Create class for encapsulating settings relating to a feature source

input to a processing algorithm.

This allows parameter inputs to encapsulate extra information
relating to a feature source input, such as whether only
selected features from the source layer should be used.

python/core/processing/qgsprocessingparameters.sip

@@ -11,6 +11,40 @@
 
 
 
+
+class QgsProcessingFeatureSourceDefinition
+{
+%Docstring
+
+ Encapsulates settings relating to a feature source input to a processing algorithm.
+
+.. versionadded:: 3.0
+%End
+
+%TypeHeaderCode
+#include "qgsprocessingparameters.h"
+%End
+  public:
+
+    QgsProcessingFeatureSourceDefinition( const QVariant &source = QVariant(), bool selectedFeaturesOnly = false );
+%Docstring
+ Constructor for QgsProcessingFeatureSourceDefinition.
+%End
+
+    QVariant source;
+%Docstring
+ Source definition. Usually set to a source layer's ID or file name.
+%End
+
+    bool selectedFeaturesOnly;
+%Docstring
+ True if only selected features in the source should be used by algorithms.
+%End
+
+};
+
+
+
 class QgsProcessingFeatureSink
 {
 %Docstring
@@ -52,6 +86,7 @@ class QgsProcessingFeatureSink
 
 
 
+
 class QgsProcessingParameterDefinition
 {
 %Docstring

src/core/processing/qgsprocessingparameters.cpp

@@ -253,9 +253,31 @@ QgsFeatureSource *QgsProcessingParameters::parameterAsSource( const QgsProcessin
   if ( !definition )
     return nullptr;
 
-  QString layerRef = parameterAsString( definition, parameters, context );
-  if ( layerRef.isEmpty() )
+  QVariant val = parameters.value( definition->name() );
+
+  bool selectedFeaturesOnly = false;
+  if ( val.canConvert<QgsProcessingFeatureSourceDefinition>() )
+  {
+    // input is a QgsProcessingFeatureSourceDefinition - get extra properties from it
+    QgsProcessingFeatureSourceDefinition fromVar = qvariant_cast<QgsProcessingFeatureSourceDefinition>( val );
+    selectedFeaturesOnly = fromVar.selectedFeaturesOnly;
+    val = fromVar.source;
+  }
+
+  QString layerRef;
+  if ( val.canConvert<QgsProperty>() )
+  {
+    layerRef = val.value< QgsProperty >().valueAsString( context.expressionContext(), definition->defaultValue().toString() );
+  }
+  else if ( !val.isValid() || val.toString().isEmpty() )
+  {
+    // fall back to default
     layerRef = definition->defaultValue().toString();
+  }
+  else
+  {
+    layerRef = val.toString();
+  }
 
   if ( layerRef.isEmpty() )
     return nullptr;
@@ -264,7 +286,7 @@ QgsFeatureSource *QgsProcessingParameters::parameterAsSource( const QgsProcessin
   if ( !vl )
     return nullptr;
 
-  if ( context.flags() & QgsProcessingContext::UseSelectionIfPresent && vl->selectedFeatureCount() > 0 )
+  if ( selectedFeaturesOnly )
   {
     return new QgsProcessingFeatureSource( new QgsVectorLayerSelectedFeatureSource( vl ), context, true );
   }

src/core/processing/qgsprocessingparameters.h

@@ -31,6 +31,42 @@ class QgsVectorLayer;
 class QgsFeatureSink;
 class QgsFeatureSource;
 
