Expose `$env/static/public` module to service workers

[Rich-Harris]

Describe the problem

#5663 adds new modules with environment variables. In some cases it's useful to be able to access those env vars in a service worker.

It only makes sense to expose public environment variables for obvious reasons, so $env/static/private and $env/dynamic/private are out.

$env/dynamic/public could potentially be useful, but I have no idea how it would work. I think 'service workers can only use public environment variables that are known at build time' is a reasonable restriction.

Describe the proposed solution

Expose $env/static/public to service workers.

Alternatives considered

No response

Importance

nice to have

Additional Information

No response

[elliott-with-the-longest-name-on-github]

Rich, is it possible to expose dynamic vars to the service worker by sending a message to it containing the variables during the client initialization? If it happens then, it'd be guaranteed to preempt any messages sent by user code, right?

[Rich-Harris]

No, the service worker has to initialise before it's possible to send messages to it

[Chooks22]

I just ran into this issue while adding a check to ignore cache for requests going to our proxy, whose url is set using a static public env var

For now I could workaround with our project but would be nice to see this feature implemented for other cases where workarounds might not be possible 👍

[frederikhors]

This is REALLY NEEDED.

Today I updated to kit 1.0.3 coming from "@sveltejs/kit": "1.0.0-next.394" and the build is not replacing these anymore:

• service-worker.ts:

registerRoute(
  new NavigationRoute(createHandlerBoundToURL("/index.html"), {
    denylist: [new RegExp(import.meta.env.VITE_SOME_ENV + "/")],
  })
);

VITE_SOME_ENV is in .env file.

Why?

Is there a work-around until this issue is closed (done)?

UPDATE: I was wrong. This is working using the VITE_ prefix. Not the Kit's defualt one PUBLIC_.

I think I need to find a work-around for now.

[elliott-with-the-longest-name-on-github]

@frederikhors

You are correct -- we don't touch Vite's env var handling, so that's a good escape hatch until we get this working. Keep in mind that it doesn't have the public/private protections of Kit's env vars -- don't accidentally expose secrets! 😁

[kyllerss]

I just ran into this issue as well. +1 from me.