[QGIS-Developer] Using memory layer in Processing with SAGA and GRASS

[matteo]

Hi devs,

sorry if I missed something on this topic, but it seems that it is not
possible using memory layer when running algorithms from the console.

A simple example should explain everything:

# QGIS
parameters = {
    'INPUT' : 'big',
    'OVERLAY': 'small',
    'OUTPUT':'memory:'
}

result = processing.run("qgis:difference", parameters)
QgsProject.instance().addMapLayer(result['OUTPUT'])

# SAGA

parameters_saga = {
    'A': 'big',
    'B': 'small',
    'SPLIT': True,
    'RESULT': 'memory:'
}

result_saga = processing.run("saga:difference", parameters_saga)

# nothing is added with this code
QgsProject.instance().addMapLayer(result_saga['RESULT'])


with the code of above I noticed that the big difference is in:

# QGIS
result['OUTPUT']
<qgis._core.QgsVectorLayer object at 0x7f92a8a479d8

and

#SAGA
result_saga['RESULT']
'memory:'


the same happens with GRASS. The algorithms work fine if the result is
saved as file

Am I missing something for SAGA and GRASS?

Thanks for all the suggestions

Cheers

Matteo