+
+/**
+ * \class QgsProcessingFeatureSourceDefinition
+ * \ingroup core
+ *
+ * Encapsulates settings relating to a feature source input to a processing algorithm.
+ *
+ * \since QGIS 3.0
+ */
+
+class CORE_EXPORT QgsProcessingFeatureSourceDefinition
+{
+  public:
+
+    /**
+     * Constructor for QgsProcessingFeatureSourceDefinition.
+     */
+    QgsProcessingFeatureSourceDefinition( const QVariant &source = QVariant(), bool selectedFeaturesOnly = false )
+      : source( source )
+      , selectedFeaturesOnly( selectedFeaturesOnly )
+    {}
+
+    /**
+     * Source definition. Usually set to a source layer's ID or file name.
+     */
+    QVariant source;
+
+    /**
+     * True if only selected features in the source should be used by algorithms.
+     */
+    bool selectedFeaturesOnly;
+
+};
+
+Q_DECLARE_METATYPE( QgsProcessingFeatureSourceDefinition )
+
 /**
  * \class QgsProcessingFeatureSink
  * \ingroup core
@@ -73,6 +109,7 @@ Q_DECLARE_METATYPE( QgsProcessingFeatureSink )
 
 
 
+
 //
 // Parameter definitions
 //

tests/src/core/testqgsprocessing.cpp

@@ -217,6 +217,7 @@ class TestQgsProcessing: public QObject
     void parameterOutputVectorLayer();
     void checkParamValues();
     void combineLayerExtent();
+    void processingFeatureSource();
     void processingFeatureSink();
 
   private:
@@ -452,8 +453,6 @@ void TestQgsProcessing::context()
   context.setDefaultEncoding( "my_enc" );
   QCOMPARE( context.defaultEncoding(), QStringLiteral( "my_enc" ) );
 
-  context.setFlags( QgsProcessingContext::UseSelectionIfPresent );
-  QCOMPARE( context.flags(), QgsProcessingContext::UseSelectionIfPresent );
   context.setFlags( QgsProcessingContext::Flags( 0 ) );
   QCOMPARE( context.flags(), QgsProcessingContext::Flags( 0 ) );
 
@@ -695,9 +694,9 @@ void TestQgsProcessing::features()
     return ids;
   };
 
-  QgsProcessingParameterDefinition *def = new QgsProcessingParameterString( QStringLiteral( "string" ) );
+  QgsProcessingParameterDefinition *def = new QgsProcessingParameterString( QStringLiteral( "layer" ) );
   QVariantMap params;
-  params.insert( QStringLiteral( "string" ), layer->id() );
+  params.insert( QStringLiteral( "layer" ), layer->id() );
 
   std::unique_ptr< QgsFeatureSource > source( QgsProcessingParameters::parameterAsSource( def, params, context ) );
 
@@ -707,7 +706,7 @@ void TestQgsProcessing::features()
   QCOMPARE( source->featureCount(), 5L );
 
   // test with selected features
-  context.setFlags( QgsProcessingContext::UseSelectionIfPresent );
+  params.insert( QStringLiteral( "layer" ), QVariant::fromValue( QgsProcessingFeatureSourceDefinition( layer->id(), true ) ) );
   layer->selectByIds( QgsFeatureIds() << 2 << 4 );
   source.reset( QgsProcessingParameters::parameterAsSource( def, params, context ) );
   ids = getIds( source->getFeatures() );
@@ -715,7 +714,7 @@ void TestQgsProcessing::features()
   QCOMPARE( source->featureCount(), 2L );
 
   // selection, but not using selected features
-  context.setFlags( QgsProcessingContext::Flags( 0 ) );
+  params.insert( QStringLiteral( "layer" ), QVariant::fromValue( QgsProcessingFeatureSourceDefinition( layer->id(), false ) ) );
   layer->selectByIds( QgsFeatureIds() << 2 << 4 );
   source.reset( QgsProcessingParameters::parameterAsSource( def, params, context ) );
   ids = getIds( source->getFeatures() );
@@ -723,16 +722,16 @@ void TestQgsProcessing::features()
   QCOMPARE( source->featureCount(), 5L );
 
   // using selected features, but no selection
-  context.setFlags( QgsProcessingContext::UseSelectionIfPresent );
+  params.insert( QStringLiteral( "layer" ), QVariant::fromValue( QgsProcessingFeatureSourceDefinition( layer->id(), true ) ) );
   layer->removeSelection();
   source.reset( QgsProcessingParameters::parameterAsSource( def, params, context ) );
   ids = getIds( source->getFeatures() );
-  QCOMPARE( ids, QgsFeatureIds() << 1 << 2 << 3 << 4 << 5 );
-  QCOMPARE( source->featureCount(), 5L );
+  QVERIFY( ids.isEmpty() );
+  QCOMPARE( source->featureCount(), 0L );
 
