Add method to generate temporary destination parameter value

Author: nyalldawson

python/core/processing/qgsprocessingparameters.sip

@@ -1361,6 +1361,14 @@ class QgsProcessingParameterFeatureSink : QgsProcessingParameterDefinition
     virtual bool fromVariantMap( const QVariantMap &map );
 
 
+    virtual QString generateTemporaryDestination() const;
+%Docstring
+ Generates a temporary destination value for this parameter. The returned
+ value will be a file path or QGIS data provider URI suitable for
+ temporary storage of created layers and files.
+ :rtype: str
+%End
+
 };
 
 
@@ -1414,6 +1422,8 @@ class QgsProcessingParameterVectorOutput : QgsProcessingParameterDefinition
 
     virtual bool fromVariantMap( const QVariantMap &map );
 
+    virtual QString generateTemporaryDestination() const;
+
 
 };
 

src/core/processing/qgsprocessingparameters.cpp

@@ -2114,6 +2114,14 @@ bool QgsProcessingParameterFeatureSink::fromVariantMap( const QVariantMap &map )
   return true;
 }
 
+QString QgsProcessingParameterFeatureSink::generateTemporaryDestination() const
+{
+  if ( supportsNonFileBasedOutputs() )
+    return QStringLiteral( "memory:" );
+  else
+    return QgsProcessingDestinationParameter::generateTemporaryDestination();
+}
+
 QgsProcessingParameterRasterOutput::QgsProcessingParameterRasterOutput( const QString &name, const QString &description, const QVariant &defaultValue, bool optional )
   : QgsProcessingDestinationParameter( name, description, defaultValue, optional )
 {}
@@ -2331,6 +2339,11 @@ bool QgsProcessingDestinationParameter::fromVariantMap( const QVariantMap &map )
   return true;
 }
 
+QString QgsProcessingDestinationParameter::generateTemporaryDestination() const
+{
+  return QgsProcessingUtils::generateTempFilename( name() + '.' + defaultFileExtension() );
+}
+
 QgsProcessingParameterVectorOutput::QgsProcessingParameterVectorOutput( const QString &name, const QString &description, QgsProcessingParameterDefinition::LayerType type, const QVariant &defaultValue, bool optional )
   : QgsProcessingParameterDefinition( name, description, defaultValue, optional )
   , mDataType( type )

src/core/processing/qgsprocessingparameters.h

@@ -1313,6 +1313,13 @@ class CORE_EXPORT QgsProcessingDestinationParameter : public QgsProcessingParame
      */
     virtual QString defaultFileExtension() const = 0;
 
+    /**
+     * Generates a temporary destination value for this parameter. The returned
+     * value will be a file path or QGIS data provider URI suitable for
+     * temporary storage of created layers and files.
+     */
+    virtual QString generateTemporaryDestination() const;
+
   private:
 
     bool mSupportsNonFileBasedOutputs = true;
@@ -1364,6 +1371,7 @@ class CORE_EXPORT QgsProcessingParameterFeatureSink : public QgsProcessingDestin
 
     QVariantMap toVariantMap() const override;
     bool fromVariantMap( const QVariantMap &map ) override;
+    QString generateTemporaryDestination() const override;
 
   private:
 

tests/src/core/testqgsprocessing.cpp

@@ -2812,6 +2812,10 @@ void TestQgsProcessing::parameterFeatureSink()
   QCOMPARE( def->valueAsPythonString( QVariant::fromValue( QgsProperty::fromExpression( "\"a\"=1" ) ), context ), QStringLiteral( "QgsProperty.fromExpression('\"a\"=1')" ) );
 
   QCOMPARE( def->defaultFileExtension(), QStringLiteral( "shp" ) );
+  QCOMPARE( def->generateTemporaryDestination(), QStringLiteral( "memory:" ) );
+  def->setSupportsNonFileBasedOutputs( false );
+  QVERIFY( def->generateTemporaryDestination().endsWith( QStringLiteral( ".shp" ) ) );
+  QVERIFY( def->generateTemporaryDestination().startsWith( QgsProcessingUtils::tempFolder() ) );
 
   QVariantMap map = def->toVariantMap();
   QgsProcessingParameterFeatureSink fromMap( "x" );
@@ -2933,6 +2937,8 @@ void TestQgsProcessing::parameterRasterOut()
   QVERIFY( def->checkValueIsAcceptable( "c:/Users/admin/Desktop/roads_clipped_transformed_v1_reprojected_final_clipped_aAAA.tif", &context ) );
 
   QCOMPARE( def->defaultFileExtension(), QStringLiteral( "tif" ) );
+  QVERIFY( def->generateTemporaryDestination().endsWith( QStringLiteral( ".tif" ) ) );
+  QVERIFY( def->generateTemporaryDestination().startsWith( QgsProcessingUtils::tempFolder() ) );
 
   QVariantMap params;
   params.insert( "non_optional", "test.tif" );
@@ -2985,6 +2991,8 @@ void TestQgsProcessing::parameterFileOut()
   std::unique_ptr< QgsProcessingParameterFileOutput > def( new QgsProcessingParameterFileOutput( "non_optional", QString(), QStringLiteral( "BMP files (*.bmp)" ), QString(), false ) );
   QCOMPARE( def->fileFilter(), QStringLiteral( "BMP files (*.bmp)" ) );
   QCOMPARE( def->defaultFileExtension(), QStringLiteral( "bmp" ) );
+  QVERIFY( def->generateTemporaryDestination().endsWith( QStringLiteral( ".bmp" ) ) );
+  QVERIFY( def->generateTemporaryDestination().startsWith( QgsProcessingUtils::tempFolder() ) );
   def->setFileFilter( QStringLiteral( "PCX files (*.pcx)" ) );
   QCOMPARE( def->fileFilter(), QStringLiteral( "PCX files (*.pcx)" ) );
   QCOMPARE( def->defaultFileExtension(), QStringLiteral( "pcx" ) );
@@ -2994,6 +3002,8 @@ void TestQgsProcessing::parameterFileOut()
   QCOMPARE( def->defaultFileExtension(), QStringLiteral( "pcx" ) );
   def->setFileFilter( QString() );
   QCOMPARE( def->defaultFileExtension(), QStringLiteral( "file" ) );
+  QVERIFY( def->generateTemporaryDestination().endsWith( QStringLiteral( ".file" ) ) );
+  QVERIFY( def->generateTemporaryDestination().startsWith( QgsProcessingUtils::tempFolder() ) );
 
   QVERIFY( !def->checkValueIsAcceptable( false ) );
   QVERIFY( !def->checkValueIsAcceptable( true ) );