Fix type check for link options

[hyunbinseo]

Describe the bug

I am not sure if this is the right repo. Please move if incorrect.

SvelteKit link options do not show type errors:

<!-- error in class attr. only -->
<div
  data-sveltekit-keepfocus={3}
  data-sveltekit-noscroll={3}
  data-sveltekit-preload-code={3}
  data-sveltekit-preload-data={3}
  data-sveltekit-reload={3}
  data-sveltekit-replacestate={3}
  class={3}
></div>

The type seems to live here in the Svelte repo:

https://github.com/sveltejs/svelte/blob/svelte%405.46.0/packages/svelte/elements.d.ts#L854-L869

'data-sveltekit-keepfocus'?: true | '' | 'off' | undefined | null;
'data-sveltekit-noscroll'?: true | '' | 'off' | undefined | null;
'data-sveltekit-preload-code'?:
  | true
  | ''
  | 'eager'
  | 'viewport'
  | 'hover'
  | 'tap'
  | 'off'
  | undefined
  | null;
'data-sveltekit-preload-data'?: true | '' | 'hover' | 'tap' | 'off' | undefined | null;
'data-sveltekit-reload'?: true | '' | 'off' | undefined | null;
'data-sveltekit-replacestate'?: true | '' | 'off' | undefined | null;

though it does exist in the SvelteKit repo as well:

kit/packages/kit/src/core/sync/write_non_ambient.js

Lines 16 to 45 in fe76722

	// `declare module "svelte/elements"` needs to happen in a non-ambient module, and dts-buddy generates one big ambient module,
	// so we can't add it there - therefore generate the typings ourselves here.
	// We're not using the `declare namespace svelteHTML` variant because that one doesn't augment the HTMLAttributes interface
	// people could use to type their own components.
	// The T generic is needed or else there's a "all declarations must have identical type parameters" error.
	const template = `
	${GENERATED_COMMENT}
	declare module "svelte/elements" {
	export interface HTMLAttributes<T> {
	'data-sveltekit-keepfocus'?: true | '' | 'off' | undefined | null;
	'data-sveltekit-noscroll'?: true | '' | 'off' | undefined | null;
	'data-sveltekit-preload-code'?:
	| true
	| ''
	| 'eager'
	| 'viewport'
	| 'hover'
	| 'tap'
	| 'off'
	| undefined
	| null;
	'data-sveltekit-preload-data'?: true | '' | 'hover' | 'tap' | 'off' | undefined | null;
	'data-sveltekit-reload'?: true | '' | 'off' | undefined | null;
	'data-sveltekit-replacestate'?: true | '' | 'off' | undefined | null;
	}
	}
	export {};
	`;

Note that false does seem to disable preload data. See #15064 (comment)

data-sveltekit-preload-data={false}
data-sveltekit-preload-data="off"

Reproduction

Reproducible on a new sv create template

Logs

System Info

System:
  OS: Windows 11 10.0.26200
  CPU: (8) x64 Intel(R) Core(TM) Ultra 7 258V
  Memory: 7.11 GB / 31.48 GB
Binaries:
  Node: 24.12.0 - C:\Users\hyunb\AppData\Local\fnm_multishells\3552_1765851436409\node.EXE
  Yarn: 1.22.22 - C:\Users\hyunb\AppData\Local\fnm_multishells\3552_1765851436409\yarn.CMD
  npm: 11.6.2 - C:\Users\hyunb\AppData\Local\fnm_multishells\3552_1765851436409\npm.CMD
  pnpm: 10.25.0 - C:\Users\hyunb\AppData\Local\fnm_multishells\3552_1765851436409\pnpm.CMD
  Deno: 2.4.0 - C:\Users\hyunb\.deno\bin\deno.EXE
Browsers:
  Chrome: 143.0.7499.110
  Edge: Chromium (140.0.3485.54)
  Firefox: 146.0 - C:\Program Files\Mozilla Firefox\firefox.exe

Severity

annoyance

[Rich-Harris]

We can't fix this in the types — see sveltejs/svelte#17598 (comment) — but we could probably add runtime validation instead. Transferring this to the kit repo