[processing] Ensure feature source wrapper always returns direct

layer id/source whenever 'use selected features' is unchecked,
instead of always returning a QgsProcessingFeatureSourceDefinition

(cherry-picked from 6a4d9c9)

python/plugins/processing/gui/wrappers.py

@@ -1187,10 +1187,16 @@ def value(self):
             try:
                 layer = self.combo.currentLayer()
                 if layer is not None:
-                    return QgsProcessingFeatureSourceDefinition(layer.id(), use_selected_features)
+                    if use_selected_features:
+                        return QgsProcessingFeatureSourceDefinition(layer.id(), True)
+                    else:
+                        return layer.id()
                 else:
                     if self.combo.currentText():
-                        return QgsProcessingFeatureSourceDefinition(self.combo.currentText(), use_selected_features)
+                        if use_selected_features:
+                            return QgsProcessingFeatureSourceDefinition(self.combo.currentText(), True)
+                        else:
+                            return self.combo.currentText()
                     else:
                         return None
             except:

python/plugins/processing/tests/GuiTest.py

@@ -119,6 +119,44 @@ def testField(self):
     def testSource(self):
         self.checkConstructWrapper(QgsProcessingParameterFeatureSource('test'), FeatureSourceWidgetWrapper)
 
+        # dummy layer
+        layer = QgsVectorLayer('Point', 'test', 'memory')
+        self.assertTrue(layer.isValid())
+        QgsProject.instance().addMapLayer(layer)
+
+        alg = QgsApplication.processingRegistry().algorithmById('native:centroids')
+        dlg = AlgorithmDialog(alg)
+        param = QgsProcessingParameterFeatureSource('test')
+        wrapper = FeatureSourceWidgetWrapper(param, dlg)
+        widget = wrapper.createWidget()
+
+        # check layer value
+        widget.show()
+        wrapper.setValue(layer.id())
+        self.assertEqual(wrapper.value(), layer.id())
+
+        # check not set
+        wrapper.setValue('')
+        self.assertFalse(wrapper.value())
+
+        # check selected only - expect a QgsProcessingFeatureSourceDefinition
+        wrapper.setValue(layer.id())
+        wrapper.use_selection_checkbox.setChecked(True)
+        value = wrapper.value()
+        self.assertIsInstance(value, QgsProcessingFeatureSourceDefinition)
+        self.assertTrue(value.selectedFeaturesOnly)
+        self.assertEqual(value.source.staticValue(), layer.id())
+
+        # NOT selected only, expect a direct layer id or source value
+        wrapper.use_selection_checkbox.setChecked(False)
+        value = wrapper.value()
+        self.assertEqual(value, layer.id())
+
+        # with non-project layer
+        wrapper.setValue('/home/my_layer.shp')
+        value = wrapper.value()
+        self.assertEqual(value, '/home/my_layer.shp')
+
     def testMapLayer(self):
         self.checkConstructWrapper(QgsProcessingParameterMapLayer('test'), MapLayerWidgetWrapper)