give an option for default host and port when building with `adapter-node`

Describe the problem

when building an app using adapter-node i would like to be able to choose the default port and host

right now if i run $ svelte-kit build it automatically chooses "0.0.0.0" as the default host and 3000 as the default port and would like to be able to control that (for the build)

the only way that i could find to change the host and port is using

$ HOST=localhost PORT=4000 node build

to start the app, but that is temporary and only affects the environmental variables and not the defaults and i would have to do that every time i start

if there is a way to specify that and i haven’t found it then i’m sorry, if this is a duplicate then i am too.

iirc there used to be a time where you could specify the --port [port] option as you ran $ svelte-kit build but i don’t know if that actually did anything or if i even remember correctly

Describe the proposed solution

config

i would suggest adding the option default (or maybe defaults, given that it is port and host), so the config could look something like this

import node from "adapter-node"

export default {
    kit: {
        adapter: node({
            default: {
                host: "localhost",
                port: 4000
            }
        })
    }
}

implementation

i dont really know a lot about this codebase so i dont actually know how one would implement that but in the adapter-node index.js file, lines 58 through 63, where it goes

writeFileSync(
    '.svelte-kit/node/env.js',
    `export const host = process.env[${JSON.stringify(
        host_env
    )}] || '0.0.0.0';\nexport const port = process.env[${JSON.stringify(port_env)}] || 3000;`
);

seems like an idea and then after line 37 you could add a line with

    default: { host: default_host = '0.0.0.0', port: default_port = 3000 } = {},

~but i don’t know if that would work~

after a bit of testing, adding that line and expanding the first-mentioned code to

writeFileSync(
    '.svelte-kit/node/env.js',
    `export const host = process.env[${JSON.stringify(
        host_env
    )}] || ${JSON.stringify(default_host)};\nexport const port = process.env[${JSON.stringify(
        port_env
    )}] || ${JSON.stringify(default_port)};`
);

works as expected, a very simple fix to a very simple problem, i would just need some confirmation on whether or not this would be a good addition by the package-maintainers

Alternatives considered

like i already mentioned the only alternative i found is to start your production server with

$ HOST=localhost PORT=4000 node build

but i find that tedious and would appreciate if i could just give standard options to the builder

Importance

nice to have

Additional Information

no additional information

[sridharraman]

@xpat I have a similar issue. I am trying to host multiple sveltekit apps in my server. I have an added requirement that the apps run by pm2 are in specific locations. If I use location /, I am able to view the app in the browser. But if I use any another location in my nginx config, it doesn’t work. Do you face that issue too?

[cbergen]

This looks like is the same trap I fell into. The svelte.config.js env variables are not intended for setting server environment variable values. They tell svelte which env variable names to use. So in svelte.config.js,

The default is:

// svelte.config.js
import adapter from '@sveltejs/adapter-node';

export default {
	kit: {
		adapter: adapter({
			// default options are shown
			out: 'build',
			precompress: false,
			env: {
				host: 'HOST',
				port: 'PORT'
			}
		})
	}
};

The above tells svelte to look for the env variable HOST and PORT. These must be strings and on your server in your .env or whatever you would use HOST=localhost PORT=4000

The only time you would need to change the svelte.config.js env settings is in a case like this:

// svelte.config.js
import adapter from '@sveltejs/adapter-node';

export default {
	kit: {
		adapter: adapter({
			out: 'build',
			precompress: false,
			env: {
				host: 'MYHOST',
				port: 'MYPORT'
			}
		})
	}
};

And then starting the node server like:

MYHOST=localhost MYPORT=4000 node build

Basically the server determines the port, adapter-node can work on whatever port it needs as long as it knows what environment variables to look for.