Catch exception from script and pipe it into feedback

Author: elpaso

src/core/processing/qgsprocessingalgrunnertask.cpp

@@ -27,20 +27,30 @@ QgsProcessingAlgRunnerTask::QgsProcessingAlgRunnerTask( const QgsProcessingAlgor
   , mParameters( parameters )
   , mContext( context )
   , mFeedback( feedback )
-  , mAlgorithm( algorithm->create() )
 {
   if ( !mFeedback )
   {
     mOwnedFeedback.reset( new QgsProcessingFeedback() );
     mFeedback = mOwnedFeedback.get();
   }
-  if ( !( mAlgorithm && mAlgorithm->prepare( mParameters, context, mFeedback ) ) )
+  try
+  {
+    mAlgorithm.reset( algorithm->create() );
+    if ( !( mAlgorithm && mAlgorithm->prepare( mParameters, context, mFeedback ) ) )
+      cancel();
+  }
+  catch ( QgsProcessingException &e )
+  {
+    QgsMessageLog::logMessage( e.what(), QObject::tr( "Processing" ), Qgis::Critical );
+    mFeedback->reportError( e.what() );
     cancel();
+  }
 }
 
 void QgsProcessingAlgRunnerTask::cancel()
 {
-  mFeedback->cancel();
+  if ( mFeedback )
+    mFeedback->cancel();
   QgsTask::cancel();
 }
 

tests/src/python/test_qgsprocessingalgrunner.py

@@ -28,11 +28,21 @@
     QgsProcessingAlgRunnerTask,
     QgsProcessingAlgorithm,
     QgsProject,
+    QgsProcessingFeedback,
 )
 
 start_app()
 
 
+class ConsoleFeedBack(QgsProcessingFeedback):
+
+    _error = ''
+
+    def reportError(self, error, fatalError=False):
+        self._error = error
+        print(error)
+
+
 class CrashingProcessingAlgorithm(QgsProcessingAlgorithm):
     """
     Wrong class in factory createInstance()
@@ -89,10 +99,11 @@ def test_bad_script_dont_crash(self):  # spellok
 
         context = QgsProcessingContext()
         context.setProject(QgsProject.instance())
-        with self.assertRaises(Exception) as e:
-            QgsProcessingAlgRunnerTask(CrashingProcessingAlgorithm(), {}, context=context)
+        feedback = ConsoleFeedBack()
 
-        self.assertEqual(str(e.exception), 'unknown')
+        task = QgsProcessingAlgRunnerTask(CrashingProcessingAlgorithm(), {}, context=context, feedback=feedback)
+        self.assertTrue(task.isCanceled())
+        self.assertEqual(feedback._error, 'Error creating algorithm from createInstance()')
 
 
 if __name__ == '__main__':