Split QgsProcessingAlgorithm::create into non virtual-create

and pure virtual createInstance

Allows us to add logic which always need applying within
create(), leaving createInstance() free to just return a
raw new instance of the class

python/core/processing/models/qgsprocessingmodelalgorithm.sip

@@ -46,7 +46,7 @@ class QgsProcessingModelAlgorithm : QgsProcessingAlgorithm
 
     virtual QString asPythonCommand( const QVariantMap &parameters, QgsProcessingContext &context ) const;
 
-    virtual QgsProcessingModelAlgorithm *create() const /Factory/;
+    virtual QgsProcessingModelAlgorithm *createInstance() const /Factory/;
 
 
     void setName( const QString &name );

python/core/processing/qgsprocessingalgorithm.sip

@@ -43,8 +43,7 @@ class QgsProcessingAlgorithm
     virtual ~QgsProcessingAlgorithm();
 
 
-
-    virtual QgsProcessingAlgorithm *create() const = 0 /Factory/;
+    QgsProcessingAlgorithm *create() const /Factory/;
 %Docstring
  Creates a copy of the algorithm, ready for execution.
  :rtype: QgsProcessingAlgorithm
@@ -332,6 +331,14 @@ class QgsProcessingAlgorithm
 
   protected:
 
+    virtual QgsProcessingAlgorithm *createInstance() const = 0 /Factory/;
+%Docstring
+ Creates a new instance of the algorithm class.
+
+ This method should return a 'pristine' instance of the algorithm class.
+ :rtype: QgsProcessingAlgorithm
+%End
+
     bool addParameter( QgsProcessingParameterDefinition *parameterDefinition /Transfer/ );
 %Docstring
  Adds a parameter ``definition`` to the algorithm. Ownership of the definition is transferred to the algorithm.

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

@@ -48,5 +48,5 @@ class QgisAlgorithm(QgsProcessingAlgorithm):
             context = self.__class__.__name__
         return string, QCoreApplication.translate(context, string)
 
-    def create(self):
+    def createInstance(self):
         return type(self)()

python/plugins/processing/script/ScriptAlgorithm.py

@@ -79,7 +79,7 @@ class ScriptAlgorithm(QgsProcessingAlgorithm):
         self.cleaned_script = None
         self.results = {}
 
-    def create(self):
+    def createInstance(self):
         return ScriptAlgorithm(self.descriptionFile)
 
     def icon(self):

python/plugins/processing/tests/QgisAlgorithmsTest.py

@@ -48,7 +48,7 @@ class TestAlg(QgsProcessingAlgorithm):
     def displayName(self):
         return 'testalg'
 
-    def create(self):
+    def createInstance(self):
         return TestAlg()
 
     def processAlgorithm(self, parameters, context, feedback):

src/core/processing/models/qgsprocessingmodelalgorithm.cpp

@@ -1100,7 +1100,7 @@ QString QgsProcessingModelAlgorithm::asPythonCommand( const QVariantMap &paramet
   return QgsProcessingAlgorithm::asPythonCommand( parameters, context );
 }
 
-QgsProcessingModelAlgorithm *QgsProcessingModelAlgorithm::create() const
+QgsProcessingAlgorithm *QgsProcessingModelAlgorithm::createInstance() const
 {
   QgsProcessingModelAlgorithm *alg = new QgsProcessingModelAlgorithm();
   alg->loadVariant( toVariant() );

src/core/processing/models/qgsprocessingmodelalgorithm.h

@@ -52,7 +52,7 @@ 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 *create() const override SIP_FACTORY;
+    QgsProcessingAlgorithm *createInstance() const override SIP_FACTORY;
 
     /**
      * Sets the model \a name.

src/core/processing/models/qgsprocessingmodelchildalgorithm.cpp

@@ -208,10 +208,6 @@ void QgsProcessingModelChildAlgorithm::setAlgorithmId( const QString &algorithmI
 {
   mAlgorithmId = algorithmId;
   mAlgorithm.reset( QgsApplication::processingRegistry()->createAlgorithmById( mAlgorithmId ) );
-  if ( mAlgorithm )
-  {
-    mAlgorithm->init( QVariantMap() );
-  }
 }
 
