[processing] Fix crash when algorithms fail to prepare

nyalldawson · nyalldawson · commit cdf0cd19fb92 · 2018-02-26T10:57:47.000+11:00
Refs #15640 (cherry-picked from 2900ace)
diff --git a/python/plugins/processing/algs/qgis/FieldsMapper.py b/python/plugins/processing/algs/qgis/FieldsMapper.py
@@ -138,10 +138,11 @@ def prepareAlgorithm(self, parameters, context, feedback):
             expression.setDistanceUnits(context.project().distanceUnits())
             expression.setAreaUnits(context.project().areaUnits())
             if expression.hasParserError():
-                raise QgsProcessingException(
+                feedback.reportError(
                     self.tr(u'Parser error in expression "{}": {}')
                     .format(expression.expression(),
                             expression.parserErrorString()))
+                return False
             self.expressions.append(expression)
         return True
 
diff --git a/src/core/processing/qgsprocessingalgrunnertask.cpp b/src/core/processing/qgsprocessingalgrunnertask.cpp
@@ -41,10 +41,14 @@ QgsProcessingAlgRunnerTask::QgsProcessingAlgRunnerTask( const QgsProcessingAlgor
 void QgsProcessingAlgRunnerTask::cancel()
 {
   mFeedback->cancel();
+  QgsTask::cancel();
 }
 
 bool QgsProcessingAlgRunnerTask::run()
 {
+  if ( isCanceled() )
+    return false;
+
   connect( mFeedback, &QgsFeedback::progressChanged, this, &QgsProcessingAlgRunnerTask::setProgress );
   bool ok = false;
   try

Original file line number	Diff line number	Diff line change
`@@ -41,10 +41,14 @@ QgsProcessingAlgRunnerTask::QgsProcessingAlgRunnerTask( const QgsProcessingAlgor`
`41`	`41`	`void QgsProcessingAlgRunnerTask::cancel()`
`42`	`42`	`{`
`43`	`43`	`mFeedback->cancel();`
	`44`	`+ QgsTask::cancel();`
`44`	`45`	`}`
`45`	`46`
`46`	`47`	`bool QgsProcessingAlgRunnerTask::run()`
`47`	`48`	`{`
	`49`	`+ if ( isCanceled() )`
	`50`	`+ return false;`
	`51`	`+`
`48`	`52`	`connect( mFeedback, &QgsFeedback::progressChanged, this, &QgsProcessingAlgRunnerTask::setProgress );`
`49`	`53`	`bool ok = false;`
`50`	`54`	`try`