[processing] Cleanup some layer/writer related handling

Ensure that layers created by QgsProcessingUtils::createFeatureSink
can always be retrieved using QgsProcessingUtils::mapLayerFromString

python/core/processing/qgsprocessingutils.sip

@@ -130,8 +130,7 @@ class QgsProcessingUtils
       const QgsFields &fields,
       QgsWkbTypes::Type geometryType,
       const QgsCoordinateReferenceSystem &crs,
-      QgsProcessingContext &context,
-      QgsVectorLayer **outputLayer /Out/ ) /PyName=createFeatureSink/;
+      QgsProcessingContext &context ) /PyName=createFeatureSink/;
 %Docstring
  Creates a feature sink ready for adding features. The ``destination`` specifies a destination
  URI for the resultant layer. It may be updated in place to reflect the actual destination
@@ -142,7 +141,7 @@ class QgsProcessingUtils
  If the ``encoding`` is not specified, the default encoding from the ``context`` will be used.
 
  If a layer is created for the feature sink, the layer will automatically be added to the ``context``'s
- temporary layer store, and the ``outputLayer`` argument updated to point at this newly created layer.
+ temporary layer store.
 
 .. note::
 

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

@@ -86,7 +86,7 @@ def processAlgorithm(self, context, feedback):
         for current, i in enumerate(uniqueValues):
             fName = u'{0}_{1}.shp'.format(baseName, str(i).strip())
 
-            writer, dest, _layer = QgsProcessingUtils.createFeatureSink(fName, None, fields, geomType, crs, context)
+            writer, dest = QgsProcessingUtils.createFeatureSink(fName, None, fields, geomType, crs, context)
             for f in QgsProcessingUtils.getFeatures(layer, context):
                 if f[fieldName] == i:
                     writer.addFeature(f)

python/plugins/processing/algs/qgis/scripts/Number_of_unique_values_in_classes.py

@@ -10,8 +10,8 @@
 layer = QgsProcessingUtils.mapLayerFromString(input, context)
 fields = layer.fields()
 fields.append(QgsField('UNIQ_COUNT', QVariant.Int))
-writer, writer_dest, writer_layer = QgsProcessingUtils.createFeatureSink(N_unique_values, None, fields, layer.wkbType(), layer.crs(),
-                                                                         context)
+writer, writer_dest = QgsProcessingUtils.createFeatureSink(N_unique_values, None, fields, layer.wkbType(), layer.crs(),
+                                                           context)
 
 class_field_index = layer.fields().lookupField(class_field)
 value_field_index = layer.fields().lookupField(value_field)

python/plugins/processing/core/outputs.py

@@ -385,8 +385,7 @@ def getVectorWriter(self, fields, geomType, crs, context):
             settings = QgsSettings()
             self.encoding = settings.value('/Processing/encoding', 'System', str)
 
-        w, w_dest, w_layer = QgsProcessingUtils.createFeatureSink(self.value, self.encoding, fields, geomType, crs, context)
-        self.layer = w_layer
+        w, w_dest = QgsProcessingUtils.createFeatureSink(self.value, self.encoding, fields, geomType, crs, context)
         self.value = w_dest
         return w
 

python/plugins/processing/gui/Postprocessing.py

@@ -61,11 +61,10 @@ def handleAlgorithmResults(alg, context, feedback=None, showResults=True):
             continue
         if isinstance(out, (OutputRaster, OutputVector, OutputTable)):
             try:
-                if hasattr(out, "layer") and out.layer is not None:
-                    out.layer.setName(out.description)
-                    QgsProject.instance().addMapLayer(context.temporaryLayerStore().takeMapLayer(out.layer))
-                    # temporary hack to work around mutable outputs
-                    out.layer = None
+                layer = QgsProcessingUtils.mapLayerFromString(out.value, context)
+                if layer:
+                    layer.setName(out.description)
+                    QgsProject.instance().addMapLayer(context.temporaryLayerStore().takeMapLayer(layer))
                 else:
                     if ProcessingConfig.getSetting(
                             ProcessingConfig.USE_FILENAME_AS_LAYER_NAME):

python/plugins/processing/tests/testdata/scripts/centroids.py

@@ -8,7 +8,7 @@
 layer = QgsProcessingUtils.mapLayerFromString(INPUT_LAYER, context)
 fields = layer.fields()
 
