Fix IndexError: list index out of range

debug_toolbar/panels/templates/panel.py

@@ -141,13 +141,16 @@ def _store_template_info(self, sender, **kwargs):
                                 temp_layer[key] = value
                             finally:
                                 recording(True)
+                    # Execute pformat first - if for some reason pformat/repr
+                    # causes more templates to be rendered, seen/pformat layers
+                    # will still be consistent
+                    pformatted = pformat(temp_layer)
                     # Refs GitHub issue #910
                     # If we've not seen the layer before then we will add it
                     # so that if we see it again we can skip formatting it.
                     self.seen_layers.append(key_values)
                     # Note: this *ought* to be len(...) - 1 but let's be safe.
                     index = self.seen_layers.index(key_values)
-                    pformatted = pformat(temp_layer)
                     # Note: this *ought* to be len(...) - 1 but let's be safe.
                     self.pformat_layers.insert(index, pformatted)
                     context_list.append(pformatted)

tests/forms.py

@@ -0,0 +1,9 @@
+from django import forms
+from django.contrib.auth.models import User
+
+
+class TemplateReprForm(forms.Form):
+    user = forms.ModelChoiceField(queryset=User.objects.all())
+
+    def __repr__(self):
+        return str(self)

tests/panels/test_template.py

@@ -3,6 +3,7 @@
 from django.test import TestCase, override_settings
 
 from ..base import BaseTestCase
+from ..forms import TemplateReprForm
 from ..models import NonAsciiRepr
 
 
@@ -35,6 +36,18 @@ def test_queryset_hook(self):
         self.assertIn("<<queryset of auth.User>>", ctx)
         self.assertIn("<<triggers database query>>", ctx)
 
+    def test_template_repr(self):
+        # Force widget templates to be included
+        self.toolbar.config["SKIP_TEMPLATE_PREFIXES"] = ()
+
+        User.objects.create(username="admin")
+        bad_repr = TemplateReprForm()
+        t = Template("{{ bad_repr }}")
+        c = Context({"bad_repr": bad_repr})
+        html = t.render(c)
+        self.assertIsNotNone(html)
+        self.assertValidHTML(html)
+
     def test_object_with_non_ascii_repr_in_context(self):
         response = self.panel.process_request(self.request)
         t = Template("{{ object }}")