feat: allow to run preflight validation only

[dummdidumm]

That way you can e.g. run preflight on each keystroke and full validation only on blur

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[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-kit-14744-svelte.vercel.app/

[Rich-Harris]

maybe this, so it's explicitly linked to .preflight(...)?

Suggested change

	clientOnly?: boolean;
	preflightOnly?: boolean;

[sillvva]

What would this look like in practice?

<script>
import { form } from "$lib/remote/forms.remote.ts";
import { schema } from "$lib/schema";

function validate() {
  form.preflight(schema).validate({ preflightOnly: true }); // runs preflight schema
  form.validate(); // runs server schema
}
</script>

<form {...form}></form>

or

<script>
import { form } from "$lib/remote/forms.remote.ts";
import { schema } from "$lib/schema";

function validate() {
  form.validate(); // runs preflight schema
  form.validate({ preflightOnly: false }); // skips preflight, runs server schema
}
</script>

<form {...form.preflight(schema)}></form>

[Rich-Harris]

The preflight schema would always be used. This just allows you to skip server validation. So you could for example do preflight validation on every keystroke, but additionally run server validation on change events (which are emitted when you blur an input you've been typing into, etc):

<form
  {...myform.preflight(schema)}
  oninput={() => myform.validate({ preflightOnly: true })}
  onchange={() => myform.validate()}
>...</form>