Add layer to QGIS 3 map from processing script

Question

I would load to QGIS map a vector layer from processing script. I'm trying to use QgsProject.instance().addMapLayer(layer). It works if I run the code from pyqgis console:

layer=QgsVectorLayer('fileName.shp',"name","ogr")
if not layer.isValid():
   print('layer failed to load')
QgsProject.instance().addMapLayer(layer)

but it cannot works if I run the same from processing script. No error alerts are shown.

Answer 1

From a previous answer in another processing context, the following should do what you want

context.temporaryLayerStore().addMapLayer(layer)
context.addLayerToLoadOnCompletion(
            layer.id(),
            QgsProcessingContext.LayerDetails('SQL layer',
                                              context.project(),
                                              'LAYER'))

See both method temporaryLayerStore doc and method addLayerToLoadOnCompletion doc