Unable to load static UI files

Q&A (please complete the following information)

• OS: 5.7.9-1-MANJARO
• Browser: firefox
• Version: 78
• Method of installation: docker
• Swagger-UI version: 3.30.0
• Swagger/OpenAPI version: OpenAPI 3.0

Content & configuration

Running docker-compose with swagger and nginx, consider the following docker-compose.yml:

version: '3'

services:
  swagger:
    image: swaggerapi/swagger-ui:v3.30.0
    ...
  nginx:
    image: nginx:mainline-alpine
    depends_on:
      - swagger
    ports:
      - 80:80
    volumes:
      - ./nginx.conf:/etc/nginx/nginx.conf

and the following nginx.conf:

http {
  server {
    listen 80 default_server;
    server_name _;
    location /swagger {
      proxy_pass http://swagger:8080/;
    }
  }
}

Describe the bug you're encountering

When going to http://localhost the html loads fine however the static assets linked from the html don't seem to load. When looking in the network inspector I noticed that the assets are loaded from localhost/<FILE_NAME> instead of localhost/docs/<FILE_NAME>.

One of the outgoing requests to an asset:

GET /swagger-ui.css HTTP/1.1
Host: localhost
User-Agent: Mozilla [REDACTED]
Accept: text/css,*/*;q=0.1
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
DNT: 1
Connection: keep-alive
Referer: http://localhost/swagger
Cache-Control: max-age=0

and the response:

HTTP/1.1 404 Not Found
Server: nginx
Date: Tue, 21 Jul 2020 07:45:18 GMT
Content-Type: text/html; charset=utf-8
Content-Length: 2439
Connection: keep-alive
Cache-Control: no-store, must-revalidate
ETag: "987-pkNlMUTYJp6pkXv/jlWCJfwNiNM"

To reproduce...

Steps to reproduce the behavior:

1. Create a local directory with the files described in Content & configuration.
2. Run docker-compose up.
3. Go to http://localhost/docs
4. Confirm that static assets are not being loaded.

Expected behavior

The files are referred from the base URL and thus properly loaded.

Additional context or thoughts

I also tried to set the BASE_URL environmental variable to /swagger and changed the nginx proxy_pass to http://swagger:8080/docs/ however it yielded the same result.

Start with the nginx.conf and docker-compose.yml configuration shown in the issue, then reproduce the missing static assets through the /swagger path. Trace how Swagger UI generates its asset URLs and compare them with the proxy path. Done means the HTML and static files load correctly when accessed through the configured path.