fix(nginx): custom locations take precedence over Cache Assets regex (location ^~)

[pos-ei-don]

Problem

A proxy host with a Custom Location pointing at a different upstream (e.g. /paperless -> a Paperless container) and Cache Assets enabled returns 404 for static files under that path (/paperless/static/app.js, .css, ...). The Custom Location's HTML/API paths work; only asset extensions break.

Root cause

Cache Assets includes a server-level regex location location ~* \.(css|js|png|...)$ { proxy_pass <main upstream>; }. In nginx, regex locations take precedence over prefix locations, so this regex beats the Custom Location location {{ path }} (plain prefix) generated by _location.conf. Asset requests under custom paths are routed to the main upstream (which doesn't know them) -> 404. The UI offers no way to raise the custom location's priority.

Related: #2557, #1981, #4423.

Change

Emit custom locations as location ^~ {{ path }}. ^~ gives the prefix location precedence over regex locations, so the cached-asset regex no longer hijacks custom-location paths.

Caveat

^~ disables regex matching within that path. Users who intend a Custom Location path as a regex would be affected. If custom paths may be regex, a guarded variant (only ^~ for plain prefixes) would be safer — happy to adjust based on maintainer preference.

Test

1. Proxy host example -> upstream A; Custom Location /sub -> upstream B serving /sub/x.js.
2. Enable Cache Assets -> /sub/x.js = 404 (bug).
3. With this change -> /sub/x.js = 200 from B; main-upstream assets still cached.

[nginxproxymanagerci]

Docker Image for build 1 is available on DockerHub:

nginxproxymanager/nginx-proxy-manager-dev:pr-5697

Note

Ensure you backup your NPM instance before testing this image! Especially if there are database changes.
This is a different docker image namespace than the official image.

Warning

Changes and additions to DNS Providers require verification by at least 2 members of the community!