[processing] Add a model-only "load layer to project" algorithm

This can be used to force loading a layer into the current project. The primary use case here is to load a preset layer as part of a model, but it's also useful for loading results from the 'package layers' algorithm into the project.
qgis · Nov 26, 2017 · 3310343 · 3310343
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diff --git a/src/analysis/CMakeLists.txt b/src/analysis/CMakeLists.txt
@@ -41,6 +41,7 @@ SET(QGIS_ANALYSIS_SRCS
   processing/qgsalgorithmjoinbyattribute.cpp
   processing/qgsalgorithmjoinwithlines.cpp
   processing/qgsalgorithmlineintersection.cpp
+  processing/qgsalgorithmloadlayer.cpp
   processing/qgsalgorithmmeancoordinates.cpp
   processing/qgsalgorithmmergelines.cpp
   processing/qgsalgorithmminimumenclosingcircle.cpp

diff --git a/src/analysis/processing/qgsalgorithmloadlayer.cpp b/src/analysis/processing/qgsalgorithmloadlayer.cpp
@@ -0,0 +1,83 @@
+/***************************************************************************
+                         qgsalgorithmloadlayer.cpp
+                         ---------------------
+    begin                : November 2017
+    copyright            : (C) 2017 by Nyall Dawson
+    email                : nyall dot dawson at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgsalgorithmloadlayer.h"
+
+///@cond PRIVATE
+
+QString QgsLoadLayerAlgorithm::name() const
+{
+  return QStringLiteral( "loadlayer" );
+}
+
+QgsProcessingAlgorithm::Flags QgsLoadLayerAlgorithm::flags() const
+{
+  return FlagHideFromToolbox;
+}
+
+QString QgsLoadLayerAlgorithm::displayName() const
+{
+  return QObject::tr( "Load layer into project" );
+}
+
+QStringList QgsLoadLayerAlgorithm::tags() const
+{
+  return QObject::tr( "load,open,layer,raster,vector,project" ).split( ',' );
+}
+
+QString QgsLoadLayerAlgorithm::group() const
+{
+  return QObject::tr( "Modeler tool" );
+}
+
+QString QgsLoadLayerAlgorithm::shortHelpString() const
+{
+  return QObject::tr( "This algorithm loads a layer to the current project." );
+}
+
+QgsLoadLayerAlgorithm *QgsLoadLayerAlgorithm::createInstance() const
+{
+  return new QgsLoadLayerAlgorithm();
+}
+
+void QgsLoadLayerAlgorithm::initAlgorithm( const QVariantMap & )
+{
+  addParameter( new QgsProcessingParameterMapLayer( QStringLiteral( "INPUT" ), QObject::tr( "Layer" ) ) );
+  addParameter( new QgsProcessingParameterString( QStringLiteral( "NAME" ), QObject::tr( "Loaded layer name" ) ) );
+  addOutput( new QgsProcessingOutputMapLayer( QStringLiteral( "OUTPUT" ), QObject::tr( "Layer" ) ) );
+}
+
+QVariantMap QgsLoadLayerAlgorithm::processAlgorithm( const QVariantMap &parameters, QgsProcessingContext &context, QgsProcessingFeedback * )
+{
+  QgsMapLayer *layer = parameterAsLayer( parameters, QStringLiteral( "INPUT" ), context );
+  QString name = parameterAsString( parameters, QStringLiteral( "NAME" ), context );
+
+  if ( !layer )
+    throw QgsProcessingException( QObject::tr( "Invalid input layer" ) );
+
+  if ( name.isEmpty() )
+    throw QgsProcessingException( QObject::tr( "Invalid (empty) layer name" ) );
+
+  layer->setName( name );
+  context.addLayerToLoadOnCompletion( layer->id(), QgsProcessingContext::LayerDetails( name, context.project(), name ) );
+
+  QVariantMap results;
+  results.insert( QStringLiteral( "OUTPUT" ), layer->id() );
+  return results;
+}
+
+///@endcond
diff --git a/src/analysis/processing/qgsalgorithmloadlayer.h b/src/analysis/processing/qgsalgorithmloadlayer.h
@@ -0,0 +1,53 @@
+/***************************************************************************
+                         qgsalgorithmloadlayer.h
+                         ---------------------
+    begin                : November 2017
+    copyright            : (C) 2017 by Nyall Dawson
+    email                : nyall dot dawson at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSALGORITHMLOADLAYER_H
+#define QGSALGORITHMLOADLAYER_H
+
+#define SIP_NO_FILE
+
+#include "qgis.h"
+#include "qgsprocessingalgorithm.h"
+
+///@cond PRIVATE
+
+/**
+ * Native rename layer algorithm.
+ */
+class QgsLoadLayerAlgorithm : public QgsProcessingAlgorithm
+{
+  public:
+    QgsLoadLayerAlgorithm() = default;
+    void initAlgorithm( const QVariantMap &configuration = QVariantMap() ) override;
+    Flags flags() const override;
+    QString name() const override;
+    QString displayName() const override;
+    virtual QStringList tags() const override;
+    QString group() const override;
+    QString shortHelpString() const override;
+    QgsLoadLayerAlgorithm *createInstance() const override SIP_FACTORY;
+
+  protected:
+
+    virtual QVariantMap processAlgorithm( const QVariantMap &parameters,
+                                          QgsProcessingContext &context, QgsProcessingFeedback * ) override;
+
+};
+
+///@endcond PRIVATE
+
+#endif // QGSALGORITHMLOADLAYER_H
diff --git a/src/analysis/processing/qgsnativealgorithms.cpp b/src/analysis/processing/qgsnativealgorithms.cpp
@@ -38,6 +38,7 @@
 #include "qgsalgorithmjoinbyattribute.h"
 #include "qgsalgorithmjoinwithlines.h"
 #include "qgsalgorithmlineintersection.h"
+#include "qgsalgorithmloadlayer.h"
 #include "qgsalgorithmmeancoordinates.h"
 #include "qgsalgorithmmergelines.h"
 #include "qgsalgorithmminimumenclosingcircle.h"
@@ -116,6 +117,7 @@ void QgsNativeAlgorithms::loadAlgorithms()
   addAlgorithm( new QgsJoinByAttributeAlgorithm() );
   addAlgorithm( new QgsJoinWithLinesAlgorithm() );
   addAlgorithm( new QgsLineIntersectionAlgorithm() );
+  addAlgorithm( new QgsLoadLayerAlgorithm() );
   addAlgorithm( new QgsMeanCoordinatesAlgorithm() );
   addAlgorithm( new QgsMergeLinesAlgorithm() );
   addAlgorithm( new QgsMinimumEnclosingCircleAlgorithm() );

