[processing] When converting models to python, correctly use a

nyalldawson · nyalldawson · commit fc8fd1e26b1b · 2019-02-13T19:17:30.000+10:00
multi-step feedback object to give scripts accurate progress reports

And also add in checks for cancelation between child algorithm
execution to allow generated scripts to early exit
diff --git a/src/core/processing/models/qgsprocessingmodelalgorithm.cpp b/src/core/processing/models/qgsprocessingmodelalgorithm.cpp
@@ -373,12 +373,21 @@ QStringList QgsProcessingModelAlgorithm::asPythonCode( const QgsProcessing::Pyth
 
   const QString algorithmClassName = safeName( name() );
 
+  QSet< QString > toExecute;
+  for ( auto childIt = mChildAlgorithms.constBegin(); childIt != mChildAlgorithms.constEnd(); ++childIt )
+  {
+    if ( childIt->isActive() && childIt->algorithm() )
+      toExecute.insert( childIt->childId() );
+  }
+  const int totalSteps = toExecute.count();
+
   switch ( outputType )
   {
     case QgsProcessing::PythonQgsProcessingAlgorithmSubclass:
     {
       lines << QStringLiteral( "from qgis.core import QgsProcessing" );
       lines << QStringLiteral( "from qgis.core import QgsProcessingAlgorithm" );
+      lines << QStringLiteral( "from qgis.core import QgsProcessingMultiStepFeedback" );
       // add specific parameter type imports
       const auto params = parameterDefinitions();
       QStringList importLines; // not a set - we need regular ordering
@@ -405,8 +414,12 @@ QStringList QgsProcessingModelAlgorithm::asPythonCode( const QgsProcessing::Pyth
       }
 
       lines << QString();
-      lines << indent + QStringLiteral( "def processAlgorithm(self, parameters, context, feedback):" );
+      lines << indent + QStringLiteral( "def processAlgorithm(self, parameters, context, model_feedback):" );
       currentIndent = indent + indent;
+
+      lines << currentIndent + QStringLiteral( "# Use a multi-step feedback, so that individual child algorithm progress reports are adjusted for the" );
+      lines << currentIndent + QStringLiteral( "# overall progress through the model" );
+      lines << currentIndent + QStringLiteral( "feedback = QgsProcessingMultiStepFeedback(%1, model_feedback)" ).arg( totalSteps );
       break;
     }
 #if 0
@@ -450,15 +463,9 @@ QStringList QgsProcessingModelAlgorithm::asPythonCode( const QgsProcessing::Pyth
   lines << currentIndent + QStringLiteral( "results = {}" );
   lines << currentIndent + QStringLiteral( "outputs = {}" );
 
-  QSet< QString > toExecute;
-  for ( auto childIt = mChildAlgorithms.constBegin(); childIt != mChildAlgorithms.constEnd(); ++childIt )
-  {
-    if ( childIt->isActive() && childIt->algorithm() )
-      toExecute.insert( childIt->childId() );
-  }
-
   QSet< QString > executed;
   bool executedAlg = true;
+  int currentStep = 0;
   while ( executedAlg && executed.count() < toExecute.count() )
   {
     executedAlg = false;
@@ -530,7 +537,15 @@ QStringList QgsProcessingModelAlgorithm::asPythonCode( const QgsProcessing::Pyth
       }
 
       lines << child.asPythonCode( outputType, childParams, currentIndent.size(), indentSize );
-
+      currentStep++;
+      if ( currentStep < totalSteps )
+      {
+        lines << QString();
+        lines << currentIndent + QStringLiteral( "feedback.setCurrentStep(%1)" ).arg( currentStep );
+        lines << currentIndent + QStringLiteral( "if feedback.isCanceled():" );
+        lines << currentIndent + indent + QStringLiteral( "return {}" );
+        lines << QString();
+      }
       executed.insert( childId );
     }
   }
diff --git a/tests/src/analysis/testqgsprocessing.cpp b/tests/src/analysis/testqgsprocessing.cpp
@@ -6986,6 +6986,7 @@ void TestQgsProcessing::modelExecution()
   QgsDebugMsg( actualParts.join( '\n' ) );
   QStringList expectedParts = QStringLiteral( "from qgis.core import QgsProcessing\n"
                               "from qgis.core import QgsProcessingAlgorithm\n"
+                              "from qgis.core import QgsProcessingMultiStepFeedback\n"
                               "from qgis.core import QgsProcessingParameterFeatureSource\n"
                               "from qgis.core import QgsProcessingParameterNumber\n"
                               "from qgis.core import QgsProcessingParameterFeatureSink\n"
@@ -7000,7 +7001,10 @@ void TestQgsProcessing::modelExecution()
                               "    self.addParameter(QgsProcessingParameterFeatureSink('cx1:MODEL_OUT_LAYER', '', type=QgsProcessing.TypeVectorPolygon, createByDefault=True, defaultValue=None))\n"
                               "    self.addParameter(QgsProcessingParameterFeatureSink('cx3:MY_OUT', '', type=QgsProcessing.TypeVectorAnyGeometry, createByDefault=True, defaultValue=None))\n"
                               "\n"
-                              "  def processAlgorithm(self, parameters, context, feedback):\n"
+                              "  def processAlgorithm(self, parameters, context, model_feedback):\n"
+                              "    # Use a multi-step feedback, so that individual child algorithm progress reports are adjusted for the\n"
+                              "    # overall progress through the model\n"
+                              "    feedback = QgsProcessingMultiStepFeedback(3, model_feedback)\n"
                               "    results = {}\n"
                               "    outputs = {}\n"
                               "    alg_params = {\n"
@@ -7014,11 +7018,21 @@ void TestQgsProcessing::modelExecution()
                               "    }\n"
                               "    outputs['cx1'] = processing.run('native:buffer', alg_params, context=context, feedback=feedback, is_child_algorithm=True)\n"
                               "    results['cx1:MODEL_OUT_LAYER'] = outputs['cx1']['OUTPUT']\n"
+                              "\n"
+                              "    feedback.setCurrentStep(1)\n"
+                              "    if feedback.isCanceled():\n"
+                              "      return {}\n"
+                              "\n"
                               "    alg_params = {\n"
                               "      'INPUT': outputs['cx1']['OUTPUT'],\n"
                               "      'OUTPUT': QgsProcessing.TEMPORARY_OUTPUT\n"
                               "    }\n"
                               "    outputs['cx2'] = processing.run('native:centroids', alg_params, context=context, feedback=feedback, is_child_algorithm=True)\n"
+                              "\n"
+                              "    feedback.setCurrentStep(2)\n"
+                              "    if feedback.isCanceled():\n"
+                              "      return {}\n"
+                              "\n"
                               "    alg_params = {\n"
                               "      'EXPRESSION': 'true',\n"
                               "      'INPUT': outputs['cx1']['OUTPUT'],\n"
