Log serialization warning when a panel errors. (#1810)

* Log serialization warning when a panel errors.

This will help third party panels identify issues with serializing
the content of their panels in the future, without causing the
entire toolbar to break.

* Change setting name to SUPPRESS_SERIALIZATION_ERRORS

Author: tim-schilling

debug_toolbar/settings.py

@@ -37,6 +37,7 @@
     "PROFILER_CAPTURE_PROJECT_CODE": True,
     "PROFILER_MAX_DEPTH": 10,
     "PROFILER_THRESHOLD_RATIO": 8,
+    "SUPPRESS_SERIALIZATION_ERRORS": True,
     "SHOW_TEMPLATE_CONTEXT": True,
     "SKIP_TEMPLATE_PREFIXES": ("django/forms/widgets/", "admin/widgets/"),
     "SQL_WARNING_THRESHOLD": 500,  # milliseconds

debug_toolbar/store.py

@@ -1,5 +1,6 @@
 import contextlib
 import json
+import logging
 from collections import defaultdict, deque
 from typing import Any, Dict, Iterable
 
@@ -8,6 +9,8 @@
 
 from debug_toolbar import settings as dt_settings
 
+logger = logging.getLogger(__name__)
+
 
 def serialize(data: Any) -> str:
     # If this starts throwing an exceptions, consider
@@ -103,7 +106,14 @@ def delete(cls, request_id: str):
     def save_panel(cls, request_id: str, panel_id: str, data: Any = None):
         """Save the panel data for the given request_id"""
         cls.set(request_id)
-        cls._request_store[request_id][panel_id] = serialize(data)
+        try:
+            cls._request_store[request_id][panel_id] = serialize(data)
+        except TypeError:
+            if dt_settings.get_config()["SUPPRESS_SERIALIZATION_ERRORS"]:
+                log = "Panel (%s) failed to serialized data %s properly."
+                logger.warning(log % (panel_id, data))
+            else:
+                raise
 
     @classmethod
     def panel(cls, request_id: str, panel_id: str) -> Any:

docs/changes.rst

@@ -7,6 +7,8 @@ Serializable (don't include in main)
 * Defines the ``BaseStore`` interface for request storage mechanisms.
 * Added the setting ``TOOLBAR_STORE_CLASS`` to configure the request
   storage mechanism. Defaults to ``debug_toolbar.store.MemoryStore``.
+* Added setting ``SUPPRESS_SERIALIZATION_ERRORS`` to suppress
+  warnings when a ``TypeError`` occurs during a panel's serialization.
 
 
 Pending

docs/configuration.rst

@@ -306,6 +306,15 @@ Panel options
   the nested functions. The threshold is calculated by the root calls'
   cumulative time divided by this ratio.
 
+* ``SUPPRESS_SERIALIZATION_ERRORS``
+
+  Default: ``True``
+
+  If set to ``True`` then panels will log a warning if a ``TypeError`` is
+  raised when attempting to serialize a panel's stats rather than raising an
+  exception.. If set to ``False`` then the ``TypeError`` will be raised. The
+  default will eventually be set to ``False`` and removed entirely.
+
 * ``SHOW_TEMPLATE_CONTEXT``
 
   Default: ``True``

tests/test_store.py

@@ -1,3 +1,5 @@
+import logging
+
 from django.test import TestCase
 from django.test.utils import override_settings
 
@@ -93,6 +95,21 @@ def test_save_panel(self):
         self.assertEqual(list(self.store.request_ids()), ["bar"])
         self.assertEqual(self.store.panel("bar", "bar.panel"), {"a": 1})
 
+    def test_save_panel_serialization_warning(self):
+        """The store should warn the user about a serialization error."""
+        self.assertLogs()
+
+        with self.assertLogs("debug_toolbar.store", level=logging.WARNING) as logs:
+            self.store.save_panel("bar", "bar.panel", {"value": {"foo"}})
+
+        self.assertEqual(
+            logs.output,
+            [
+                "WARNING:debug_toolbar.store:Panel (bar.panel) failed to "
+                "serialized data {'value': {'foo'}} properly."
+            ],
+        )
+
     def test_panel(self):
         self.assertEqual(self.store.panel("missing", "missing"), {})
         self.store.save_panel("bar", "bar.panel", {"a": 1})