[processing] recover previous value of formula in modeler calculator

#fixes 11539

Author: volaya

python/plugins/processing/algs/qgis/FieldsMapper.py

@@ -62,8 +62,8 @@ def defineCharacteristics(self):
     def getCustomParametersDialog(self):
         return FieldsMapperParametersDialog(self)
 
-    def getCustomModelerParametersDialog(self, modelAlg, algIndex=None):
-        return FieldsMapperModelerParametersDialog(self, modelAlg, algIndex)
+    def getCustomModelerParametersDialog(self, modelAlg, algName=None):
+        return FieldsMapperModelerParametersDialog(self, modelAlg, algName)
 
     def processAlgorithm(self, progress):
         layer = self.getParameterValue(self.INPUT_LAYER)

python/plugins/processing/core/GeoAlgorithm.py

@@ -161,7 +161,7 @@ def getCustomParametersDialog(self):
         """
         return None
 
-    def getCustomModelerParametersDialog(self, modelAlg, algIndex=None):
+    def getCustomModelerParametersDialog(self, modelAlg, algName=None):
         """If the algorithm has a custom parameters dialog when called
         from the modeler, it should be returned here, ready to be
         executed.

python/plugins/processing/modeler/CalculatorModelerAlgorithm.py

@@ -71,8 +71,8 @@ def processAlgorithm(self, progress):
             raise GeoAlgorithmExecutionException(
                 self.tr('Wrong formula: %s', 'CalculatorModelerAlgorithm') % formula)
 
-    def getCustomModelerParametersDialog(self, modelAlg, algIndex=None):
-        return CalculatorModelerParametersDialog(self, modelAlg, algIndex)
+    def getCustomModelerParametersDialog(self, modelAlg, algName=None):
+        return CalculatorModelerParametersDialog(self, modelAlg, algName)
 
 
 class CalculatorModelerParametersDialog(ModelerParametersDialog):
@@ -101,6 +101,8 @@ def setupUi(self):
         self.formulaText = QLineEdit()
         if hasattr(self.formulaText, 'setPlaceholderText'):
             self.formulaText.setPlaceholderText(self.tr('[Enter your formula here]', 'CalculatorModelerParametersDialog'))
+        alg = self.model.algs[self._algName]
+        self.formulaText.setText(alg.params[FORMULA])
         self.setWindowTitle(self.tr('Calculator', 'CalculatorModelerParametersDialog'))
         self.verticalLayout = QVBoxLayout()
         self.verticalLayout.setSpacing(2)