Navigation: Related field support to SourceColumn

Add support to the SourceColumn class to resolve related fields
using the double underscore as separator. Columns that use related
no longer have to use throw away lambdas.

Signed-off-by: Roberto Rosario <Roberto.Rosario@mayan-edms.com>

mayan/apps/common/utils.py

@@ -7,6 +7,7 @@ import tempfile
 import types
 
 from django.conf import settings
+from django.db.models.constants import LOOKUP_SEP
 from django.urls import resolve as django_resolve
 from django.urls.base import get_script_prefix
 from django.utils.datastructures import MultiValueDict
@@ -129,27 +130,34 @@ def resolve(path, urlconf=None):
     return django_resolve(path=path, urlconf=urlconf)
 
 
-def return_attrib(obj, attrib, arguments=None):
+def resolve_attribute(obj, attrib, arguments=None):
     if isinstance(attrib, types.FunctionType):
         return attrib(obj)
-    elif isinstance(
-        obj, dict_type
-    ) or isinstance(obj, dictionary_type):
+    elif isinstance(obj, dict_type) or isinstance(obj, dictionary_type):
         return obj[attrib]
     else:
-        result = reduce_function(getattr, attrib.split('.'), obj)
-        if isinstance(result, types.MethodType):
-            if arguments:
-                return result(**arguments)
+        try:
+            result = reduce_function(getattr, attrib.split('.'), obj)
+            if isinstance(result, types.MethodType):
+                if arguments:
+                    return result(**arguments)
+                else:
+                    return result()
             else:
-                return result()
-        else:
-            return result
+                return result
+        except AttributeError:
+            if LOOKUP_SEP in attrib:
+                attrib = attrib.replace(LOOKUP_SEP, '.')
+                return resolve_attribute(
+                    obj=obj, attrib=attrib, arguments=arguments
+                )
+            else:
+                raise
 
 
 def return_related(instance, related_field):
     """
-    This functions works in a similar method to return_attrib but is
+    This functions works in a similar method to resolve_attribute but is
     meant for related models. Support multiple levels of relationship
     using double underscore.
     """