Add method to evaluate parameters to compatible vector layers

of a specified type

python/core/processing/qgsprocessingparameters.sip

@@ -472,6 +472,22 @@ class QgsProcessingParameters
  :rtype: QgsProcessingFeatureSource
 %End
 
+    static QString parameterAsCompatibleSourceLayerPath( const QgsProcessingParameterDefinition *definition, const QVariantMap &parameters,
+        QgsProcessingContext &context, const QStringList &compatibleFormats, const QString &preferredFormat = QString( "shp" ), QgsProcessingFeedback *feedback = 0 );
+%Docstring
+ Evaluates the parameter with matching ``definition`` to a source vector layer file path of compatible format.
+
+ If the parameter is evaluated to an existing layer, and that layer is not of the format listed in the
+ ``compatibleFormats`` argument, then the layer will first be exported to a compatible format
+ in a temporary location. The function will then return the path to that temporary file.
+
+ ``compatibleFormats`` should consist entirely of lowercase file extensions, e.g. 'shp'.
+
+ The ``preferredFormat`` argument is used to specify to desired file extension to use when a temporary
+ layer export is required. This defaults to shapefiles, because shapefiles are the future (don't believe the geopackage hype!).
+ :rtype: str
+%End
+
     static QgsMapLayer *parameterAsLayer( const QgsProcessingParameterDefinition *definition, const QVariantMap &parameters, QgsProcessingContext &context );
 %Docstring
  Evaluates the parameter with matching ``definition`` to a map layer.

python/core/processing/qgsprocessingutils.sip

@@ -158,6 +158,27 @@ class QgsProcessingUtils
  :rtype: str
 %End
 
+    static QString convertToCompatibleFormat( const QgsVectorLayer *layer,
+        bool selectedFeaturesOnly,
+        const QString &baseName,
+        const QStringList &compatibleFormats,
+        const QString &preferredFormat,
+        QgsProcessingContext &context,
+        QgsProcessingFeedback *feedback );
+%Docstring
+ Converts a source vector ``layer`` to a file path to a vector layer of compatible format.
+
+ If the specified ``layer`` is not of the format listed in the
+ ``compatibleFormats`` argument, then the layer will first be exported to a compatible format
+ in a temporary location using ``baseName``. The function will then return the path to that temporary file.
+
+ ``compatibleFormats`` should consist entirely of lowercase file extensions, e.g. 'shp'.
+
+ The ``preferredFormat`` argument is used to specify to desired file extension to use when a temporary
+ layer export is required. This defaults to shapefiles.
+ :rtype: str
+%End
+
 };
 
 class QgsProcessingFeatureSource : QgsFeatureSource

src/core/processing/qgsprocessingparameters.cpp

@@ -21,6 +21,7 @@
 #include "qgsvectorlayerfeatureiterator.h"
 #include "qgsprocessingoutputs.h"
 #include "qgssettings.h"
+#include "qgsvectorfilewriter.h"
 
 bool QgsProcessingParameters::isDynamic( const QVariantMap &parameters, const QString &name )
 {
@@ -327,6 +328,49 @@ QgsProcessingFeatureSource *QgsProcessingParameters::parameterAsSource( const Qg
   }
 }
 
+QString QgsProcessingParameters::parameterAsCompatibleSourceLayerPath( const QgsProcessingParameterDefinition *definition, const QVariantMap &parameters, QgsProcessingContext &context, const QStringList &compatibleFormats, const QString &preferredFormat, QgsProcessingFeedback *feedback )
+{
+  if ( !definition )
+    return QString();
+
+  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 QString();
+
+  QgsVectorLayer *vl = qobject_cast< QgsVectorLayer *>( QgsProcessingUtils::mapLayerFromString( layerRef, context ) );
+  if ( !vl )
+    return QString();
+
+  return QgsProcessingUtils::convertToCompatibleFormat( vl, selectedFeaturesOnly, definition->name(),
+         compatibleFormats, preferredFormat, context, feedback );
+}
+
+
 QgsMapLayer *QgsProcessingParameters::parameterAsLayer( const QgsProcessingParameterDefinition *definition, const QVariantMap &parameters, QgsProcessingContext &context )
 {
   if ( !definition )

src/core/processing/qgsprocessingparameters.h

@@ -32,6 +32,7 @@ class QgsFeatureSink;
 class QgsFeatureSource;
 class QgsProcessingFeatureSource;
 class QgsProcessingOutputDefinition;
+class QgsProcessingFeedback;
 
 /**
  * \class QgsProcessingFeatureSourceDefinition
@@ -508,6 +509,21 @@ class CORE_EXPORT QgsProcessingParameters
      */
     static QgsProcessingFeatureSource *parameterAsSource( const QgsProcessingParameterDefinition *definition, const QVariantMap &parameters, QgsProcessingContext &context ) SIP_FACTORY;
 
