fix: inject Django middleware automatically

Import appmap.django at startup, to make sure our middleware gets
injected.

Author: apotterri

appmap/__init__.py

@@ -1,10 +1,16 @@
 """AppMap recorder for Python"""
 from ._implementation import generation  # noqa: F401
 from ._implementation.env import Env  # noqa: F401
-from ._implementation.labels import labels  # noqa: F401
 from ._implementation.importer import instrument_module  # noqa: F401
+from ._implementation.labels import labels  # noqa: F401
 from ._implementation.recording import Recording  # noqa: F401
 
+try:
+    from . import django  # noqa: F401
+except ImportError:
+    # not using django
+    pass
+
 try:
     from . import flask  # noqa: F401
 except ImportError:

appmap/test/data/django/app/settings.py

@@ -10,5 +10,3 @@
 # Must set ROOT_URLCONF else we get
 # AttributeError: 'Settings' object has no attribute 'ROOT_URLCONF'
 ROOT_URLCONF = "app.urls"
-
-MIDDLEWARE = ["appmap.django.Middleware"]

appmap/test/data/django/init/sitecustomize.py

@@ -0,0 +1 @@
+import appmap

appmap/test/test_django.py

@@ -64,7 +64,9 @@ def test_framework_metadata(
 
 
 @pytest.mark.appmap_enabled
-def test_app_can_read_body(client, events, monkeypatch):  # pylint: disable=unused-argument
+def test_app_can_read_body(
+    client, events, monkeypatch
+):  # pylint: disable=unused-argument
     monkeypatch.setenv("APPMAP_RECORD_REQUESTS", "false")
     response = client.post("/echo", json={"test": "json"})
     assert response.content == b'{"test": "json"}'
@@ -206,12 +208,15 @@ def test_middleware_reset(pytester, monkeypatch):
 class TestRecordRequestsDjango(TestRecordRequests):
     @staticmethod
     def server_start_thread(env_vars_str):
+        # Use appmap from our working copy, not the module installed by virtualenv. Add the init
+        # directory so the sitecustomize.py file it contains will be loaded on startup. This
+        # simulates a real installation.
         exec_cmd(
             """
-# use appmap from our working copy, not the module installed by virtualenv
-export PYTHONPATH=`pwd`
+export PYTHONPATH="$PWD"
 
 cd appmap/test/data/django/
+PYTHONPATH="$PYTHONPATH:$PWD/init"
 """
             + env_vars_str
             + """ APPMAP_OUTPUT_DIR=/tmp  python manage.py runserver 127.0.0.1:"""