adapter-static `fallback` page not generated when `prerender.enabled` is `false`

Describe the bug Using the adapter static in “SPA” configuration doesn’t output any html entry point even though the build completes without errors. All other bundled assets are created as far as i can tell. /build contains

/_app
  |--/assets
  |--/chunks
  |--/pages
  |--...misc.js
_redirects

Logs Build completes successfully with logs ending in

vite v2.3.3 building SSR bundle for production...
✓ 38 modules transformed.
.svelte-kit/output/server/app.js   396.41kb

Run npm run preview to preview your production build locally.

> Using @sveltejs/adapter-static
  ✔ done
✨  Done in 3.72s.

To Reproduce svelte.config.js

import preprocess from 'svelte-preprocess';
import adapter from '@sveltejs/adapter-static';

/** @type {import('@sveltejs/kit').Config} */
const config = {
  // Consult https://github.com/sveltejs/svelte-preprocess
  // for more information about preprocessors
  preprocess: preprocess(),
  kit: {
    // hydrate the <div id="svelte"> element in src/app.html
    target: '#svelte',
    adapter: adapter({
      fallback: "index.html"
    }),
    prerender: {
      enabled: false
    },
    ssr: false,
    vite: {
      ssr: {
        noExternal: ["chart.js"]
      },
    }
  }
};

export default config;

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Expected behavior Entrypoint index html should be generated in the root of the build dir

Stacktraces N/A

Information about your SvelteKit Installation:

Diagnostics

System: OS: macOS 11.1 CPU: (8) arm64 Apple M1 Memory: 520.03 MB / 16.00 GB Shell: 5.8 - /bin/zsh Binaries: Node: 16.1.0 - ~/.nvm/versions/node/v16.1.0/bin/node Yarn: 1.22.10 - /opt/homebrew/bin/yarn npm: 7.11.2 - ~/.nvm/versions/node/v16.1.0/bin/npm Browsers: Brave Browser: 91.1.25.68 Firefox: 88.0.1 Safari: 14.0.2 npmPackages: @sveltejs/kit: ^1.0.0-next.110 => 1.0.0-next.110 svelte: ^3.34.0 => 3.38.2

• Adapter-Static

Severity How severe an issue is this bug to you? Is this annoying, blocking some users, blocking an upgrade or blocking your usage of SvelteKit entirely?

This is medium high severity, we are unable to deploy our svelte kit SPA, although the dev server works fine

[harvey-k]

@benmccann Adding the following to packages\adapter-static\test\apps\spa\svelte.config.js reproduces this issue.

  prerender: {
    enabled: false
  },
  ssr: false,

PR #2128 makes the tests pass again.

Would the above config changes make a more representative “spa mode” test or would you prefer an separate test app from prerendered and spa be created?

[benmccann]

Can anyone provide a repo that reproduces this issue?