 
   // test that feature request is honored
-  context.setFlags( QgsProcessingContext::Flags( 0 ) );
+  params.insert( QStringLiteral( "layer" ), QVariant::fromValue( QgsProcessingFeatureSourceDefinition( layer->id(), false ) ) );
   source.reset( QgsProcessingParameters::parameterAsSource( def, params, context ) );
   ids = getIds( source->getFeatures( QgsFeatureRequest().setFilterFids( QgsFeatureIds() << 1 << 3 << 5 ) ) );
   QCOMPARE( ids, QgsFeatureIds() << 1 << 3 << 5 );
@@ -741,7 +740,7 @@ void TestQgsProcessing::features()
   QCOMPARE( source->featureCount(), 5L );
 
   //test that feature request is honored when using selections
-  context.setFlags( QgsProcessingContext::UseSelectionIfPresent );
+  params.insert( QStringLiteral( "layer" ), QVariant::fromValue( QgsProcessingFeatureSourceDefinition( layer->id(), true ) ) );
   layer->selectByIds( QgsFeatureIds() << 2 << 4 );
   source.reset( QgsProcessingParameters::parameterAsSource( def, params, context ) );
   ids = getIds( source->getFeatures( QgsFeatureRequest().setFlags( QgsFeatureRequest::NoGeometry ) ) );
@@ -754,7 +753,6 @@ void TestQgsProcessing::features()
     encountered = true;
   };
 
-  context.setFlags( QgsProcessingContext::Flags( 0 ) );
   context.setInvalidGeometryCheck( QgsFeatureRequest::GeometryAbortOnInvalid );
   context.setInvalidGeometryCallback( callback );
   QgsVectorLayer *polyLayer = new QgsVectorLayer( "Polygon", "v2", "memory" );
@@ -762,7 +760,7 @@ void TestQgsProcessing::features()
   f.setGeometry( QgsGeometry::fromWkt( QStringLiteral( "Polygon((0 0, 1 0, 0 1, 1 1, 0 0))" ) ) );
   polyLayer->dataProvider()->addFeatures( QgsFeatureList() << f );
   p.addMapLayer( polyLayer );
-  params.insert( QStringLiteral( "string" ), polyLayer->id() );
+  params.insert( QStringLiteral( "layer" ), polyLayer->id() );
 
   source.reset( QgsProcessingParameters::parameterAsSource( def, params, context ) );
   ids = getIds( source->getFeatures() );
@@ -793,9 +791,9 @@ void TestQgsProcessing::uniqueValues()
   p.addMapLayer( layer );
   context.setProject( &p );
 
-  QgsProcessingParameterDefinition *def = new QgsProcessingParameterString( QStringLiteral( "string" ) );
+  QgsProcessingParameterDefinition *def = new QgsProcessingParameterString( QStringLiteral( "layer" ) );
   QVariantMap params;
-  params.insert( QStringLiteral( "string" ), layer->id() );
+  params.insert( QStringLiteral( "layer" ), layer->id() );
 
   std::unique_ptr< QgsFeatureSource > source( QgsProcessingParameters::parameterAsSource( def, params, context ) );
 
@@ -831,7 +829,7 @@ void TestQgsProcessing::uniqueValues()
   QVERIFY( vals.contains( QString( "C" ) ) );
 
   // selection and using selection
-  context.setFlags( QgsProcessingContext::UseSelectionIfPresent );
+  params.insert( QStringLiteral( "layer" ), QVariant::fromValue( QgsProcessingFeatureSourceDefinition( layer->id(), true ) ) );
   source.reset( QgsProcessingParameters::parameterAsSource( def, params, context ) );
   QVERIFY( source->uniqueValues( -1 ).isEmpty() );
   QVERIFY( source->uniqueValues( 10001 ).isEmpty() );
@@ -860,23 +858,31 @@ void TestQgsProcessing::createIndex()
   p.addMapLayer( layer );
   context.setProject( &p );
 
