App: fix restoring the attributes of a dynamic property

For more details see: https://forum.freecadweb.org/viewtopic.php?p=591465#p591465

src/Mod/Test/Document.py

@@ -377,6 +377,30 @@ class DocumentBasicCases(unittest.TestCase):
     obj1.Link = obj2
     self.assertEqual(obj1.MustExecute, False)
 
+  def testAttributeOfDynamicProperty(self):
+    obj = self.Doc.addObject("App::FeaturePython", "Obj")
+    # Prop_NoPersist is the enum with the highest value
+    max_value = FreeCAD.PropertyType.Prop_NoPersist
+    list_of_types = []
+    for i in range(0, max_value + 1):
+      obj.addProperty("App::PropertyString", "String" + str(i), "", "", i)
+      list_of_types.append(obj.getTypeOfProperty("String" + str(i)))
+
+    # saving and restoring
+    SaveName = tempfile.gettempdir() + os.sep + "CreateTest.FCStd"
+    self.Doc.saveAs(SaveName)
+    FreeCAD.closeDocument("CreateTest")
+    self.Doc = FreeCAD.open(SaveName)
+
+    obj = self.Doc.ActiveObject
+    for i in range(0, max_value):
+      types = obj.getTypeOfProperty("String" + str(i))
+      self.assertEqual(list_of_types[i], types)
+
+    # A property with flag Prop_NoPersist won't be saved to the file
+    with self.assertRaises(AttributeError):
+      obj.getTypeOfProperty("String" + str(max_value))
+
   def testNotification_Issue2902Part2(self):
     o = self.Doc.addObject("App::FeatureTest","test")