     QString shortHelpString() const override;
+    QgsMultipartToSinglepartAlgorithm *clone() const override SIP_FACTORY;
 
   protected:
 

src/core/processing/qgsprocessingalgorithm.h

@@ -61,11 +61,17 @@ class CORE_EXPORT QgsProcessingAlgorithm
 
     virtual ~QgsProcessingAlgorithm();
 
-    //! Algorithms cannot be copied
+
+    //! Algorithms cannot be copied - clone() should be used instead
     QgsProcessingAlgorithm( const QgsProcessingAlgorithm &other ) = delete;
-    //! Algorithms cannot be copied
+    //! Algorithms cannot be copied- clone() should be used instead
     QgsProcessingAlgorithm &operator=( const QgsProcessingAlgorithm &other ) = delete;
 
+    /**
+     * Clones the algorithm, returning a new copy for safe use in background threads.
+     */
+    virtual QgsProcessingAlgorithm *clone() const = 0 SIP_FACTORY;
+
     /**
      * Returns the algorithm name, used for identifying the algorithm. This string
      * should be fixed for the algorithm, and must not be localised. The name should

src/core/processing/qgsprocessingmodelalgorithm.cpp

@@ -1101,6 +1101,13 @@ QString QgsProcessingModelAlgorithm::asPythonCommand( const QVariantMap &paramet
   return QgsProcessingAlgorithm::asPythonCommand( parameters, context );
 }
 
+QgsProcessingModelAlgorithm *QgsProcessingModelAlgorithm::clone() const
+{
+  QgsProcessingModelAlgorithm *alg = new QgsProcessingModelAlgorithm();
+  alg->loadVariant( toVariant() );
+  alg->setProvider( provider() );
+  return alg;
+}
 
 bool QgsProcessingModelAlgorithm::ChildParameterSource::operator==( const QgsProcessingModelAlgorithm::ChildParameterSource &other ) const
 {

src/core/processing/qgsprocessingmodelalgorithm.h

@@ -590,6 +590,7 @@ class CORE_EXPORT QgsProcessingModelAlgorithm : public QgsProcessingAlgorithm
 
     bool canExecute( QString *errorMessage SIP_OUT = nullptr ) const override;
     QString asPythonCommand( const QVariantMap &parameters, QgsProcessingContext &context ) const override;
+    QgsProcessingModelAlgorithm *clone() const override SIP_FACTORY;
 
     /**
      * Sets the model \a name.

tests/src/core/testqgsprocessing.cpp

@@ -46,6 +46,7 @@ class DummyAlgorithm : public QgsProcessingAlgorithm
                                           QgsProcessingContext &, QgsProcessingFeedback * ) const override { return QVariantMap(); }
 
     virtual Flags flags() const override { return mFlags; }
+    DummyAlgorithm *clone() const override { return new DummyAlgorithm( name() ); }
 
     QString mName;