Nginx - Localhost port is lost when clicking on anchor links - docker

Question

I'm using Docker to run nginx on macOS to serve static files on http://localhost:8080.
When clicking on an anchor link, the port is being lost.
For example, clicking on <a href="/foo"> will link to http://localhost/foo instead of http://localhost:8080/foo.
My nginx config is:
server {
listen 80 default_server;
server_name _;
root /var/www/root;
index index.html index.php;
location ~ /\. {
deny all;
}
location ~* /(?:uploads|files)/.*\.php$ {
deny all;
}
error_page 404 /404.html;
location / {
try_files $uri $uri/ $uri.html =404;
}
location ~ \.php$ {
include /etc/nginx/fastcgi_params;
fastcgi_pass php:9000;
fastcgi_index index.php;
fastcgi_param SCRIPT_FILENAME $document_root/$fastcgi_script_name;
}
}
The directory structure of /var/www/root is:
├── foo
│   └── index.html
├── bar
│   └── index.html
└── baz
└── index.html
However, when changing:
try_files $uri $uri/ $uri.html =404;
to:
try_files $uri/index.html $uri $uri/ $uri.html =404;
the anchor links link correctly.
However, the following does not work:
try_files $uri/ $uri $uri.html =404;
What is going on exactly? Is there a way to exclude $uri/index.html from try_files and have the anchor links preserve the port?
Update
This works, but I'm not quite sure why.
if (-d $request_filename) {
rewrite [^/]$ $scheme://$http_host$uri/ permanent;
}
location / {
try_files $uri $uri/ $uri.html =404;
}

Answer 1

I can't see the Dockerfile but I'm assuming you run the container with a port mapping of 8080:80. However, nginx is probably still sending the Host header with port 80 and the anchor tag uses that host given how the base URI is calculated:
User agents must calculate the base URI according to the following precedences (highest priority to lowest):
The base URI is set by the BASE element.
The base URI is given by meta data discovered during a protocol interaction, such as an HTTP header (see [RFC2616]).
By default, the base URI is that of the current document. Not all HTML documents have a base URI (e.g., a valid HTML document may appear in an email and may not be designated by a URI). Such HTML documents are considered erroneous if they contain relative URIs and rely on a default base URI.
Reference: https://www.w3.org/TR/html401/struct/links.html#edef-BASE
For development, it sounds like running the container with 8080:8080 should work. For production you might wanna set the appropriate server_name or Host header via an envvar.