Model child algorithms store a copy of the algorithm itself

Instead of always retrieving it from the registry

python/core/processing/models/qgsprocessingmodelchildalgorithm.sip

@@ -29,6 +29,8 @@ class QgsProcessingModelChildAlgorithm : QgsProcessingModelComponent
  should be set to a QgsProcessingAlgorithm algorithm ID.
 %End
 
+    QgsProcessingModelChildAlgorithm( const QgsProcessingModelChildAlgorithm &other );
+
     QString childId() const;
 %Docstring
  Returns the child algorithm's unique ID string, used the identify

src/core/processing/models/qgsprocessingmodelalgorithm.cpp

@@ -1031,7 +1031,7 @@ QSet<QString> QgsProcessingModelAlgorithm::dependentChildAlgorithms( const QStri
 
 void QgsProcessingModelAlgorithm::dependsOnChildAlgorithmsRecursive( const QString &childId, QSet< QString > &depends ) const
 {
-  QgsProcessingModelChildAlgorithm alg = mChildAlgorithms.value( childId );
+  const QgsProcessingModelChildAlgorithm &alg = mChildAlgorithms.value( childId );
 
   // add direct dependencies
   Q_FOREACH ( const QString &c, alg.dependencies() )

src/core/processing/models/qgsprocessingmodelchildalgorithm.cpp

@@ -23,14 +23,40 @@
 ///@cond NOT_STABLE
 
 QgsProcessingModelChildAlgorithm::QgsProcessingModelChildAlgorithm( const QString &algorithmId )
-  : mAlgorithmId( algorithmId )
 {
+  setAlgorithmId( algorithmId );
+}
 
+QgsProcessingModelChildAlgorithm::QgsProcessingModelChildAlgorithm( const QgsProcessingModelChildAlgorithm &other )
+  : QgsProcessingModelComponent( other )
+  , mId( other.mId )
+  , mParams( other.mParams )
+  , mModelOutputs( other.mModelOutputs )
+  , mActive( other.mActive )
+  , mDependencies( other.mDependencies )
+  , mParametersCollapsed( other.mParametersCollapsed )
+  , mOutputsCollapsed( other.mOutputsCollapsed )
+{
+  setAlgorithmId( other.algorithmId() );
+}
+
+QgsProcessingModelChildAlgorithm &QgsProcessingModelChildAlgorithm::operator=( const QgsProcessingModelChildAlgorithm &other )
+{
+  QgsProcessingModelComponent::operator =( other );
+  mId = other.mId;
+  setAlgorithmId( other.algorithmId() );
+  mParams = other.mParams;
+  mModelOutputs = other.mModelOutputs;
+  mActive = other.mActive;
+  mDependencies = other.mDependencies;
+  mParametersCollapsed = other.mParametersCollapsed;
+  mOutputsCollapsed = other.mOutputsCollapsed;
+  return *this;
 }
 
 const QgsProcessingAlgorithm *QgsProcessingModelChildAlgorithm::algorithm() const
 {
-  return QgsApplication::processingRegistry()->algorithmById( mAlgorithmId );
+  return mAlgorithm.get();
 }
 
 void QgsProcessingModelChildAlgorithm::setModelOutputs( const QMap<QString, QgsProcessingModelOutput> &modelOutputs )
@@ -86,7 +112,7 @@ bool QgsProcessingModelChildAlgorithm::loadVariant( const QVariant &child )
   QVariantMap map = child.toMap();
 
   mId = map.value( QStringLiteral( "id" ) ).toString();
-  mAlgorithmId = map.value( QStringLiteral( "alg_id" ) ).toString();
+  setAlgorithmId( map.value( QStringLiteral( "alg_id" ) ).toString() );
   mActive = map.value( QStringLiteral( "active" ) ).toBool();
   mDependencies = map.value( QStringLiteral( "dependencies" ) ).toStringList();
   mParametersCollapsed = map.value( QStringLiteral( "parameters_collapsed" ) ).toBool();
@@ -178,4 +204,14 @@ void QgsProcessingModelChildAlgorithm::generateChildId( const QgsProcessingModel
   mId = id;
 }
 
+void QgsProcessingModelChildAlgorithm::setAlgorithmId( const QString &algorithmId )
+{
+  mAlgorithmId = algorithmId;
+  mAlgorithm.reset( QgsApplication::processingRegistry()->createAlgorithmById( mAlgorithmId ) );
+  if ( mAlgorithm )
+  {
+    mAlgorithm->init( QVariantMap() );
+  }
+}
+
 ///@endcond

src/core/processing/models/qgsprocessingmodelchildalgorithm.h

@@ -23,6 +23,7 @@
 #include "qgsprocessingmodelcomponent.h"
 #include "qgsprocessingmodelchildparametersource.h"
 #include "qgsprocessingmodeloutput.h"
+#include <memory>
 
 class QgsProcessingModelAlgorithm;
 class QgsProcessingAlgorithm;
@@ -44,6 +45,9 @@ class CORE_EXPORT QgsProcessingModelChildAlgorithm : public QgsProcessingModelCo
      */
     QgsProcessingModelChildAlgorithm( const QString &algorithmId = QString() );
 
+    QgsProcessingModelChildAlgorithm( const QgsProcessingModelChildAlgorithm &other );
+    QgsProcessingModelChildAlgorithm &operator=( const QgsProcessingModelChildAlgorithm &other );
+
     /**
      * Returns the child algorithm's unique ID string, used the identify
      * this child algorithm within its parent model.
@@ -81,7 +85,7 @@ class CORE_EXPORT QgsProcessingModelChildAlgorithm : public QgsProcessingModelCo
      * \see algorithm()
      * \see algorithmId()
      */
-    void setAlgorithmId( const QString &algorithmId ) { mAlgorithmId = algorithmId; }
+    void setAlgorithmId( const QString &algorithmId );
 
     /**
      * Returns the underlying child algorithm, or a nullptr
@@ -231,6 +235,7 @@ class CORE_EXPORT QgsProcessingModelChildAlgorithm : public QgsProcessingModelCo
     QString mId;
 
     QString mAlgorithmId;
+    std::unique_ptr< QgsProcessingAlgorithm > mAlgorithm;
 
     //! A map of parameter sources. Keys are algorithm parameter names.
     QMap< QString, QgsProcessingModelChildParameterSources > mParams;
@@ -247,6 +252,7 @@ class CORE_EXPORT QgsProcessingModelChildAlgorithm : public QgsProcessingModelCo
     bool mParametersCollapsed = true;
     //! Whether list of outputs should be collapsed in the graphical modeller
     bool mOutputsCollapsed = true;
+
 };
 
 ///@endcond

src/core/processing/qgsprocessingalgorithm.h

@@ -62,10 +62,9 @@ class CORE_EXPORT QgsProcessingAlgorithm
 
     virtual ~QgsProcessingAlgorithm();
 
-
-    //! Algorithms cannot be copied - clone() should be used instead
+    //! Algorithms cannot be copied - create() should be used instead
     QgsProcessingAlgorithm( const QgsProcessingAlgorithm &other ) = delete;
-    //! Algorithms cannot be copied- clone() should be used instead
+    //! Algorithms cannot be copied- create() should be used instead
     QgsProcessingAlgorithm &operator=( const QgsProcessingAlgorithm &other ) = delete;
 
     /**