+    /**
+     * Evaluates the parameter with matching \a definition to a source vector layer file path of compatible format.
+     *
+     * If the parameter is evaluated to an existing layer, and that layer is not of the format listed in the
+     * \a compatibleFormats argument, then the layer will first be exported to a compatible format
+     * in a temporary location. The function will then return the path to that temporary file.
+     *
+     * \a compatibleFormats should consist entirely of lowercase file extensions, e.g. 'shp'.
+     *
+     * The \a preferredFormat argument is used to specify to desired file extension to use when a temporary
+     * layer export is required. This defaults to shapefiles, because shapefiles are the future (don't believe the geopackage hype!).
+     */
+    static QString parameterAsCompatibleSourceLayerPath( const QgsProcessingParameterDefinition *definition, const QVariantMap &parameters,
+        QgsProcessingContext &context, const QStringList &compatibleFormats, const QString &preferredFormat = QString( "shp" ), QgsProcessingFeedback *feedback = nullptr );
+
     /**
      * Evaluates the parameter with matching \a definition to a map layer.
      *

src/core/processing/qgsprocessingutils.cpp

@@ -461,6 +461,42 @@ QString QgsProcessingUtils::formatHelpMapAsHtml( const QVariantMap &map, const Q
   return s;
 }
 
+QString QgsProcessingUtils::convertToCompatibleFormat( const QgsVectorLayer *vl, bool selectedFeaturesOnly, const QString &baseName, const QStringList &compatibleFormats, const QString &preferredFormat, QgsProcessingContext &context, QgsProcessingFeedback *feedback )
+{
+  bool requiresTranslation = selectedFeaturesOnly;
+  if ( !selectedFeaturesOnly )
+  {
+    QFileInfo fi( vl->source() );
+    requiresTranslation = !compatibleFormats.contains( fi.suffix(), Qt::CaseInsensitive );
+  }
+
+  if ( requiresTranslation )
+  {
+    QString temp = QgsProcessingUtils::generateTempFilename( baseName + '.' + preferredFormat );
+
+    QgsVectorFileWriter writer( temp, context.defaultEncoding(),
+                                vl->fields(), vl->wkbType(), vl->crs(), QgsVectorFileWriter::driverForExtension( preferredFormat ) );
+    QgsFeature f;
+    QgsFeatureIterator it;
+    if ( selectedFeaturesOnly )
+      it = vl->getSelectedFeatures();
+    else
+      it = vl->getFeatures();
+
+    while ( it.nextFeature( f ) )
+    {
+      if ( feedback->isCanceled() )
+        return QString();
+      writer.addFeature( f, QgsFeatureSink::FastInsert );
+    }
+    return temp;
+  }
+  else
+  {
+    return vl->source();
+  }
+}
+
 
 //
 // QgsProcessingFeatureSource

src/core/processing/qgsprocessingutils.h

@@ -28,6 +28,7 @@
 class QgsProject;
 class QgsProcessingContext;
 class QgsMapLayerStore;
+class QgsProcessingFeedback;
 
 #include <QString>
 #include <QVariant>
@@ -189,6 +190,26 @@ class CORE_EXPORT QgsProcessingUtils
      */
     static QString formatHelpMapAsHtml( const QVariantMap &map, const QgsProcessingAlgorithm *algorithm );
 
+    /**
+     * Converts a source vector \a layer to a file path to a vector layer of compatible format.
+     *
+     * If the specified \a layer is not of the format listed in the
+     * \a compatibleFormats argument, then the layer will first be exported to a compatible format
+     * in a temporary location using \a baseName. The function will then return the path to that temporary file.
+     *
+     * \a compatibleFormats should consist entirely of lowercase file extensions, e.g. 'shp'.
+     *
+     * The \a preferredFormat argument is used to specify to desired file extension to use when a temporary
+     * layer export is required. This defaults to shapefiles.
+     */
+    static QString convertToCompatibleFormat( const QgsVectorLayer *layer,
+        bool selectedFeaturesOnly,
+        const QString &baseName,
+        const QStringList &compatibleFormats,
+        const QString &preferredFormat,
+        QgsProcessingContext &context,
+        QgsProcessingFeedback *feedback );
+
   private:
 
     static bool canUseLayer( const QgsRasterLayer *layer );

tests/src/core/testqgsprocessing.cpp

@@ -333,6 +333,7 @@ class TestQgsProcessing: public QObject
     void modelExecution();
     void modelAcceptableValues();
     void tempUtils();
+    void convertCompatible();
 
   private:
 
