Fixed #33747 -- Added exception notes to the technical 500 debug page.

django/views/debug.py

@@ -396,6 +396,8 @@ class ExceptionReporter:
             c["exception_type"] = self.exc_type.__name__
         if self.exc_value:
             c["exception_value"] = str(self.exc_value)
+            if exc_notes := getattr(self.exc_value, "__notes__", None):
+                c["exception_notes"] = "\n" + "\n".join(exc_notes)
         if frames:
             c["lastframe"] = frames[-1]
         return c

django/views/templates/technical_500.html

@@ -100,7 +100,7 @@
 <div id="summary">
   <h1>{% if exception_type %}{{ exception_type }}{% else %}Report{% endif %}
       {% if request %} at {{ request.path_info }}{% endif %}</h1>
-  <pre class="exception_value">{% if exception_value %}{{ exception_value|force_escape }}{% else %}No exception message supplied{% endif %}</pre>
+  <pre class="exception_value">{% if exception_value %}{{ exception_value|force_escape }}{% if exception_notes %}{{ exception_notes }}{% endif %}{% else %}No exception message supplied{% endif %}</pre>
   <table class="meta">
 {% if request %}
     <tr>
@@ -330,7 +330,7 @@ During handling of the above exception ({{ frame.exc_cause|force_escape }}), ano
 {% if frame.context_line %}    {% spaceless %}{{ frame.context_line }}{% endspaceless %}{% endif %}{% elif forloop.first %}None{% else %}Traceback: None{% endif %}{% endfor %}
 
 Exception Type: {{ exception_type }}{% if request %} at {{ request.path_info }}{% endif %}
-Exception Value: {{ exception_value|force_escape }}
+Exception Value: {{ exception_value|force_escape }}{% if exception_notes %}{{ exception_notes }}{% endif %}
 </textarea>
   <br><br>
   <input type="submit" value="Share this traceback on a public website">

django/views/templates/technical_500.txt

@@ -34,7 +34,7 @@ Traceback (most recent call last):
 {% if frame.context_line %}    {% spaceless %}{{ frame.context_line }}{% endspaceless %}{% endif %}{% elif forloop.first %}None{% else %}Traceback: None{% endif %}
 {% endfor %}
 {% if exception_type %}Exception Type: {{ exception_type }}{% if request %} at {{ request.path_info }}{% endif %}
-{% if exception_value %}Exception Value: {{ exception_value }}{% endif %}{% endif %}{% endif %}
+{% if exception_value %}Exception Value: {{ exception_value }}{% endif %}{% if exception_notes %}{{ exception_notes }}{% endif %}{% endif %}{% endif %}
 {% if raising_view_name %}Raised during: {{ raising_view_name }}{% endif %}
 {% if request %}Request information:
 {% if user_str %}USER: {{ user_str }}{% endif %}

docs/releases/4.2.txt

@@ -158,7 +158,7 @@ Email
 Error Reporting
 ~~~~~~~~~~~~~~~
 
-* ...
+* The debug page now shows :pep:`exception notes <678>` on Python 3.11+.
 
 File Storage
 ~~~~~~~~~~~~

tests/view_tests/tests/test_debug.py

@@ -7,7 +7,7 @@ import tempfile
 import threading
 from io import StringIO
 from pathlib import Path
-from unittest import mock, skipIf
+from unittest import mock, skipIf, skipUnless
 
 from django.core import mail
 from django.core.files.uploadedfile import SimpleUploadedFile
@@ -22,6 +22,7 @@ from django.urls.converters import IntConverter
 from django.utils.functional import SimpleLazyObject
 from django.utils.regex_helper import _lazy_re_compile
 from django.utils.safestring import mark_safe
+from django.utils.version import PY311
 from django.views.debug import (
     CallableSettingWrapper,
     ExceptionCycleWarning,
@@ -659,6 +660,40 @@ class ExceptionReporterTests(SimpleTestCase):
             text,
         )
 
+    @skipUnless(PY311, "Exception notes were added in Python 3.11.")
+    def test_exception_with_notes(self):
+        request = self.rf.get("/test_view/")
+        try:
+            try:
+                raise RuntimeError("Oops")
+            except Exception as err:
+                err.add_note("First Note")
+                err.add_note("Second Note")
+                err.add_note(mark_safe("<script>alert(1);</script>"))
+                raise err
+        except Exception:
+            exc_type, exc_value, tb = sys.exc_info()
+
+        reporter = ExceptionReporter(request, exc_type, exc_value, tb)
+        html = reporter.get_traceback_html()
+        self.assertIn(
+            '<pre class="exception_value">Oops\nFirst Note\nSecond Note\n'
+            "&lt;script&gt;alert(1);&lt;/script&gt;</pre>",
+            html,
+        )
+        self.assertIn(
+            "Exception Value: Oops\nFirst Note\nSecond Note\n"
+            "&lt;script&gt;alert(1);&lt;/script&gt;",
+            html,
+        )
+
+        text = reporter.get_traceback_text()
+        self.assertIn(
+            "Exception Value: Oops\nFirst Note\nSecond Note\n"
+            "<script>alert(1);</script>",
+            text,
+        )
+
     def test_mid_stack_exception_without_traceback(self):
         try:
             try: