panels(templates): postpone context processing

- this makes it show evaluated querysets which were used in the template
- removes completely context processing when SHOW_TEMPLATE_CONTEXT is
  disabled

debug_toolbar/panels/templates/panel.py

@@ -83,58 +83,11 @@ def _store_template_info(self, sender, **kwargs):
  if is_debug_toolbar_template:
  return
 
- context_list = []
- for context_layer in context.dicts:
- if hasattr(context_layer, "items") and context_layer:
- # Check if the layer is in the cache.
- pformatted = None
- for key_values, _pformatted in self.pformat_layers:
- if key_values == context_layer:
- pformatted = _pformatted
- break
-
- if pformatted is None:
- temp_layer = {}
- for key, value in context_layer.items():
- # 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):
- temp_layer[key] = "<<request>>"
- # Replace the debugging sql_queries element. The SQL
- # data is already made available from the SQL panel.
- elif key == "sql_queries" and isinstance(value, list):
- temp_layer[key] = "<<sql_queries>>"
- # Replace LANGUAGES, which is available in i18n context
- # processor
- elif key == "LANGUAGES" and isinstance(value, tuple):
- temp_layer[key] = "<<languages>>"
- # QuerySet would trigger the database: user can run the
- # query from SQL Panel
- elif isinstance(value, (QuerySet, RawQuerySet)):
- temp_layer[key] = "<<{} of {}>>".format(
- value.__class__.__name__.lower(),
- value.model._meta.label,
- )
- else:
- token = allow_sql.set(False) # noqa: FBT003
- try:
- saferepr(value) # this MAY trigger a db query
- except SQLQueryTriggered:
- temp_layer[key] = "<<triggers database query>>"
- except UnicodeEncodeError:
- temp_layer[key] = "<<Unicode encode error>>"
- except Exception:
- temp_layer[key] = "<<unhandled exception>>"
- else:
- temp_layer[key] = value
- finally:
- allow_sql.reset(token)
- pformatted = pformat(temp_layer)
- self.pformat_layers.append((context_layer, pformatted))
- context_list.append(pformatted)
-
- kwargs["context"] = context_list
+ kwargs["context"] = [
+ context_layer
+ for context_layer in context.dicts
+ if hasattr(context_layer, "items") and context_layer
+ ]
  kwargs["context_processors"] = getattr(context, "context_processors", None)
  self.templates.append(kwargs)
 
@@ -167,6 +120,59 @@ def enable_instrumentation(self):
  def disable_instrumentation(self):
  template_rendered.disconnect(self._store_template_info)
 
+ def process_context_list(self, context_layers):
+ context_list = []
+ for context_layer in context_layers:
+ # Check if the layer is in the cache.
+ pformatted = None
+ for key_values, _pformatted in self.pformat_layers:
+ if key_values == context_layer:
+ pformatted = _pformatted
+ break
+
+ if pformatted is None:
+ temp_layer = {}
+ for key, value in context_layer.items():
+ # 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):
+ temp_layer[key] = "<<request>>"
+ # Replace the debugging sql_queries element. The SQL
+ # data is already made available from the SQL panel.
+ elif key == "sql_queries" and isinstance(value, list):
+ temp_layer[key] = "<<sql_queries>>"
+ # Replace LANGUAGES, which is available in i18n context
+ # processor
+ elif key == "LANGUAGES" and isinstance(value, tuple):
+ temp_layer[key] = "<<languages>>"
+ # QuerySet would trigger the database: user can run the
+ # query from SQL Panel
+ elif isinstance(value, (QuerySet, RawQuerySet)):
+ temp_layer[key] = "<<{} of {}>>".format(
+ value.__class__.__name__.lower(),
+ value.model._meta.label,
+ )
+ else:
+ token = allow_sql.set(False) # noqa: FBT003
+ try:
+ saferepr(value) # this MAY trigger a db query
+ except SQLQueryTriggered:
+ temp_layer[key] = "<<triggers database query>>"
+ except UnicodeEncodeError:
+ temp_layer[key] = "<<Unicode encode error>>"
+ except Exception:
+ temp_layer[key] = "<<unhandled exception>>"
+ else:
+ temp_layer[key] = value
+ finally:
+ allow_sql.reset(token)
+ pformatted = pformat(temp_layer)
+ self.pformat_layers.append((context_layer, pformatted))
+ context_list.append(pformatted)
+
+ return context_list
+
  def generate_stats(self, request, response):
  template_context = []
  for template_data in self.templates:
@@ -182,8 +188,11 @@ def generate_stats(self, request, response):
  info["template"] = template
  # Clean up context for better readability
  if self.toolbar.config["SHOW_TEMPLATE_CONTEXT"]:
- context_list = template_data.get("context", [])
- info["context"] = "\n".join(context_list)
+ if "context_list" not in template_data:
+ template_data["context_list"] = self.process_context_list(
+ template_data.get("context", [])
+ )
+ info["context"] = "\n".join(template_data["context_list"])
  template_context.append(info)
 
  # Fetch context_processors/template_dirs from any template

docs/changes.rst

@@ -5,6 +5,8 @@ Pending
 -------
 
 * Removed outdated third-party panels from the list.
+* Postponed context process in templates panel to include lazy evaluated
+ content.
 
 4.2.0 (2023-08-10)
 ------------------

tests/panels/test_template.py

@@ -21,6 +21,7 @@ def tearDown(self):
  super().tearDown()
 
  def test_queryset_hook(self):
+ response = self.panel.process_request(self.request)
  t = Template("No context variables here!")
  c = Context(
  {
@@ -29,12 +30,13 @@ def test_queryset_hook(self):
  }
  )
  t.render(c)
+ self.panel.generate_stats(self.request, response)
 
  # ensure the query was NOT logged
  self.assertEqual(len(self.sql_panel._queries), 0)
 
  self.assertEqual(
- self.panel.templates[0]["context"],
+ self.panel.templates[0]["context_list"],
  [
  "{'False': False, 'None': None, 'True': True}",
  "{'deep_queryset': '<<triggers database query>>',\n"
@@ -99,13 +101,15 @@ def test_disabled(self):
  self.assertFalse(self.panel.enabled)
 
  def test_empty_context(self):
+ response = self.panel.process_request(self.request)
  t = Template("")
  c = Context({})
  t.render(c)
+ self.panel.generate_stats(self.request, response)
 
  # Includes the builtin context but not the empty one.
  self.assertEqual(
- self.panel.templates[0]["context"],
+ self.panel.templates[0]["context_list"],
  ["{'False': False, 'None': None, 'True': True}"],
  )