@@ -5039,5 +5040,80 @@ void TestQgsProcessing::tempUtils()
   QVERIFY( tempFile2.startsWith( tempFolder ) );
 }
 
+void TestQgsProcessing::convertCompatible()
+{
+  // start with a compatible shapefile
+  QString testDataDir = QStringLiteral( TEST_DATA_DIR ) + '/'; //defined in CmakeLists.txt
+  QString vector = testDataDir + "points.shp";
+  QgsVectorLayer *layer = new QgsVectorLayer( vector, "vl" );
+  QgsProject p;
+  p.addMapLayer( layer );
+
+  QgsProcessingContext context;
+  context.setProject( &p );
+  QgsProcessingFeedback feedback;
+  QString out = QgsProcessingUtils::convertToCompatibleFormat( layer, false, QStringLiteral( "test" ), QStringList() << "shp", QString( "shp" ), context, &feedback );
+  // layer should be returned unchanged - underlying source is compatible
+  QCOMPARE( out, layer->source() );
+
+  // don't include shp as compatible type
+  out = QgsProcessingUtils::convertToCompatibleFormat( layer, false, QStringLiteral( "test" ), QStringList() << "tab", QString( "tab" ), context, &feedback );
+  QVERIFY( out != layer->source() );
+  QVERIFY( out.endsWith( ".tab" ) );
+  QVERIFY( out.startsWith( QgsProcessingUtils::tempFolder() ) );
+
+  // make sure all features are copied
+  QgsVectorLayer *t = new QgsVectorLayer( out, "vl2" );
+  QCOMPARE( layer->featureCount(), t->featureCount() );
+  QCOMPARE( layer->crs(), t->crs() );
+
+  // use a selection - this will require translation
+  QgsFeatureIds ids;
+  QgsFeature f;
+  QgsFeatureIterator it = layer->getFeatures();
+  it.nextFeature( f );
+  ids.insert( f.id() );
+  it.nextFeature( f );
+  ids.insert( f.id() );
+
+  layer->selectByIds( ids );
+  out = QgsProcessingUtils::convertToCompatibleFormat( layer, true, QStringLiteral( "test" ), QStringList() << "tab", QString( "tab" ), context, &feedback );
+  QVERIFY( out != layer->source() );
+  QVERIFY( out.endsWith( ".tab" ) );
+  QVERIFY( out.startsWith( QgsProcessingUtils::tempFolder() ) );
+  delete t;
+  t = new QgsVectorLayer( out, "vl2" );
+  QCOMPARE( t->featureCount(), static_cast< long >( ids.count() ) );
+
+  // using a selection but existing format - will still require translation
+  out = QgsProcessingUtils::convertToCompatibleFormat( layer, true, QStringLiteral( "test" ), QStringList() << "shp", QString( "shp" ), context, &feedback );
+  QVERIFY( out != layer->source() );
+  QVERIFY( out.endsWith( ".shp" ) );
+  QVERIFY( out.startsWith( QgsProcessingUtils::tempFolder() ) );
+  delete t;
+  t = new QgsVectorLayer( out, "vl2" );
+  QCOMPARE( t->featureCount(), static_cast< long >( ids.count() ) );
+
+
+  // also test evaluating parameter to compatible format
+  std::unique_ptr< QgsProcessingParameterDefinition > def( new QgsProcessingParameterFeatureSource( QStringLiteral( "source" ) ) );
+  QVariantMap params;
+  params.insert( QStringLiteral( "source" ), QgsProcessingFeatureSourceDefinition( layer->id(), false ) );
+  out = QgsProcessingParameters::parameterAsCompatibleSourceLayerPath( def.get(), params, context, QStringList() << "shp", QString( "shp" ), &feedback );
+  QCOMPARE( out, layer->source() );
+
+  out = QgsProcessingParameters::parameterAsCompatibleSourceLayerPath( def.get(), params, context, QStringList() << "tab", QString( "tab" ), &feedback );
+  QVERIFY( out != layer->source() );
+  QVERIFY( out.endsWith( ".tab" ) );
+  QVERIFY( out.startsWith( QgsProcessingUtils::tempFolder() ) );
+
+  // selected only, will force export
+  params.insert( QStringLiteral( "source" ), QgsProcessingFeatureSourceDefinition( layer->id(), true ) );
+  out = QgsProcessingParameters::parameterAsCompatibleSourceLayerPath( def.get(), params, context, QStringList() << "shp", QString( "shp" ), &feedback );
+  QVERIFY( out != layer->source() );
+  QVERIFY( out.endsWith( ".shp" ) );
+  QVERIFY( out.startsWith( QgsProcessingUtils::tempFolder() ) );
+}
+
 QGSTEST_MAIN( TestQgsProcessing )
 #include "testqgsprocessing.moc"