nginx PATH_INFO issue - leading / missing

[bobtfish]

From the PSGI spec: PATH_INFO If this key is not empty, it MUST start with a forward slash (/).

I'm seeing PATH_INFO like 'public' instead of '/public', with nginx 0.7.59

This happens with BOTH of:
fastcgi_param PATH_INFO $fastcgi_script_name;
fastcgi_param PATH_INFO /$fastcgi_script_name;

In my nginx config. And so appears to be something I can't control / fix.

Should there be a middleware to detect/correct this for specific nginx releases (I don't know which ones yet...), or is it a generic enough fix (just prepending the slash if not present and non-empty) to just add to the FCGI handler?

Thoughts welcome about the best way to fix this - I'm happy to work up test cases and a patch once I've got your opinion about where would be best to patch.

[bobtfish]

For reference, I've applied this middleware locally in the app which was causing my troubles:

https://gist.github.com/2429475

and the problem I had (URLMap not matching) is fixed, as would be expected.

[miyagawa]

Can you try with other, possibly newer versions of nginx to see if it's related?

[miyagawa]

Here's the relevant snippet from the docs: note that none of them uses nginx-provided FCGI params for script_name or path_info since it's known to be incorrect.

      location / {
        set $script "";
        set $path_info $uri;
        fastcgi_pass unix:/tmp/fastcgi.sock;
        fastcgi_param  SCRIPT_NAME      $script;
        fastcgi_param  PATH_INFO        $path_info;