diff --git a/tests/src/analysis/testqgsprocessingalgs.cpp b/tests/src/analysis/testqgsprocessingalgs.cpp
@@ -35,9 +35,11 @@ class TestQgsProcessingAlgs: public QObject
     void cleanup() {} // will be called after every testfunction.
     void packageAlg();
     void renameLayerAlg();
+    void loadLayerAlg();
 
   private:
 
+    QString mPointLayerPath;
     QgsVectorLayer *mPointsLayer = nullptr;
     QgsVectorLayer *mPolygonLayer = nullptr;
 
@@ -59,7 +61,8 @@ void TestQgsProcessingAlgs::initTestCase()
 
   QString pointsFileName = dataDir + "/points.shp";
   QFileInfo pointFileInfo( pointsFileName );
-  mPointsLayer = new QgsVectorLayer( pointFileInfo.filePath(),
+  mPointLayerPath = pointFileInfo.filePath();
+  mPointsLayer = new QgsVectorLayer( mPointLayerPath,
                                      QStringLiteral( "points" ), QStringLiteral( "ogr" ) );
   QVERIFY( mPointsLayer->isValid() );
   // Register the layer with the registry
@@ -169,6 +172,51 @@ void TestQgsProcessingAlgs::renameLayerAlg()
   QCOMPARE( results.value( "OUTPUT" ).toString(), QStringLiteral( "new name2" ) );
 }
 
+void TestQgsProcessingAlgs::loadLayerAlg()
+{
+  const QgsProcessingAlgorithm *package( QgsApplication::processingRegistry()->algorithmById( QStringLiteral( "native:loadlayer" ) ) );
+  QVERIFY( package );
+
+  std::unique_ptr< QgsProcessingContext > context = qgis::make_unique< QgsProcessingContext >();
+  QgsProject p;
+  context->setProject( &p );
+
+  QgsProcessingFeedback feedback;
+
+  QVariantMap parameters;
+
+  // bad layer
+  parameters.insert( QStringLiteral( "INPUT" ), QStringLiteral( "bad layer" ) );
+  parameters.insert( QStringLiteral( "NAME" ), QStringLiteral( "new name" ) );
+  bool ok = false;
+  ( void )package->run( parameters, *context, &feedback, &ok );
+  QVERIFY( !ok );
+  QVERIFY( context->layersToLoadOnCompletion().empty() );
+
+  //invalid name
+  parameters.insert( QStringLiteral( "INPUT" ), mPointLayerPath );
+  parameters.insert( QStringLiteral( "NAME" ), QString() );
+  ok = false;
+  ( void )package->run( parameters, *context, &feedback, &ok );
+  QVERIFY( !ok );
+  QVERIFY( context->layersToLoadOnCompletion().empty() );
+
+  //good params
+  parameters.insert( QStringLiteral( "INPUT" ), mPointLayerPath );
+  parameters.insert( QStringLiteral( "NAME" ), QStringLiteral( "my layer" ) );
+  ok = false;
+  QVariantMap results = package->run( parameters, *context, &feedback, &ok );
+  QVERIFY( ok );
+  QVERIFY( !context->layersToLoadOnCompletion().empty() );
+  QString layerId = context->layersToLoadOnCompletion().keys().at( 0 );
+  QCOMPARE( results.value( QStringLiteral( "OUTPUT" ) ).toString(), layerId );
+  QVERIFY( !layerId.isEmpty() );
+  QVERIFY( context->temporaryLayerStore()->mapLayer( layerId ) );
+  QCOMPARE( context->layersToLoadOnCompletion().value( layerId, QgsProcessingContext::LayerDetails( QString(), nullptr, QString() ) ).name, QStringLiteral( "my layer" ) );
+  QCOMPARE( context->layersToLoadOnCompletion().value( layerId, QgsProcessingContext::LayerDetails( QString(), nullptr, QString() ) ).project, &p );
+  QCOMPARE( context->layersToLoadOnCompletion().value( layerId, QgsProcessingContext::LayerDetails( QString(), nullptr, QString() ) ).outputName, QStringLiteral( "my layer" ) );
+}
+
 
 QGSTEST_MAIN( TestQgsProcessingAlgs )
 #include "testqgsprocessingalgs.moc"