Make QGIS Line Intersections algorithm able to keep all attributes.

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

@@ -30,7 +30,8 @@
 
 from qgis.PyQt.QtGui import QIcon
 
-from qgis.core import Qgis, QgsFeatureRequest, QgsFeature, QgsGeometry, QgsWkbTypes
+from qgis.core import (Qgis, QgsFeatureRequest, QgsFeature, QgsGeometry,
+                       QgsWkbTypes, QgsFields)
 
 from processing.core.GeoAlgorithm import GeoAlgorithm
 from processing.core.parameters import ParameterVector
@@ -63,12 +64,12 @@ def defineCharacteristics(self):
                                           self.tr('Intersect layer'), [dataobjects.TYPE_VECTOR_LINE]))
         self.addParameter(ParameterTableField(
             self.FIELD_A,
-            self.tr('Input unique ID field'),
+            self.tr('Input field to keep (leave as [not set] to keep all fields)'),
             self.INPUT_A,
             optional=True))
         self.addParameter(ParameterTableField(
             self.FIELD_B,
-            self.tr('Intersect unique ID field'),
+            self.tr('Intersect field to keep (leave as [not set] to keep all fields)'),
             self.INPUT_B,
             optional=True))
 
@@ -83,10 +84,22 @@ def processAlgorithm(self, progress):
         idxA = layerA.fields().lookupField(fieldA)
         idxB = layerB.fields().lookupField(fieldB)
 
-        fieldList = [layerA.fields()[idxA],
-                     layerB.fields()[idxB]]
+        if idxA != -1:
+            fieldListA = QgsFields()
+            fieldListA.append(layerA.fields()[idxA])
+        else:
+            fieldListA = layerA.fields()
 
-        writer = self.getOutputFromName(self.OUTPUT).getVectorWriter(fieldList,
+        if idxB != -1:
+            fieldListB = QgsFields()
+            fieldListB.append(layerB.fields()[idxB])
+        else:
+            fieldListB = layerB.fields()
+
+        fieldListB = vector.testForUniqueness(fieldListA, fieldListB)
+        fieldListA.extend(fieldListB)
+
+        writer = self.getOutputFromName(self.OUTPUT).getVectorWriter(fieldListA,
                                                                      QgsWkbTypes.Point, layerA.crs())
 
         spatialIndex = vector.spatialindex(layerB)
@@ -115,7 +128,11 @@ def processAlgorithm(self, progress):
 
                     points = []
                     attrsA = inFeatA.attributes()
+                    if idxA != -1:
+                        attrsA = [attrsA[idxA]]
                     attrsB = inFeatB.attributes()
+                    if idxB != -1:
+                        attrsB = [attrsB[idxB]]
 
                     if engine.intersects(tmpGeom.geometry()):
                         tempGeom = inGeom.intersection(tmpGeom)
@@ -127,8 +144,8 @@ def processAlgorithm(self, progress):
 
                             for j in points:
                                 outFeat.setGeometry(tempGeom.fromPoint(j))
-                                outFeat.setAttributes([attrsA[idxA],
-                                                       attrsB[idxB]])
+                                attrsA.extend(attrsB)
+                                outFeat.setAttributes(attrsA)
                                 writer.addFeature(outFeat)
 
             progress.setPercentage(int(current * total))