[fix] Fixes by @coderabbitai

Author: pandafy

openwisp_users/management/commands/export_users.py

@@ -170,4 +170,6 @@ def _get_field_value(self, user, field):
                 self._normalize_value(self._get_nested_attr(attr, f)) for f in subfields
             )
         val = self._get_nested_attr(user, name)
+        if isinstance(val, (QuerySet, BaseManager)):
+            return ""
         return self._normalize_value(val)

openwisp_users/settings.py

@@ -16,6 +16,8 @@
 
 
 def _export_organizations(user):
+    # _export_organizations reads user.organizations_dict which is populated
+    # when the user is added to the organization.
     return ",".join(
         f'({org_id},{perm["is_admin"]})'
         for org_id, perm in user.organizations_dict.items()

openwisp_users/tests/test_commands.py

@@ -191,7 +191,7 @@ def _broken_callable(user):
         ):
             # the command wraps callable errors in CommandError with callable name
             call_command("export_users", filename=self.temp_file.name, stderr=stderr)
-        self.assertIn("Error calling function '", str(context.exception) or "")
+        self.assertIn("Error calling function '", str(context.exception))
 
     @patch.object(
         app_settings,
@@ -265,3 +265,10 @@ class FakeUser:
 
         result = Command()._get_field_value(FakeUser(), "intermediate.sub_field")
         self.assertEqual(result, "")
+
+    def test_plain_relation_field_returns_empty_string(self):
+        org = self._create_org(name="org1")
+        user = self._create_user()
+        self._create_org_user(organization=org, user=user, is_admin=True)
+        result = Command()._get_field_value(user, "openwisp_users_organizationuser")
+        self.assertEqual(result, "")