 ///@endcond

src/core/processing/qgsnativealgorithms.cpp

@@ -84,7 +84,7 @@ 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::create() const
+QgsCentroidAlgorithm *QgsCentroidAlgorithm::createInstance() const
 {
   return new QgsCentroidAlgorithm();
 }
@@ -164,7 +164,7 @@ 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::create() const
+QgsBufferAlgorithm *QgsBufferAlgorithm::createInstance() const
 {
   return new QgsBufferAlgorithm();
 }
@@ -273,7 +273,7 @@ QString QgsDissolveAlgorithm::shortHelpString() const
                       "In case the input is a polygon layer, common boundaries of adjacent polygons being dissolved will get erased." );
 }
 
-QgsDissolveAlgorithm *QgsDissolveAlgorithm::create() const
+QgsDissolveAlgorithm *QgsDissolveAlgorithm::createInstance() const
 {
   return new QgsDissolveAlgorithm();
 }
@@ -430,7 +430,7 @@ QString QgsClipAlgorithm::shortHelpString() const
                       "be manually updated." );
 }
 
-QgsClipAlgorithm *QgsClipAlgorithm::create() const
+QgsClipAlgorithm *QgsClipAlgorithm::createInstance() const
 {
   return new QgsClipAlgorithm();
 }
@@ -583,7 +583,7 @@ QString QgsTransformAlgorithm::shortHelpString() const
                       "Attributes are not modified by this algorithm." );
 }
 
-QgsTransformAlgorithm *QgsTransformAlgorithm::create() const
+QgsTransformAlgorithm *QgsTransformAlgorithm::createInstance() const
 {
   return new QgsTransformAlgorithm();
 }
@@ -652,7 +652,7 @@ QString QgsSubdivideAlgorithm::shortHelpString() const
                       "Curved geometries will be segmentized before subdivision." );
 }
 
-QgsSubdivideAlgorithm *QgsSubdivideAlgorithm::create() const
+QgsSubdivideAlgorithm *QgsSubdivideAlgorithm::createInstance() const
 {
   return new QgsSubdivideAlgorithm();
 }
@@ -723,7 +723,7 @@ QString QgsMultipartToSinglepartAlgorithm::shortHelpString() const
                       "contain, and the same attributes are used for each of them." );
 }
 
-QgsMultipartToSinglepartAlgorithm *QgsMultipartToSinglepartAlgorithm::create() const
+QgsMultipartToSinglepartAlgorithm *QgsMultipartToSinglepartAlgorithm::createInstance() const
 {
   return new QgsMultipartToSinglepartAlgorithm();
 }
@@ -810,7 +810,7 @@ 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::create() const
+QgsExtractByExpressionAlgorithm *QgsExtractByExpressionAlgorithm::createInstance() const
 {
   return new QgsExtractByExpressionAlgorithm();
 }
@@ -941,7 +941,7 @@ QString QgsExtractByAttributeAlgorithm::shortHelpString() const
                       "of an attribute from the input layer." );
 }
 
-QgsExtractByAttributeAlgorithm *QgsExtractByAttributeAlgorithm::create() const
+QgsExtractByAttributeAlgorithm *QgsExtractByAttributeAlgorithm::createInstance() const
 {
   return new QgsExtractByAttributeAlgorithm();
 }

src/core/processing/qgsnativealgorithms.h

@@ -60,7 +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 *create() const override SIP_FACTORY;
+    QgsCentroidAlgorithm *createInstance() const override SIP_FACTORY;
 
   protected:
 
@@ -84,7 +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 *create() const override SIP_FACTORY;
+    QgsTransformAlgorithm *createInstance() const override SIP_FACTORY;
 
   protected:
 
@@ -108,7 +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 *create() const override SIP_FACTORY;
+    QgsBufferAlgorithm *createInstance() const override SIP_FACTORY;
 
   protected:
 
@@ -132,7 +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 *create() const override SIP_FACTORY;
+    QgsDissolveAlgorithm *createInstance() const override SIP_FACTORY;
 
   protected:
 
