[processing] Fix processing.runAndLoadResults

Fixes #21551

python/plugins/processing/gui/Postprocessing.py

@@ -96,6 +96,8 @@ def handleAlgorithmResults(alg, context, feedback=None, showResults=True, parame
                 scope = QgsExpressionContextScope()
                 expcontext.appendScope(scope)
                 for out in alg.outputDefinitions():
+                    if out.name() not in parameters:
+                        continue
                     outValue = parameters[out.name()]
                     if hasattr(outValue, "sink"):
                         outValue = outValue.sink.valueAsString(expcontext)[0]

python/plugins/processing/tests/ProcessingGeneralTest.py

@@ -32,7 +32,8 @@
 from qgis.core import (QgsApplication,
                        QgsProcessing,
                        QgsProcessingContext,
-                       QgsVectorLayer)
+                       QgsVectorLayer,
+                       QgsProject)
 from qgis.PyQt import sip
 from qgis.analysis import (QgsNativeAlgorithms)
 from qgis.testing import start_app, unittest
@@ -91,6 +92,26 @@ def testRun(self):
         gc.collect()
         self.assertTrue(sip.isdeleted(layer))
 
+    def testRunAndLoadResults(self):
+        QgsProject.instance().removeAllMapLayers()
+        context = QgsProcessingContext()
+
+        # try running an alg using processing.runAndLoadResults - ownership of result layer should be transferred to
+        # project, and layer should be present in project
+        res = processing.runAndLoadResults('qgis:buffer',
+                                           {'DISTANCE': 1, 'INPUT': points(), 'OUTPUT': QgsProcessing.TEMPORARY_OUTPUT},
+                                           context=context)
+        self.assertIn('OUTPUT', res)
+        # output should be the layer path
+        self.assertIsInstance(res['OUTPUT'], str)
+
+        self.assertEqual(context.layersToLoadOnCompletion()[res['OUTPUT']].project, QgsProject.instance())
+        layer = QgsProject.instance().mapLayer(res['OUTPUT'])
+        self.assertIsInstance(layer, QgsVectorLayer)
+
+        # Python should NOT have ownership
+        self.assertFalse(sip.ispyowned(layer))
+
 
 if __name__ == '__main__':
     nose2.main()