Allow specifying algorithm configuration when calling create

Author: nyalldawson

python/core/processing/qgsprocessingalgorithm.sip

@@ -47,13 +47,19 @@ class QgsProcessingAlgorithm
     virtual ~QgsProcessingAlgorithm();
 
 
-    QgsProcessingAlgorithm *create() const /Factory/;
+    QgsProcessingAlgorithm *create( const QVariantMap &configuration = QVariantMap() ) const /Factory/;
 %Docstring
  Creates a copy of the algorithm, ready for execution.
 
  This method returns a new, preinitialized copy of the algorithm, ready for
  executing.
 
+ The ``configuration`` argument allows passing of a map of configuration settings
+ to the algorithm, allowing it to dynamically adjust its initialized parameters
+ and outputs according to this configuration. This is generally used only for
+ algorithms in a model, allowing them to adjust their behavior at run time
+ according to some user configuration.
+
 .. seealso:: initAlgorithm()
  :rtype: QgsProcessingAlgorithm
 %End

src/core/processing/qgsprocessingalgorithm.cpp

@@ -33,11 +33,11 @@ QgsProcessingAlgorithm::~QgsProcessingAlgorithm()
   qDeleteAll( mOutputs );
 }
 
-QgsProcessingAlgorithm *QgsProcessingAlgorithm::create() const
+QgsProcessingAlgorithm *QgsProcessingAlgorithm::create( const QVariantMap &configuration ) const
 {
   std::unique_ptr< QgsProcessingAlgorithm > creation( createInstance() );
   creation->setProvider( provider() );
-  creation->initAlgorithm();
+  creation->initAlgorithm( configuration );
   return creation.release();
 }
 

src/core/processing/qgsprocessingalgorithm.h

@@ -77,9 +77,15 @@ class CORE_EXPORT QgsProcessingAlgorithm
      * This method returns a new, preinitialized copy of the algorithm, ready for
      * executing.
      *
+     * The \a configuration argument allows passing of a map of configuration settings
+     * to the algorithm, allowing it to dynamically adjust its initialized parameters
+     * and outputs according to this configuration. This is generally used only for
+     * algorithms in a model, allowing them to adjust their behavior at run time
+     * according to some user configuration.
+     *
      * \see initAlgorithm()
      */
-    QgsProcessingAlgorithm *create() const SIP_FACTORY;
+    QgsProcessingAlgorithm *create( const QVariantMap &configuration = QVariantMap() ) const SIP_FACTORY;
 
     /**
      * Returns the algorithm name, used for identifying the algorithm. This string