[PATCH] implement a $location variable

[Maxim Dounin]

Hello!

On Mon, Oct 15, 2012 at 11:22:00AM +1000, David Gwynne wrote:

> this patch is actually from piotr sikora, and is part of coolkit 
> already. this is just a port of it to stock nginx.
> 
> this makes the part of the request uri that matches the 
> locations name available as a variable within a block. eg if you 
> have location /foo { } and request /foo/bar/foo, $location will 
> have the value /foo. if you have location ^~ /(foo|bar) and 
> request /foo/bar/foo, $location will still have /foo in it. 
> think of it as $0 for regex locations, but it works for 
> non-regex location names too.
> 
> im running this in production now and its working great. it 
> allows me to treat the locations name as a parameter to an 
> applications front end controller without having to repeat the 
> value within a location block.

Behaviour within regexp locations is counterintuitive, and 
contradicts to what the variable does in a normal location.

> --- src/http/ngx_http_variables.c.orig  Tue Jul  3 03:41:52 2012
> +++ src/http/ngx_http_variables.c       Thu Aug 23 10:32:22 2012
> @@ -65,6 +65,8 @@ static ngx_int_t ngx_http_variable_request_filename(ng
>   ngx_http_variable_value_t *v, uintptr_t data);
> static ngx_int_t ngx_http_variable_server_name(ngx_http_request_t *r,
>   ngx_http_variable_value_t *v, uintptr_t data);
> +static ngx_int_t ngx_http_variable_location(ngx_http_request_t *r,
> +    ngx_http_variable_value_t *v, uintptr_t data);

Just a side note: your mail client corrupts patches.

[...]

> +    if (clcf->regex) {
> +        rc = ngx_regex_exec(clcf->regex->regex, &r->uri, captures, 3);
> +
> +        if (rc == NGX_REGEX_NO_MATCHED) {
> +            return NGX_ERROR;
> +        }
> +
> +        v->data = r->uri.data + captures[0];
> +        v->len = captures[1] - captures[0];

Note that result is actually unstable in the regexp location case, 
as the code re-executes regular expression against a possibly 
changed URI.

[...]

-- 
Maxim Dounin
http://nginx.com/support.html