Automatically disable +layout.server.ts and server.ts for static sites

Describe the bug

I'm writing on code base to rule them all (Capacitor SPA (iOS + Android) & Web SSR)

I do the following in the config

import { vitePreprocess } from "@sveltejs/vite-plugin-svelte";
import adapterNode from "@sveltejs/adapter-node";
import adapterStatic from "@sveltejs/adapter-static";

// Determine the mode - this can be set as an environment variable or changed manually
const BUILD_MODE = process.env.BUILD_MODE || "SSR"; // default to SSR, change to 'SPA' for SPA mode

let adapterOptions = {};

// Switch depending on the mode
if (BUILD_MODE === "SPA") {
    adapterOptions = {
        pages: "build_spa",
        assets: "build_spa",
        strict: true,
        fallback: "index.html",
    };
} else {
    adapterOptions = {
        pages: "target/classes/static/",
        assets: "target/classes/static/",
        fallback: "index.html",
    };
}

const adapter = BUILD_MODE === "SSR" ? adapterNode(adapterOptions) : adapterStatic(adapterOptions);

/** @type {import('@sveltejs/kit').Config} */
const config = {
    // Consult https://kit.svelte.dev/docs/integrations#preprocessors
    // for more information about preprocessors
    preprocess: vitePreprocess(),

    kit: {
        adapter,
    },
};

export default config;

When I build the app for capacitor I have to manually rename the +server.layout files, then name them back safely.

#!/bin/bash

# Build the SvelteKit app for Mobile (SPA)

# Function to rename +layout.server.ts files to +layout.server.ts.bak
rename_layout_files() {
    find $SRC_DIR -type f -name "+layout.server.ts" -exec mv {} {}.bak \;
}

# Function to rename +layout.server.ts.bak files back to +layout.server.ts
restore_layout_files() {
    find $SRC_DIR -type f -name "+layout.server.ts.bak" -exec sh -c 'mv "$0" "${0%.bak}"' {} \;
}

# Trap to ensure that restore_layout_files is called if the script exits early due to an error
trap 'restore_layout_files' EXIT

# Abort on any error (including if find or npm run fails)
set -e

# Set env
export PUBLIC_DEV=TRUE
export BUILD_MODE=SPA

SRC_DIR="./src"

# Rename +layout.server.ts files before the build
rename_layout_files

vite build --mode production --base

# Rename +layout.server.ts files back after successful build
# The restore_layout_files function will also be called here due to the trap if the script hasn't exited early
restore_layout_files

npx cap sync
# npx cap open ios
# npx cap open android

# Clear the trap
trap - EXIT
 

It would be nice if there was some config to do this automatically and it would also be nice to have __data.json explained in the docs.

Reproduction

It's mentioned in the description.

Logs

No response

System Info

System:
    OS: macOS 14.3.1
    CPU: (8) arm64 Apple M1 Pro
    Memory: 333.03 MB / 16.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 21.6.2 - /opt/homebrew/bin/node
    npm: 10.2.4 - /opt/homebrew/bin/npm
    pnpm: 8.6.12 - ~/Library/pnpm/pnpm
  Browsers:
    Chrome: 120.0.6099.71
    Safari: 17.3.1

Severity

annoyance

Start with the SvelteKit config that switches between adapterNode and adapterStatic, then trace how +layout.server.ts and +server.ts are handled during static builds. Define what static mode should disable, verify the Capacitor build without renaming files, and explain __data.json in the documentation.