id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	uname	nginx_version
1498	Named and capture variables cannot be used together	tiandrey@…		"Say I want to rewrite URI differently depending on something like client cookie. So I create a map (remembering that if is evil): 
{{{
map $cookie_foo $my_var {
    1 bar;
    default baz;
}
}}}
And later I try to do the obvious rewrite:
{{{
location / {
    rewrite ^/(.*) /$my_var/$1 break;
    proxy_pass http://backend;
}
}}}
... and it's tricky. In my case, if map returns default value (`baz`), everything works as planned. But if map returns non-default value (`bar`), `$1` in rewrite expands to empty string no matter what URI really is.

More over, this magic happens not only in `rewrite`, but in `set` too, for example, I tried the following:
{{{
if ( $uri ~ ^/(.*) ) {
    set $rewrite_path $my_var/$1;
    rewrite /.* /$rewrite_path break;
}
}}}
That doesn't work either. But the next piece of code finally works fine for me:
{{{
if ( $uri ~ ^/(.*) ) {
    set $tmp_var $1;
    rewrite /.* /$my_var/$tmp_var break;
}
}}}
But it's ugly AF.

Can you please fix it so that the original version (`rewrite ^/(.*) /$my_var/$1 break;`) works? Or please tell me what part of the documentation describes why this is impossible (but nevertheless works in some cases).


Debug log for both cases:
1) when map returns default value:
{{{
2018/03/02 19:25:09 [debug] 23380#0: *495 http map: ""0"" ""baz""
2018/03/02 19:25:09 [debug] 23380#0: *495 http script copy: ""/""
2018/03/02 19:25:09 [debug] 23380#0: *495 http script var: ""baz""
2018/03/02 19:25:09 [debug] 23380#0: *495 http script copy: ""/""
2018/03/02 19:25:09 [debug] 23380#0: *495 http script capture: ""mstatic/build/main.bundle.js""
2018/03/02 19:25:09 [debug] 23380#0: *495 http script regex end
2018/03/02 19:25:09 [notice] 23380#0: *495 rewritten data: ""/baz/mstatic/build/main.bundle.js""
}}}
URI is captured and capture variable is expanded all right - works as expected
2) when map returns non-default value:
{{{
2018/03/02 19:23:20 [debug] 23371#0: *74 http map: ""1"" ""bar""
2018/03/02 19:23:20 [debug] 23371#0: *74 http script copy: ""/""
2018/03/02 19:23:20 [debug] 23371#0: *74 http script var: ""bar""
2018/03/02 19:23:20 [debug] 23371#0: *74 http script copy: ""/""
2018/03/02 19:23:20 [debug] 23371#0: *74 http script capture: """"
2018/03/02 19:23:20 [debug] 23371#0: *74 http script regex end
2018/03/02 19:23:20 [notice] 23371#0: *74 rewritten data: ""/bar/""
}}}
URI was the same, but it says that capture is empty, so somebody is lying here."	defect	closed	minor		nginx-module	1.12.x	duplicate	if set rewrite variable		Linux servername 4.9.0-5-amd64 #1 SMP Debian 4.9.65-3+deb9u2 (2018-01-04) x86_64 GNU/Linux	"nginx version: nginx/1.12.1
built by gcc 4.9.2 (Debian 4.9.2-10) 
built with OpenSSL 1.0.2j  26 Sep 2016
TLS SNI support enabled
configure arguments: --prefix=/etc/nginx --sbin-path=/usr/sbin/nginx --conf-path=/etc/nginx/nginx.conf --error-log-path=/var/log/nginx/error.log --http-log-path=/var/log/nginx/access.log --pid-path=/run/nginx.pid --lock-path=/run/lock/nginx.lock --http-client-body-temp-path=/run/shm/body_temp --http-proxy-temp-path=/run/shm/proxy_temp --http-fastcgi-temp-path=/run/shm/fastcgi_temp --http-uwsgi-temp-path=/run/shm/uwsgi_temp --http-scgi-temp-path=/run/shm/scgi_temp --with-http_ssl_module --with-http_realip_module --with-http_sub_module --with-http_dav_module --with-http_gunzip_module --with-http_gzip_static_module --with-http_stub_status_module --with-mail --with-http_v2_module --with-http_geoip_module --with-select_module --with-http_auth_request_module --with-poll_module --with-debug"