Default URLconf detection does not take a prefix into account

[Maarten Breddels]

Hi,

When Django runs onder a prefix (often described by SCRIPT_NAME for cgi/wsgi or root_path in asgi land) the default URLconf is not detected.
The default page shown is then:

Page not found (404)
Request Method:	GET
Request URL:	http://127.0.0.1:8000/_app/m05jjd2cn5gycxqcowk/
Using the URLconf defined in mysite.urls, Django tried these URL patterns, in this order:

admin/
The empty path didn’t match any of these.

You’re seeing this error because you have DEBUG = True in your Django settings file. Change that to False, and Django will display a standard 404 page.

(in this case, the asgi root_path is /_app/m05jjd2cn5gycxqcowk)

While instead, I expected to see the nice default page with

The install worked successfully! Congratulations!

The bug was introduced in ​https://github.com/maartenbreddels/django/commit/0ecb9f6e2514cfd26a678a280d471433375101a3
which uses request.path == '/' for comparison, while request.path_info == '/' was probably the intent. This commit was part of ​https://github.com/maartenbreddels/django/commit/3f1c7b70537330435e2ec2fca9550f7b7fa4372e

Note that request.path includes the prefix (SCRIPT_NAME or root_path), while request.path does not.

I hit this bug when trying to run Django on ​https://py.cafe, a platform that can run web applications on Pyodide.

The project at:
​https://py.cafe/maartenbreddels/django-start-template (which includes this patch)
now runs fine because I monkey-patched it (see ​https://py.cafe/files/maartenbreddels/django-start-template/django_patch.py), showing this is a correct fix.

For technical reasons, we need to run under a prefix (we configure root_path in the asgi scope), and django was giving me a 404. This gave the (false) impression django did not support running under a prefix (StackOverflow falsely confirmed this suspicion).

I already opened a PR at ​https://github.com/django/django/pull/18505 showing the change required. I'm happy to reopen that PR and do minor work on it, but I don't think I'll have the bandwidth to add a test.

Regards,

Maarten Breddels

[Sarah Boyce]

Hi Maarten, thank you for the report!

I have written a test which you should be able to use

tests/view_tests/tests/test_debug.py

@@ -398 +398 @@
             response, "<h1>The install worked successfully! Congratulations!</h1>"
         )
 
+    @override_settings(ROOT_URLCONF="view_tests.default_urls", FORCE_SCRIPT_NAME="/FORCED_PREFIX")
+    def test_default_urlconf_script_name(self):
+        response = self.client.request(**{"path": "/FORCED_PREFIX/"})
+        self.assertContains(
+            response, "<h1>The install worked successfully! Congratulations!</h1>"
+        )
+
     @override_settings(ROOT_URLCONF="view_tests.regression_21530_urls")

[Sarah Boyce <42296566+sarahboyce@…>]

In cdcd604e:

Fixed #35703 -- Made technical_404_response() respect SCRIPT_NAME to return default_urlconf().