Add prepareSource method

python/core/auto_generated/processing/qgsprocessingalgorithm.sip.in

@@ -984,6 +984,13 @@ checks based on the geometry type of the layer.
 
 :return: true if the algorithm supports in-place editing
 
+.. versionadded:: 3.4
+%End
+
+    void prepareSource( const QVariantMap &parameters, QgsProcessingContext &context );
+%Docstring
+Read the source from ``parameters`` and ``context`` and set it
+
 .. versionadded:: 3.4
 %End
 

src/analysis/processing/qgsalgorithmtransform.cpp

@@ -79,6 +79,7 @@ QgsTransformAlgorithm *QgsTransformAlgorithm::createInstance() const
 
 bool QgsTransformAlgorithm::prepareAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback * )
 {
+  prepareSource( parameters, context );
   mDestCrs = parameterAsCrs( parameters, QStringLiteral( "TARGET_CRS" ), context );
   mTransformContext = context.project() ? context.project()->transformContext() : QgsCoordinateTransformContext();
   return true;

src/core/processing/qgsprocessingalgorithm.cpp

@@ -768,6 +768,7 @@ bool QgsProcessingAlgorithm::supportInPlaceEdit( const QgsVectorLayer *layer ) c
   return false;
 }
 
+
 bool QgsProcessingAlgorithm::createAutoOutputForParameter( QgsProcessingParameterDefinition *parameter )
 {
   if ( !parameter->isDestination() )
@@ -852,10 +853,7 @@ QgsCoordinateReferenceSystem QgsProcessingFeatureBasedAlgorithm::sourceCrs() con
 
 QVariantMap QgsProcessingFeatureBasedAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
 {
-  mSource.reset( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
-  if ( !mSource )
-    throw QgsProcessingException( invalidSourceError( parameters, QStringLiteral( "INPUT" ) ) );
-
+  prepareSource( parameters, context );
   QString dest;
   std::unique_ptr< QgsFeatureSink > sink( parameterAsSink( parameters, QStringLiteral( "OUTPUT" ), context, dest,
                                           outputFields( mSource->fields() ),
@@ -933,3 +931,13 @@ bool QgsProcessingFeatureBasedAlgorithm::supportInPlaceEdit( const QgsVectorLaye
   return true;
 }
 
+void QgsProcessingFeatureBasedAlgorithm::prepareSource( const QVariantMap &parameters, QgsProcessingContext &context )
+{
+  if ( ! mSource )
+  {
+    mSource.reset( parameterAsSource( parameters, QStringLiteral( "INPUT" ), context ) );
+    if ( !mSource )
+      throw QgsProcessingException( invalidSourceError( parameters, QStringLiteral( "INPUT" ) ) );
+  }
+}
+

src/core/processing/qgsprocessingalgorithm.h

@@ -826,6 +826,7 @@ class CORE_EXPORT QgsProcessingAlgorithm
 
     bool createAutoOutputForParameter( QgsProcessingParameterDefinition *parameter );
 
+
     friend class QgsProcessingProvider;
     friend class TestQgsProcessing;
     friend class QgsProcessingModelAlgorithm;
@@ -990,6 +991,13 @@ class CORE_EXPORT QgsProcessingFeatureBasedAlgorithm : public QgsProcessingAlgor
      */
     virtual bool supportInPlaceEdit( const QgsVectorLayer *layer ) const override;
 
+    /**
+     * Read the source from \a parameters and \a context and set it
+     *
+     * \since QGIS 3.4
+     */
+    void prepareSource( const QVariantMap &parameters, QgsProcessingContext &context );
+
   private:
 
     std::unique_ptr< QgsProcessingFeatureSource > mSource;

tests/src/python/test_qgsprocessinginplace.py

@@ -88,6 +88,7 @@ def _alg_tester(self, alg_name, input_layer, parameters):
         context.setProject(QgsProject.instance())
         feedback = QgsProcessingFeedback()
 
+        input_layer.rollBack()
         with self.assertRaises(QgsProcessingException) as cm:
             execute_in_place_run(
                 alg, input_layer, parameters, context=context, feedback=feedback, raise_exceptions=True)
@@ -199,6 +200,26 @@ def test_arrayfeatures(self):
         # Check selected
         self.assertEqual(len(self.vl.selectedFeatureIds()), 3)
 
+    def test_reprojectlayer(self):
+        """Check that this runs correctly"""
+
+        old_count = self.vl.featureCount()
+
+        old_features, new_features = self._alg_tester(
+            'native:reprojectlayer',
+            self.vl,
+            {
+                'TARGET_CRS': 'EPSG:3857',
+            }
+        )
+
+        g = [f.geometry() for f in new_features][0]
+        self.assertAlmostEqual(g.get().x(), 1001875.4, 1)
+        self.assertAlmostEqual(g.get().y(), 5621521.5, 1)
+
+        # Check selected
+        self.assertEqual(self.vl.selectedFeatureIds(), [1])
+
     def _make_compatible_tester(self, feature_wkt, layer_wkb_name, attrs=[1], old_feature=None):
         fields = QgsFields()
         wkb_type = getattr(QgsWkbTypes, layer_wkb_name)