Hello,
I noticed that config:

server {
location / {
// doesn't exist, will result in 502
proxy_pass http://localhost:11111;
error_page 502 @fetch;
}
location @fetch {
proxy_pass http://localhost:8080;
}
}

will result in response from http://localhost:8080 and "502 Bad Gateway"
status,
while config:

server {
location / {
// doesn't exist, will result in 502
proxy_pass http://localhost:11111;
error_page 502 = @fetch;
}
location @fetch {
proxy_pass http://localhost:8080;
}
}

will result in response from http://localhost:8080 and "200 OK" status.

The cause of this difference is '=' sign and the fact that
ngx_http_core_error_page function sets overwrite to -1 in first case, and
overwrite to 0 in second case.

Is passing original response status with headers and body from "error page"
some kind of feature or is it a bug and error pages without '=' shouldn't be
allowed at all?

Best regards,
Piotr Sikora < piotr.sikora@frickle.com >