@marianmeres/sveltekit-adapter-demino

A SvelteKit adapter that outputs a Web-standard handler(req, info) function compatible with @marianmeres/demino and any Deno.ServeHandler-based server.

Install

Install the adapter as an npm dev dependency in your SvelteKit project:

npm install -D @marianmeres/sveltekit-adapter-demino

The adapter runs at build time inside Vite/Node.js. It is not installed via deno add — Deno only runs the generated handler.js at serve time.

Configure

// svelte.config.js
import adapter from '@marianmeres/sveltekit-adapter-demino';

export default {
  kit: {
    adapter: adapter({
      out: 'build', // default
      // Cache-Control headers for disk-served static responses.
      // All values below are defaults — override or set to `false` to disable.
      cacheControl: {
        immutable:   'public, immutable, max-age=31536000',          // /_app/immutable/*
        prerendered: 'public, max-age=600, stale-while-revalidate=86400', // prerendered pages
        assets:      'public, max-age=86400',                        // unhashed static files
      },
    }),
  },
};

Note: SSR responses are not affected by these settings — use SvelteKit's handle hook in hooks.server.ts to control caching for server-rendered routes.

Build

vite build

Output structure:

build/
├── handler.js      <- import this in your Deno server
├── client/         <- static assets + prerendered HTML (served automatically)
└── server/         <- SvelteKit SSR runtime (used internally by handler.js)

Usage in your Deno server

import { demino, deminoCompose } from 'jsr:@marianmeres/demino';
import { handler as skHandler } from './build/handler.js';

const api = demino('/api');
api.get('/hello', () => ({ hello: 'world' }));

// SvelteKit handles everything that the API doesn't
const sk = demino();
sk.all('/*', skHandler);

Deno.serve(deminoCompose([api, sk]));

Or if SvelteKit is your only app:

import { handler } from './build/handler.js';
Deno.serve(handler);

How it works

The generated handler.js:

1. Prerendered redirects -- handles trailing-slash normalization (308 redirects) for prerendered pages, based on your SvelteKit trailingSlash config.

2. Static files & prerendered HTML -- served from build/client/ using @std/http/file-server's serveDir. This covers everything in your static/ folder, compiled JS/CSS (/_app/...), and prerendered pages. Each response gets a Cache-Control header based on its category:

   Category	Path pattern	Default header
   Immutable	/_app/immutable/*	public, immutable, max-age=31536000
   Prerendered	Pages from SvelteKit's prerender list	public, max-age=600, stale-while-revalidate=86400
   Static assets	Everything else (favicon, fonts, images…)	public, max-age=86400

   Override any value via cacheControl in adapter options, or set to false to skip setting the header for that category.

3. Everything else -- forwarded to SvelteKit's SSR engine via server.respond(). This handles server routes, SSR pages, and API endpoints defined inside your SvelteKit app.

4. Asset reading -- the handler provides a read() function to SvelteKit's server, enabling import { read } from '$app/server' for runtime asset access.

Notes

• Deno permissions needed at runtime: --allow-net, --allow-read, --allow-env

• The platform object available in SvelteKit hooks/endpoints will contain { info: Deno.ServeHandlerInfo }, giving you access to remoteAddr etc.

• The adapter runs in Node.js at build time (it's a Vite plugin). The generated handler.js runs in Deno at serve time.

• Your Deno server needs an import map for the npm packages that SvelteKit's SSR bundle references at runtime. The adapter emits build/deno-imports.json listing every bare specifier it found, each pinned to the version installed in your node_modules. Point your deno.json at it:

  // deno.json
  {
    "importMap": "./build/deno-imports.json"
  }
  

  Or copy its imports block into your existing deno.json imports. The file is regenerated on every build and keys are sorted alphabetically, so diffs stay clean.

  Disable emission with adapter({ denoImports: false }), or refine via adapter({ denoImports: { versionPrefix: "exact", exclude: ["tailwind-merge"], extraSpecifiers: ["some-dynamic-pkg"] } }).

  Caveats:

  • Dynamic import(someVar) with a computed string is invisible to any static scanner — use extraSpecifiers to force-add those entries.
  • A package whose exports doesn't list a subpath the SSR bundle actually imports will still error at runtime; no import map can work around that.

  Minimal manual fallback if you skip the generated file entirely:

  { "imports": { "@sveltejs/kit": "npm:@sveltejs/kit@^2.0.0" } }
  

License

MIT