[processing] enable temporary outputs in QGIS Field Calculator (fix #9401)

Author: alexbruy

python/plugins/processing/algs/FieldsCalculator.py

@@ -37,7 +37,7 @@
 from processing.parameters.ParameterBoolean import ParameterBoolean
 from processing.parameters.ParameterSelection import ParameterSelection
 from processing.outputs.OutputVector import OutputVector
-from processing.tools import dataobjects, vector
+from processing.tools import dataobjects, vector, system
 
 from processing.algs.ui.FieldsCalculatorDialog import FieldsCalculatorDialog
 
@@ -85,6 +85,10 @@ def processAlgorithm(self, progress):
 
         output = self.getOutputFromName(self.OUTPUT_LAYER)
 
+        if output.value == '':
+            ext = output.getDefaultFileExtension(self)
+            output.value = system.getTempFilenameInTempFolder(output.name + '.' + ext)
+
         provider = layer.dataProvider()
         fields = layer.pendingFields()
         if newField:
@@ -143,7 +147,6 @@ def processAlgorithm(self, progress):
                 'An error occured while evaluating the calculation '
                 'string:\n' + error)
 
-
     def checkParameterValuesBeforeExecuting(self):
         newField = self.getParameterValue(self.NEW_FIELD)
         fieldName = self.getParameterValue(self.FIELD_NAME)
@@ -156,6 +159,5 @@ def checkParameterValuesBeforeExecuting(self):
             raise GeoAlgorithmExecutionException('Output is not set. '
                 'Please specify valid filename')
 
-
     def getCustomParametersDialog(self):
         return FieldsCalculatorDialog(self)

python/plugins/processing/algs/ui/FieldsCalculatorDialog.py

@@ -71,6 +71,10 @@ def __init__(self, alg):
         self.manageGui()
 
     def manageGui(self):
+        if hasattr(self.leOutputFile, 'setPlaceholderText'):
+            self.leOutputFile.setPlaceholderText(
+                self.tr('[Save to temporary file]'))
+
         self.mOutputFieldTypeComboBox.blockSignals(True)
         for t in self.alg.TYPE_NAMES:
             self.mOutputFieldTypeComboBox.addItem(t)