@@ -171,7 +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 *create() const override SIP_FACTORY;
+    QgsExtractByAttributeAlgorithm *createInstance() const override SIP_FACTORY;
 
   protected:
 
@@ -195,7 +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 *create() const override SIP_FACTORY;
+    QgsExtractByExpressionAlgorithm *createInstance() const override SIP_FACTORY;
 
   protected:
 
@@ -219,7 +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 *create() const override SIP_FACTORY;
+    QgsClipAlgorithm *createInstance() const override SIP_FACTORY;
 
   protected:
 
@@ -244,7 +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 *create() const override SIP_FACTORY;
+    QgsSubdivideAlgorithm *createInstance() const override SIP_FACTORY;
 
   protected:
 
@@ -268,7 +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 *create() const override SIP_FACTORY;
+    QgsMultipartToSinglepartAlgorithm *createInstance() const override SIP_FACTORY;
 
   protected:
 

src/core/processing/qgsprocessingalgorithm.cpp

@@ -33,6 +33,13 @@ QgsProcessingAlgorithm::~QgsProcessingAlgorithm()
   qDeleteAll( mOutputs );
 }
 
+QgsProcessingAlgorithm *QgsProcessingAlgorithm::create() const
+{
+  std::unique_ptr< QgsProcessingAlgorithm > creation( createInstance() );
+  creation->setProvider( provider() );
+  return creation.release();
+}
+
 QString QgsProcessingAlgorithm::id() const
 {
   if ( mProvider )

src/core/processing/qgsprocessingalgorithm.h

@@ -70,7 +70,7 @@ class CORE_EXPORT QgsProcessingAlgorithm
     /**
      * Creates a copy of the algorithm, ready for execution.
      */
-    virtual QgsProcessingAlgorithm *create() const = 0 SIP_FACTORY;
+    QgsProcessingAlgorithm *create() const SIP_FACTORY;
 
     /**
      * Returns the algorithm name, used for identifying the algorithm. This string
@@ -317,6 +317,13 @@ class CORE_EXPORT QgsProcessingAlgorithm
 
   protected:
 
+    /**
+     * Creates a new instance of the algorithm class.
+     *
+     * This method should return a 'pristine' instance of the algorithm class.
+     */
+    virtual QgsProcessingAlgorithm *createInstance() const = 0 SIP_FACTORY;
+
     /**
      * Adds a parameter \a definition to the algorithm. Ownership of the definition is transferred to the algorithm.
      * Returns true if parameter could be successfully added, or false if the parameter could not be added (e.g.

tests/src/core/testqgsprocessing.cpp

@@ -45,7 +45,7 @@ class DummyAlgorithm : public QgsProcessingAlgorithm
     QVariantMap processAlgorithm( const QVariantMap &, QgsProcessingContext &, QgsProcessingFeedback * ) override { return QVariantMap(); }
 
     virtual Flags flags() const override { return mFlags; }
-    DummyAlgorithm *create() const override { return new DummyAlgorithm( name() ); }
+    DummyAlgorithm *createInstance() const override { return new DummyAlgorithm( name() ); }
 
     QString mName;
 
@@ -334,6 +334,7 @@ class TestQgsProcessing: public QObject
     void modelAcceptableValues();
     void tempUtils();
     void convertCompatible();
+    void create();
 
   private:
 
@@ -5126,5 +5127,16 @@ void TestQgsProcessing::convertCompatible()
   QVERIFY( out.startsWith( QgsProcessingUtils::tempFolder() ) );
 }
 
+void TestQgsProcessing::create()
+{
+  DummyAlgorithm alg( QStringLiteral( "test" ) );
+  DummyProvider p( QStringLiteral( "test_provider" ) );
+  alg.setProvider( &p );
+
+  std::unique_ptr< QgsProcessingAlgorithm > newInstance( alg.create() );
+  QVERIFY( newInstance.get() );
+  QCOMPARE( newInstance->provider(), &p );
+}
+
 QGSTEST_MAIN( TestQgsProcessing )
 #include "testqgsprocessing.moc"