-writer, writer_dest, writer_layer = QgsProcessingUtils.createFeatureSink(OUTPUT_LAYER, 'utf-8', fields, QgsWkbTypes.Point, layer.crs(),
+writer, writer_dest = QgsProcessingUtils.createFeatureSink(OUTPUT_LAYER, 'utf-8', fields, QgsWkbTypes.Point, layer.crs(),
                                                                          context)
 
 features = QgsProcessingUtils.getFeatures(layer, context)

src/core/processing/qgsprocessingutils.cpp

@@ -328,12 +328,10 @@ void parseDestinationString( QString &destination, QString &providerKey, QString
   }
 }
 
-QgsFeatureSink *QgsProcessingUtils::createFeatureSink( QString &destination, const QString &encoding, const QgsFields &fields, QgsWkbTypes::Type geometryType, const QgsCoordinateReferenceSystem &crs, QgsProcessingContext &context, QgsVectorLayer *&outputLayer )
+QgsFeatureSink *QgsProcessingUtils::createFeatureSink( QString &destination, const QString &encoding, const QgsFields &fields, QgsWkbTypes::Type geometryType, const QgsCoordinateReferenceSystem &crs, QgsProcessingContext &context )
 {
-  outputLayer = nullptr;
-  QgsVectorLayer *layer = nullptr;
-
   QString destEncoding = encoding;
+  QgsVectorLayer *layer = nullptr;
   if ( destEncoding.isEmpty() )
   {
     // no destination encoding specified, use default
@@ -344,8 +342,6 @@ QgsFeatureSink *QgsProcessingUtils::createFeatureSink( QString &destination, con
   {
     // memory provider cannot be used with QgsVectorLayerImport - so create layer manually
     layer = QgsMemoryProviderUtils::createMemoryLayer( destination, fields, geometryType, crs );
-    if ( layer && layer->isValid() )
-      destination = layer->id();
   }
   else
   {
@@ -376,6 +372,7 @@ QgsFeatureSink *QgsProcessingUtils::createFeatureSink( QString &destination, con
           return nullptr;
       }
 
+      // use destination string as layer name (eg "postgis:..." )
       layer = new QgsVectorLayer( uri, destination, providerKey );
     }
   }
@@ -389,19 +386,18 @@ QgsFeatureSink *QgsProcessingUtils::createFeatureSink( QString &destination, con
     return nullptr;
   }
 
+  // update destination to layer ID
+  destination = layer->id();
+
   context.temporaryLayerStore()->addMapLayer( layer );
 
-  outputLayer = layer;
   // this is a factory, so we need to return a proxy
   return new QgsProxyFeatureSink( layer->dataProvider() );
 }
 
-void QgsProcessingUtils::createFeatureSinkPython( QgsFeatureSink **sink, QString &destination, const QString &encoding, const QgsFields &fields, QgsWkbTypes::Type geometryType, const QgsCoordinateReferenceSystem &crs, QgsProcessingContext &context, QgsVectorLayer **outputLayer )
+void QgsProcessingUtils::createFeatureSinkPython( QgsFeatureSink **sink, QString &destination, const QString &encoding, const QgsFields &fields, QgsWkbTypes::Type geometryType, const QgsCoordinateReferenceSystem &crs, QgsProcessingContext &context )
 {
-  QgsVectorLayer *layer = nullptr;
-  *sink = createFeatureSink( destination, encoding, fields, geometryType, crs, context, layer );
-  if ( outputLayer )
-    *outputLayer = layer;
+  *sink = createFeatureSink( destination, encoding, fields, geometryType, crs, context );
 }
 
