[processing] added check to ensure input layers are valid

python/plugins/processing/core/GeoAlgorithm.py

@@ -246,6 +246,21 @@ def execute(self, progress=None, model=None):
             raise GeoAlgorithmExecutionException(
                 str(e) + self.tr('\nSee log for more details'))
 
+    def _checkParameterValuesBeforeExecuting(self):
+        for param in self.parameters:
+            if isinstance(param, (ParameterRaster, ParameterVector,
+                          ParameterMultipleInput)):
+                if param.value:
+                    if isinstance(param, ParameterMultipleInput):
+                        inputlayers = param.value.split(';')
+                    else:
+                        inputlayers = [param.value]
+                    for inputlayer in inputlayers:
+                        obj = dataobjects.getObjectFromUri(inputlayer)
+                        if obj is None:
+                            return "Wrong parameter value: " + param.value
+        return self.checkParameterValuesBeforeExecuting()
+
     def runPostExecutionScript(self, progress):
         scriptFile = ProcessingConfig.getSetting(
             ProcessingConfig.POST_EXECUTION_SCRIPT)

python/plugins/processing/core/Processing.py

@@ -327,7 +327,7 @@ def runAlgorithm(algOrName, onFinish, *args):
                         return
                     i = i + 1
 
-        msg = alg.checkParameterValuesBeforeExecuting()
+        msg = alg._checkParameterValuesBeforeExecuting()
         if msg:
             print 'Unable to execute algorithm\n' + msg
             return

python/plugins/processing/gui/AlgorithmDialog.py

@@ -156,7 +156,7 @@ def accept(self):
                     QMessageBox.No)
                 if reply == QMessageBox.No:
                     return
-            msg = self.alg.checkParameterValuesBeforeExecuting()
+            msg = self.alg._checkParameterValuesBeforeExecuting()
             if msg:
                 QMessageBox.warning(
                     self, self.tr('Unable to execute algorithm'), msg)