fix(spotlight): More defensive Django spotlight middleware injection (#3665)

Turns out `settings.MIDDLEWARE` does not have to be a `list`. This causes issues as not all iterables support appending items to them. This PR leverages `itertools.chain` along with `type(settings.MIDDLEWARE)` to extend the middleware list while keeping its original type. It also adds a try-except block around the injection code to make sure it doesn't block anything further down in the unexpected case that it fails.

Author: BYK

sentry_sdk/spotlight.py

@@ -5,6 +5,8 @@
 import urllib.error
 import urllib3
 
+from itertools import chain
+
 from typing import TYPE_CHECKING
 
 if TYPE_CHECKING:
@@ -13,11 +15,12 @@
     from typing import Dict
     from typing import Optional
 
-from sentry_sdk.utils import logger, env_to_bool
+from sentry_sdk.utils import logger, env_to_bool, capture_internal_exceptions
 from sentry_sdk.envelope import Envelope
 
 
 DEFAULT_SPOTLIGHT_URL = "http://localhost:8969/stream"
+DJANGO_SPOTLIGHT_MIDDLEWARE_PATH = "sentry_sdk.spotlight.SpotlightMiddleware"
 
 
 class SpotlightClient:
@@ -112,9 +115,16 @@ def setup_spotlight(options):
     else:
         return None
 
-    if settings is not None and env_to_bool(
-        os.environ.get("SENTRY_SPOTLIGHT_ON_ERROR", "1")
+    if (
+        settings is not None
+        and settings.DEBUG
+        and env_to_bool(os.environ.get("SENTRY_SPOTLIGHT_ON_ERROR", "1"))
     ):
-        settings.MIDDLEWARE.append("sentry_sdk.spotlight.SpotlightMiddleware")
+        with capture_internal_exceptions():
+            middleware = settings.MIDDLEWARE
+            if DJANGO_SPOTLIGHT_MIDDLEWARE_PATH not in middleware:
+                settings.MIDDLEWARE = type(middleware)(
+                    chain(middleware, (DJANGO_SPOTLIGHT_MIDDLEWARE_PATH,))
+                )
 
     return SpotlightClient(url)

tests/integrations/django/test_basic.py

@@ -1247,6 +1247,7 @@ def test_ensures_spotlight_middleware_when_spotlight_is_enabled(sentry_init, set
     Test that ensures if Spotlight is enabled, relevant SpotlightMiddleware
     is added to middleware list in settings.
     """
+    settings.DEBUG = True
     original_middleware = frozenset(settings.MIDDLEWARE)
 
     sentry_init(integrations=[DjangoIntegration()], spotlight=True)
@@ -1263,6 +1264,7 @@ def test_ensures_no_spotlight_middleware_when_env_killswitch_is_false(
     Test that ensures if Spotlight is enabled, but is set to a falsy value
     the relevant SpotlightMiddleware is NOT added to middleware list in settings.
     """
+    settings.DEBUG = True
     monkeypatch.setenv("SENTRY_SPOTLIGHT_ON_ERROR", "no")
 
     original_middleware = frozenset(settings.MIDDLEWARE)
@@ -1281,6 +1283,8 @@ def test_ensures_no_spotlight_middleware_when_no_spotlight(
     Test that ensures if Spotlight is not enabled
     the relevant SpotlightMiddleware is NOT added to middleware list in settings.
     """
+    settings.DEBUG = True
+
     # We should NOT have the middleware even if the env var is truthy if Spotlight is off
     monkeypatch.setenv("SENTRY_SPOTLIGHT_ON_ERROR", "1")