 

src/core/processing/qgsprocessingutils.h

@@ -141,7 +141,7 @@ class CORE_EXPORT QgsProcessingUtils
      * If the \a encoding is not specified, the default encoding from the \a context will be used.
      *
      * If a layer is created for the feature sink, the layer will automatically be added to the \a context's
-     * temporary layer store, and the \a outputLayer argument updated to point at this newly created layer.
+     * temporary layer store.
      *
      * The caller takes responsibility for deleting the returned sink.
      */
@@ -152,8 +152,7 @@ class CORE_EXPORT QgsProcessingUtils
       const QgsFields &fields,
       QgsWkbTypes::Type geometryType,
       const QgsCoordinateReferenceSystem &crs,
-      QgsProcessingContext &context,
-      QgsVectorLayer *&outputLayer ) SIP_FACTORY;
+      QgsProcessingContext &context ) SIP_FACTORY;
 #endif
 
     /**
@@ -166,7 +165,7 @@ class CORE_EXPORT QgsProcessingUtils
      * If the \a encoding is not specified, the default encoding from the \a context will be used.
      *
      * If a layer is created for the feature sink, the layer will automatically be added to the \a context's
-     * temporary layer store, and the \a outputLayer argument updated to point at this newly created layer.
+     * temporary layer store.
      *
      * \note this version of the createFeatureSink() function has an API designed around use from the
      * SIP bindings. c++ code should call the other createFeatureSink() version.
@@ -179,8 +178,7 @@ class CORE_EXPORT QgsProcessingUtils
       const QgsFields &fields,
       QgsWkbTypes::Type geometryType,
       const QgsCoordinateReferenceSystem &crs,
-      QgsProcessingContext &context,
-      QgsVectorLayer **outputLayer SIP_OUT ) SIP_PYNAME( createFeatureSink );
+      QgsProcessingContext &context ) SIP_PYNAME( createFeatureSink );
 
 
   private:

tests/src/core/testqgsprocessing.cpp

@@ -748,8 +748,9 @@ void TestQgsProcessing::createFeatureSink()
   QgsVectorLayer *layer = nullptr;
 
   // should create a memory layer
-  QgsFeatureSink *sink = QgsProcessingUtils::createFeatureSink( destination, QString(), QgsFields(), QgsWkbTypes::Point, QgsCoordinateReferenceSystem(), context, layer );
+  QgsFeatureSink *sink = QgsProcessingUtils::createFeatureSink( destination, QString(), QgsFields(), QgsWkbTypes::Point, QgsCoordinateReferenceSystem(), context );
   QVERIFY( sink );
+  layer = qobject_cast< QgsVectorLayer *>( QgsProcessingUtils::mapLayerFromString( destination, context, false ) );
   QVERIFY( layer );
   QCOMPARE( static_cast< QgsProxyFeatureSink *>( sink )->destinationSink(), layer->dataProvider() );
   QCOMPARE( layer->dataProvider()->name(), QStringLiteral( "memory" ) );
@@ -765,8 +766,9 @@ void TestQgsProcessing::createFeatureSink()
 
