Make 'merge' algorithm store the original layer name and source

Author: nyalldawson

python/plugins/processing/algs/help/qgis.yaml

@@ -312,7 +312,7 @@ qgis:mergelines: >
 qgis:mergevectorlayers: >
   This algorithm combines multiple vector layers of the same geometry type into a single one.
 
-  If attributes tables are different, the attribute table of the resulting layer will contain the attributes from both input layers.
+  If attributes tables are different, the attribute table of the resulting layer will contain the attributes from all input layers. New attributes will be added for the original layer name and source.
 
   The layers will all be reprojected to match the coordinate reference system of the first input layer.
 

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

@@ -30,6 +30,7 @@
 from qgis.PyQt.QtGui import QIcon
 from qgis.PyQt.QtCore import QVariant
 from qgis.core import (QgsFields,
+                       QgsField,
                        QgsFeatureRequest,
                        QgsProcessingUtils,
                        QgsProcessingParameterMultipleLayers,
@@ -104,6 +105,15 @@ def processAlgorithm(self, parameters, context, feedback):
                 if not found:
                     fields.append(sfield)
 
+        add_layer_field = False
+        if fields.lookupField('layer') < 0:
+            fields.append(QgsField('layer', QVariant.String, '', 100))
+            add_layer_field = True
+        add_path_field = False
+        if fields.lookupField('path') < 0:
+            fields.append(QgsField('path', QVariant.String, '', 200))
+            add_path_field = True
+
         total = 100.0 / totalFeatureCount
         dest_crs = layers[0].crs()
         (sink, dest_id) = self.parameterAsSink(parameters, self.OUTPUT, context,
@@ -118,6 +128,13 @@ def processAlgorithm(self, parameters, context, feedback):
                 sattributes = feature.attributes()
                 dattributes = []
                 for dindex, dfield in enumerate(fields):
+                    if add_layer_field and dfield.name() == 'layer':
+                        dattributes.append(layer.name())
+                        continue
+                    if add_path_field and dfield.name() == 'path':
+                        dattributes.append(layer.publicSource())
+                        continue
+
                     if (dfield.type() == QVariant.Int, QVariant.UInt, QVariant.LongLong, QVariant.ULongLong):
                         dattribute = 0
                     elif (dfield.type() == QVariant.Double):