Config Function

[Crisfole]

Describe the problem

Much like vite, some configuration options for svelte kit are dependent on the mode you're running in. In particular the hostHeader which is rarely wanted when you're running locally (some docker-configs excepted). Currently we have to rely on environment variables which are OK, but less smooth a path than vite's strategy of accepting either a function or a config object.

Describe the proposed solution

I'd love for svelte to accept either a config object, or a function that receives some environment information and returns the config object. I brainlessly spent about an hour this morning confusing the Vite and svelte configurations and assuming I could use a function for both. The hour wasted was my fault, but it did reveal a feature that would be simple and nice.

Alternatives considered

Environment variables.

Importance

would make my life easier

Additional Information

No response

[vpanyushenko]

Today for something like hostHeader, you can do something like:

const config = {
    kit: {
        target: "#svelte",
        hostHeader: process.env.NODE_ENV !== "development" ? "x-forwarded-host" : "",
    }
}

export default config;

And by checking the process.env.NODE_ENV, I guess you could write a function that could return a custom config object.

const config = yourCustomFunction(process.env.NODE_ENV)

export default config;

[dominikg]

fyi: this RFC sveltejs/rfcs#59 describes a solution for svelte config with builtin function support.

[Rich-Harris]

Given that top-level await is a thing, do we need function support?

[bluwy]

Perhaps a function would make more sense if we implement #1258

[Crisfole]

@Rich-Harris valid question. I think the consistency across APIs would make it more usable, but I'm easily persuaded here. I think I'm just too old - forgot top level await was allowed.

[Rich-Harris]

Going to close this for the sake of tracker hygiene unless another use case presents itself