How to set X-Script-Name header for virtual path?

[bjoernwuest]

I have the following compose file:

services:
  nginx-proxy:
    image: nginxproxy/nginx-proxy:alpine
    labels:
      - "com.github.jrcs.letsencrypt_nginx_proxy_companion.nginx_proxy"
    restart: always
    environment:
      - DEFAULT_ROOT: 301 https://some.where
      - TRUST_DOWNSTREAM_PROXY=false
    ports:
      - "80:80"
      - "443:443"
    volumes:
      - /var/run/docker.sock:/tmp/docker.sock:ro
      - acme_certs:/etc/nginx/certs
      - nginx_vhost:/etc/nginx/vhost.d
      - nginx_html:/usr/share/nginx/html
      - ./htpasswd:/etc/nginx/htpasswd

  postgres:
    image: postgres:15-alpine
    restart: always
    environment:
      - LANG=en_US.utf8
      - POSTGRES_USER=root
      - POSTGRES_PASSWORD=secret
      - POSTGRES_INITDB_ARGS=--locale-provider=icu --icu-locale=en-US
    volumes:
      - ./../no_backup/postgresql_data/fast:/var/lib/postgresql/data
      - ./../no_backup/postgresql_data/slow:/slowdata
      - ./init.sql:/docker-entrypoint-initdb.d/init.sql:ro
    expose:
      - "5432"
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -h localhost -p 5432 -t 5"]
      interval: 10s
      timeout: 5s
      retries: 12

  pgadmin:
    image: dpage/pgadmin4
    restart: always
    environment:
      - PGADMIN_DEFAULT_EMAIL=me@mail.post
      - PGADMIN_DEFAULT_PASSWORD=another_secret
      - VIRTUAL_PROTO=http
      - VIRTUAL_HOST=my.domain
      - VIRTUAL_PORT=80
      - VIRTUAL_PATH=/pgadmin
      - LETSENCRYPT_HOST=my.domain
    expose:
      - "80"
    depends_on:
      postgres:
        condition: service_healthy

volumes:
  acme_certs:
  nginx_vhost:
  nginx_html:

networks:
  default:
    external: true
    name: nginx-proxy

When invoking the pgadmin (http://my.domain/pgadmin) I get a http-404. The pgadmin page says that if it is reverse proxied to a virtual path, the proxy shall add proxy_set_header X-Script-Name /pgadmin . See here, in section HTTP via Nginx: https://www.pgadmin.org/docs/pgadmin4/latest/container_deployment.html

How to set this header just for this path? I prefer a solution that does not introduce another file that would be mounted into the nginx proxy, since part of the overall setup is the appealing fact that you can have anything in just one file.

[SchoNie]

I think the only solution, which does not introduce another file which would need to be mounted, is to use a subdomain instead of a subfolder.

If you really need a subfolder there is no other way then to include a custom location overrride to include that header
You already have nginx_vhost:/etc/nginx/vhost.d in your compose setup, so you just need to create 1 file.