-  QgsProcessingParameterDefinition *def = new QgsProcessingParameterString( QStringLiteral( "string" ) );
+  QgsProcessingParameterDefinition *def = new QgsProcessingParameterString( QStringLiteral( "layer" ) );
   QVariantMap params;
-  params.insert( QStringLiteral( "string" ), layer->id() );
+  params.insert( QStringLiteral( "layer" ), layer->id() );
 
   // disable selected features check
-  context.setFlags( QgsProcessingContext::Flags( 0 ) );
   std::unique_ptr< QgsFeatureSource > source( QgsProcessingParameters::parameterAsSource( def, params, context ) );
+  QVERIFY( source.get() );
   QgsSpatialIndex index( *source.get() );
   QList<QgsFeatureId> ids = index.nearestNeighbor( QgsPointXY( 2.1, 2 ), 1 );
   QCOMPARE( ids, QList<QgsFeatureId>() << 2 );
 
   // selected features check, but none selected
-  context.setFlags( QgsProcessingContext::UseSelectionIfPresent );
+  params.insert( QStringLiteral( "layer" ), QVariant::fromValue( QgsProcessingFeatureSourceDefinition( layer->id(), true ) ) );
   source.reset( QgsProcessingParameters::parameterAsSource( def, params, context ) );
-  index = QgsSpatialIndex( *source.get() );
-  ids = index.nearestNeighbor( QgsPointXY( 2.1, 2 ), 1 );
-  QCOMPARE( ids, QList<QgsFeatureId>() << 2 );
+  bool caught;
+  try
+  {
+    index = QgsSpatialIndex( *source.get() );
+    ids = index.nearestNeighbor( QgsPointXY( 2.1, 2 ), 1 );
+  }
+  catch ( ... )
+  {
+    caught = true;
+  }
+  QVERIFY( caught );
 
   // create selection
   layer->selectByIds( QgsFeatureIds() << 4 << 5 );
@@ -886,7 +892,7 @@ void TestQgsProcessing::createIndex()
   QCOMPARE( ids, QList<QgsFeatureId>() << 4 );
 
   // selection but not using selection mode
-  context.setFlags( QgsProcessingContext::Flags( 0 ) );
+  params.insert( QStringLiteral( "layer" ), QVariant::fromValue( QgsProcessingFeatureSourceDefinition( layer->id(), false ) ) );
   source.reset( QgsProcessingParameters::parameterAsSource( def, params, context ) );
   index = QgsSpatialIndex( *source.get() );
   ids = index.nearestNeighbor( QgsPointXY( 2.1, 2 ), 1 );
@@ -2305,6 +2311,22 @@ void TestQgsProcessing::combineLayerExtent()
   QGSCOMPARENEAR( ext.yMaximum(), 3536664, 10 );
 }
 
+void TestQgsProcessing::processingFeatureSource()
+{
+  QVariant source( QStringLiteral( "test.shp" ) );
+  QgsProcessingFeatureSourceDefinition fs( source, true );
+  QCOMPARE( fs.source, source );
+  QVERIFY( fs.selectedFeaturesOnly );
+
+  // test storing QgsProcessingFeatureSource in variant and retrieving
+  QVariant fsInVariant = QVariant::fromValue( fs );
+  QVERIFY( fsInVariant.isValid() );
+
+  QgsProcessingFeatureSourceDefinition fromVar = qvariant_cast<QgsProcessingFeatureSourceDefinition>( fsInVariant );
+  QCOMPARE( fromVar.source, source );
+  QVERIFY( fromVar.selectedFeaturesOnly );
+}
+
 void TestQgsProcessing::processingFeatureSink()
 {
   QVariant sink( QStringLiteral( "test.shp" ) );