panels(templates): avoid evaluating LazyObject

LazyObject is typically used for something expensive to evaluate, so avoid evaluating it just for showing it in the debug toolbar.

debug_toolbar/panels/templates/panel.py

@@ -96,10 +96,15 @@ def _store_template_info(self, sender, **kwargs):
  if pformatted is None:
  temp_layer = {}
  for key, value in context_layer.items():
+ # Do not force evaluating LazyObject
+ if hasattr(value, "_wrapped"):
+ # SimpleLazyObject has __repr__ which includes actual value
+ # if it has been already evaluated
+ temp_layer[key] = repr(value)
  # Replace any request elements - they have a large
  # Unicode representation and the request data is
  # already made available from the Request panel.
- if isinstance(value, http.HttpRequest):
+ elif isinstance(value, http.HttpRequest):
  temp_layer[key] = "<<request>>"
  # Replace the debugging sql_queries element. The SQL
  # data is already made available from the SQL panel.

docs/changes.rst

@@ -5,6 +5,7 @@ Pending
 -------
 
 * Removed outdated third-party panels from the list.
+* Avoid evaluating ``LazyObject`` in the templates panel.
 
 4.2.0 (2023-08-10)
 ------------------

tests/panels/test_template.py

@@ -2,6 +2,7 @@
 from django.contrib.auth.models import User
 from django.template import Context, RequestContext, Template
 from django.test import override_settings
+from django.utils.functional import SimpleLazyObject
 
 from ..base import BaseTestCase, IntegrationTestCase
 from ..forms import TemplateReprForm
@@ -109,6 +110,14 @@ def test_empty_context(self):
  ["{'False': False, 'None': None, 'True': True}"],
  )
 
+ def test_lazyobject(self):
+ response = self.panel.process_request(self.request)
+ t = Template("")
+ c = Context({"lazy": SimpleLazyObject(lambda: "lazy_value")})
+ t.render(c)
+ self.assertNotIn("lazy_value", self.panel.content)
+
+
 
 @override_settings(
  DEBUG=True, DEBUG_TOOLBAR_PANELS=["debug_toolbar.panels.templates.TemplatesPanel"]