   // specific memory layer output
   destination = QStringLiteral( "memory:mylayer" );
-  sink = QgsProcessingUtils::createFeatureSink( destination, QString(), QgsFields(), QgsWkbTypes::Point, QgsCoordinateReferenceSystem(), context, layer );
+  sink = QgsProcessingUtils::createFeatureSink( destination, QString(), QgsFields(), QgsWkbTypes::Point, QgsCoordinateReferenceSystem(), context );
   QVERIFY( sink );
+  layer = qobject_cast< QgsVectorLayer *>( QgsProcessingUtils::mapLayerFromString( destination, context, false ) );
   QVERIFY( layer );
   QCOMPARE( static_cast< QgsProxyFeatureSink *>( sink )->destinationSink(), layer->dataProvider() );
   QCOMPARE( layer->dataProvider()->name(), QStringLiteral( "memory" ) );
@@ -784,8 +786,9 @@ void TestQgsProcessing::createFeatureSink()
   destination = QStringLiteral( "memory:mylayer" );
   QgsFields fields;
   fields.append( QgsField( QStringLiteral( "my_field" ), QVariant::String, QString(), 100 ) );
-  sink = QgsProcessingUtils::createFeatureSink( destination, QString(), fields, QgsWkbTypes::PointZM, QgsCoordinateReferenceSystem::fromEpsgId( 3111 ), context, layer );
+  sink = QgsProcessingUtils::createFeatureSink( destination, QString(), fields, QgsWkbTypes::PointZM, QgsCoordinateReferenceSystem::fromEpsgId( 3111 ), context );
   QVERIFY( sink );
+  layer = qobject_cast< QgsVectorLayer *>( QgsProcessingUtils::mapLayerFromString( destination, context, false ) );
   QVERIFY( layer );
   QCOMPARE( static_cast< QgsProxyFeatureSink *>( sink )->destinationSink(), layer->dataProvider() );
   QCOMPARE( layer->dataProvider()->name(), QStringLiteral( "memory" ) );
@@ -807,16 +810,15 @@ void TestQgsProcessing::createFeatureSink()
   // non memory layer output
   destination = QDir::tempPath() + "/create_feature_sink.tab";
   QString prevDest = destination;
-  sink = QgsProcessingUtils::createFeatureSink( destination, QString(), fields, QgsWkbTypes::Polygon, QgsCoordinateReferenceSystem::fromEpsgId( 3111 ), context, layer );
+  sink = QgsProcessingUtils::createFeatureSink( destination, QString(), fields, QgsWkbTypes::Polygon, QgsCoordinateReferenceSystem::fromEpsgId( 3111 ), context );
   QVERIFY( sink );
   f = QgsFeature( fields );
   f.setGeometry( QgsGeometry::fromWkt( QStringLiteral( "Polygon((0 0, 0 1, 1 1, 1 0, 0 0 ))" ) ) );
   f.setAttributes( QgsAttributes() << "val" );
   QVERIFY( sink->addFeature( f ) );
-  QVERIFY( !layer );
   QCOMPARE( destination, prevDest );
   delete sink;
-  layer = new QgsVectorLayer( destination, "test_layer", "ogr" );
+  layer = qobject_cast< QgsVectorLayer *>( QgsProcessingUtils::mapLayerFromString( destination, context, true ) );
   QVERIFY( layer->isValid() );
   QCOMPARE( layer->crs().authid(), QStringLiteral( "EPSG:3111" ) );
   QCOMPARE( layer->fields().size(), 1 );
@@ -829,14 +831,14 @@ void TestQgsProcessing::createFeatureSink()
   // no extension, should default to shp
   destination = QDir::tempPath() + "/create_feature_sink2";
   prevDest = QDir::tempPath() + "/create_feature_sink2.shp";
-  sink = QgsProcessingUtils::createFeatureSink( destination, QString(), fields, QgsWkbTypes::Point25D, QgsCoordinateReferenceSystem::fromEpsgId( 3111 ), context, layer );
+  sink = QgsProcessingUtils::createFeatureSink( destination, QString(), fields, QgsWkbTypes::Point25D, QgsCoordinateReferenceSystem::fromEpsgId( 3111 ), context );
   QVERIFY( sink );
   f.setGeometry( QgsGeometry::fromWkt( QStringLiteral( "PointZ(1 2 3)" ) ) );
   QVERIFY( sink->addFeature( f ) );
   QVERIFY( !layer );
   QCOMPARE( destination, prevDest );
   delete sink;
-  layer = new QgsVectorLayer( destination, "test_layer", "ogr" );
+  layer = qobject_cast< QgsVectorLayer *>( QgsProcessingUtils::mapLayerFromString( destination, context, true ) );
   QCOMPARE( layer->wkbType(), QgsWkbTypes::Point25D );
   QCOMPARE( layer->crs().authid(), QStringLiteral( "EPSG:3111" ) );
   QCOMPARE( layer->fields().size(), 1 );