How to handle relative urls correctly with a nginx reverse proxy

The problem is basically that using a proxy_pass directive won't rewrite HTML code and therefor relative URL's to for instance a img src="/assets/image.png" won't magically change to img src="/bbb/assets/image.png".

I wrote about potential strategies to address that in Apache httpd here and similar solutions are possible for nginx as well:

• If you have control over example.com and the how the application/content is deployed there, deploy in the same base URI you want to use on example.net for the reverse proxy
  --> deploy your code in example.com/bbb and then your proxy_pass will become quite an easy as /assets/image.png will have been moved to /bbb/assets/image.png:

  location /bbb/ {
       proxy_pass http://example.com/bbb/; 
  

• If you have control over example.com and the how the application/content is deployed:
  change to relative paths, i.e. rather than img src="/assets/image.png"
  refer to img src="./assets/image.png" from a page example.com/index.html
  and to img src="../../assets/image.png"from a page example.com/some/path/index.html

• Maybe you're lucky and example.com only uses a few URI paths in the root and non of those are used by example.net, then simply reverse proxy every necessary subdirectory:

  location /bbb/ {
       proxy_pass http://example.com/; 
  }
  location /assets/ {
       proxy_pass http://example.com/assets/; 
  }
  location /styles/ {
       proxy_pass http://example.com/styles/; 
  

• give up using a example.com as subdirectory on example.net and instead host it on a subdomain of example.net:

  server { 
    server_name bbb.example.net 
    location / {
       proxy_pass http://example.com/; 
    }
  }
  

• rewrite the (HTML) content by enabling the nginx ngx_http_sub_module. That will also allow you to rewrite absolute URL's with something similar to:

  location /bbb/ {
       sub_filter 'src="/assets/'  'src="/bbb/assets/';
       sub_filter 'src="http://example.com/js/' 'src="http://www.example.net/bbb/js/' ;
       sub_filter_once off;
       proxy_pass http://example.com/; 
  }