fix: inject Django middleware automatically

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

Author: apotterri

appmap/__init__.py

@@ -5,6 +5,12 @@
 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/flask.py

@@ -44,8 +44,8 @@ def request_params(req):
     return values_dict(params.lists())
 
 
-NP_REGEXP = re.compile(r"<Rule '(.*?)'")
-NP_XLATE = re.compile(r"(?P<l><)|(?P<r>>)")
+NP_PARAMS = re.compile(r"<Rule '(.*?)'")
+NP_PARAM_DELIMS = str.maketrans("<>", "{}")
 
 
 class AppmapFlask(AppmapMiddleware):
@@ -93,15 +93,12 @@ def before_request_main(self, rec, request):
             # Transform request.url to the expected normalized-path form. For example,
             # "/post/<username>/<post_id>/summary" becomes "/post/{username}/{post_id}/summary".
             # Notes:
-            #   * the value of `repr` of this rule begins with "<Repr '/post/<username>/<post_id>/summary'"
+            #   * the value of `repr` of this rule begins with "<Rule '/post/<username>/<post_id>/summary'"
             #   * the variable names in a rule can only contain alphanumerics:
             #     * flask 1: https://github.com/pallets/werkzeug/blob/1dde4b1790f9c46b7122bb8225e6b48a5b22a615/src/werkzeug/routing.py#L143
             #     * flask 2: https://github.com/pallets/werkzeug/blob/99f328cf2721e913bd8a3128a9cdd95ca97c334c/src/werkzeug/routing/rules.py#L56
             r = repr(request.url_rule)
-            np = NP_XLATE.sub(
-                lambda m: "{" if m["l"] else "}" if m["r"] else "",
-                NP_REGEXP.findall(r)[0],
-            )
+            np = NP_PARAMS.findall(r)[0].translate(NP_PARAM_DELIMS)
 
         call_event = HttpServerRequestEvent(
             request_method=request.method,

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

@@ -208,12 +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:"""