OPTIONS Request made to domain root (/) on ddev nginx throws a 405 - We see access.log but the request is not forwarded to index.php

Edit

Corrected a couple of assumptions with more testing (and altered title to reflect). The issue seems to be specific to the nginx config on DDev, with the server not correctly passing "OPTIONS / HTTP/1.1" requests to the web root (despite all pathing and postman requests working fine).

further edit

Refined question to best be found for those with the same issue.

Q: Whats happening?

Requests OPTIONS made from a JavaScript frontend, using Axios, to the root level domain (e.g. https://domain.ddev.site) fail with a CORS 405 OPTIONS not allowed error, despite all OPTIONS requests to paths working fine.

Q: You can't be allowing the OPTIONS request then

That's just it, I am. All pathed requests work fine (i.e. https://domain.ddev.site/path). When making a request to the domain root, Axios throws the 405 for options but the request never reaches the index.php file. We see the access request in the nginx access.log

Q: Any other info?

Axios version: "axios": "^0.21.1",

We're stuck with Node 16 for now (no, thats not going to change).
Testing with ddev and Xdebug to watch the requests
Nothing in logs
Console throws CORS:

Access to XMLHttpRequest at 'https://domain.ddev.site/' from origin 'http://domain.ddev.site:8080' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource.

Appears to maybe be an nginx issue.

Solution

The issue it turns out is specific to the nginx configuration being used with DDev.

the inclution of the $uri/ element in the location try_files configuration results in a failier to correctly route OPTIONS requests made to the base domain onwards to the application.

As it turns out, $uri/ is in general not required for most modern web applications due to the almost ubiquitous use of a single exposed index file to handle all requests made to an application. As such, it can be safely removed, resolving the issue.

See Discussion here: https://github.com/serversideup/docker-php/issues/89

The specific fix is simple.

In the .ddev/nginx_full/nginx-site.conf file change:

location / {
    absolute_redirect off;
    try_files $uri $uri/ /index.php?$query_string;
}

location / {
    absolute_redirect off;
    try_files $uri /index.php?$query_string;
}

You will also need to remove the ##ddev generated comment at the top of the file to prevent the file being overwritten again.

Then restart ddev

ddev restart

and that should solve the issue.