fix: handle a tuple value for settings.MIDDLEWARE

Django is fine with settings.MIDDLEWARE being either a tuple or a list,
but we were expecting a list. Now, we can handle either.

Author: apotterri

appmap/django.py

@@ -6,6 +6,7 @@
 """
 
 import json
+import logging
 import re
 import sys
 import time
@@ -37,6 +38,8 @@
 from ._implementation.web_framework import AppmapMiddleware
 from ._implementation.web_framework import TemplateHandler as BaseTemplateHandler
 
+logger = logging.getLogger(__name__)
+
 
 def parse_pg_version(version):
     """Transform postgres version number like 120005 to a tuple like 12.0.5."""
@@ -296,10 +299,23 @@ def after_request_main(self, rec, response, start, call_event_id):
 def inject_middleware():
     """Make sure AppMap middleware is added to the stack"""
     if "appmap.django.Middleware" not in settings.MIDDLEWARE:
+        stack = list(settings.MIDDLEWARE)
+
         new_middleware = ["appmap.django.Middleware"]
         if DetectEnabled.should_enable("remote"):
             new_middleware.insert(0, "appmap._implementation.django.RemoteRecording")
-        settings.MIDDLEWARE[0:0] = new_middleware
+
+        stack[0:0] = new_middleware
+        # Django is ok with settings.MIDDLEWARE being any kind iterable. Update it, without changing
+        # its type, if we can.
+        if isinstance(settings.MIDDLEWARE, list):
+            settings.MIDDLEWARE = stack
+        elif isinstance(settings.MIDDLEWARE, tuple):
+            settings.MIDDLEWARE = tuple(stack)
+        else:
+            logger.warning(
+                f"Don't know how to update settings.MIDDLEWARE of type {type(settings.MIDDLEWARE)}, recording is not enabled."
+            )
 
 
 original_load_middleware = BaseHandler.load_middleware

appmap/test/data/django/test/test_app.py

@@ -1,13 +1,19 @@
 import app
+import pytest
 from django.core.handlers.base import BaseHandler
 from django.test import Client
 
 
-def test_middleware(rf, settings):
-    settings.MIDDLEWARE = ["app.middleware.hello_world"]
-    request = rf.get("/")
+@pytest.mark.parametrize(
+    "mware", [["app.middleware.hello_world"], ("app.middleware.hello_world",)]
+)
+def test_middleware(rf, settings, mware):
+    settings.MIDDLEWARE = mware
+    orig_type = type(settings.MIDDLEWARE)
+    request = rf.get("/_appmap/record")
     handler = BaseHandler()
     handler.load_middleware()
+    assert type(settings.MIDDLEWARE) == orig_type
     response = handler.get_response(request)
     assert response.status_code == 200
 

appmap/test/test_django.py

@@ -191,7 +191,8 @@ def test_middleware_reset(pytester, monkeypatch):
 
     # To really check middleware reset, the tests must run in order,
     # so disable randomly.
-    pytester.runpytest("-svv", "-p", "no:randomly")
+    result = pytester.runpytest("-svv", "-p", "no:randomly")
+    result.assert_outcomes(passed=3, failed=0, errors=0)
 
     # Look for the http_server_request event in test_app's appmap. If
     # middleware reset is broken, it won't be there.