Component context is not initialized when rendering server components

[oettingerj]

Describe the bug

I have a Svelte component in Repo A, with a Vite server configured to emit code for the server:

svelte({
	dynamicCompileOptions() {
		return { generate: 'server' }
	}
})

I'm using dynamicCompileOptions here because generate is not typically configurable within the svelte Vite plugin, and the only other way I'm aware of to trigger the compilation of SSR code is to use ssrLoadModule, which doesn't fit my use case.

Repo A exports an index.js file with render() and mount() functions.
Repo B is a SvelteKit site, which dynamically imports the module from Repo A over http using an import hook.

So far so good. However, when I call render() within the SvelteKit site, I get lifecycle_outside_component errors any time I try to set/get context or call onMount during component initialization. Digging further, it seems set_component_context is not called before rendering, resulting in component_context being null within internal/client/context.js.

Notwithstanding how nonstandard this architecture is, I'd expect onMount and set/getContext to work properly.

Reproduction

REPO

Logs

System Info

System:
    OS: macOS 15.3.1
    CPU: (16) arm64 Apple M4 Max
    Memory: 3.87 GB / 64.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 23.4.0 - ~/.local/share/mise/installs/node/23.4.0/bin/node
    npm: 10.9.2 - ~/.local/share/mise/installs/node/23.4.0/bin/npm
  Browsers:
    Safari: 18.3
  npmPackages:
    svelte: ^5.0.0 => 5.23.0

Severity

annoyance

[paoloricciuti]

This is a bit of a weird setup...the problem you are facing is that you are generating a server svelte component...this is meant to be used in server runtimes where onMount is actually a noop. However with your setup you are generating the server code but you are accessing with an http request so the import { onMount } from 'svelte'; is resolved by vite to the browser version which can't work with the server version of the component.

What are you trying to actually achieve here?

[oettingerj]

Makes sense. I'm working on a micro-frontend architecture in which one repo exports components to be loaded dynamically for SSR by a separate SvelteKit server. I eventually realized this was not the direction to go, and am now blocked by #13186 instead. This can be closed.