Add support for form arrays

src/lib/client/superForm.ts

@@ -389,6 +389,30 @@ try {
 	// No Storybook
 }
 
+const lifeCycleCallbacks = {
+	onDestroy: new Set<() => void>(),
+	beforeNavigate: new Set<(nav: BeforeNavigate) => Promise<void>>()
+}
+let componentInitialized = false;
+function initLifeCycleCallbacks() {
+	if (componentInitialized) return;
+	componentInitialized = true;
+
+	onDestroy(() => {
+		for (const callback of lifeCycleCallbacks.onDestroy) {
+			callback();
+		}
+		lifeCycleCallbacks.onDestroy.clear();
+	});
+
+	beforeNavigate((nav: BeforeNavigate) => {
+		for (const callback of lifeCycleCallbacks.beforeNavigate) {
+			callback(nav);
+		}
+		lifeCycleCallbacks.beforeNavigate.clear();
+	});
+}
+
 /////////////////////////////////////////////////////////////////////
 
 /**
@@ -410,6 +434,8 @@ export function superForm<
 	// To check if a full validator is used when switching options.validators dynamically
 	let initialValidator: FormOptions<T, M, In>['validators'] | undefined = undefined;
 
+	initLifeCycleCallbacks();
+
 	{
 		if (options.legacy ?? LEGACY_MODE) {
 			if (options.resetForm === undefined) options.resetForm = false;
@@ -465,7 +491,12 @@ export function superForm<
 		form = form as SuperValidated<T, M, In>;
 
 		// Assign options.id to form, if it exists
-		const _initialFormId = (form.id = options.id ?? form.id);
+		// Avoid reassigning id in runes mode to avoid ERR_SVELTE_UNSAFE_MUTATION
+		// TODO: detect runes mode if possible & warn if id is different
+		let _initialFormId = form.id
+		if (options.id && form.id !== options.id) {
+			_initialFormId = options.id;
+		}
 		const _currentPage = get(page) ?? (STORYBOOK_MODE ? {} : undefined);
 
 		// Check multiple id's
@@ -525,7 +556,7 @@ export function superForm<
 
 		///// From here, form is properly initialized /////
 
-		onDestroy(() => {
+		lifeCycleCallbacks.onDestroy.add(() => {
 			Unsubscriptions_unsubscribe();
 			NextChange_clear();
 			EnhancedForm_destroy();
@@ -1397,7 +1428,7 @@ export function superForm<
 	///// Store subscriptions ///////////////////////////////////////////////////
 
 	if (browser) {
-		beforeNavigate(Tainted_check);
+		lifeCycleCallbacks.beforeNavigate.add(Tainted_check);
 
 		// Need to subscribe to catch page invalidation.
 		Unsubscriptions_add(

src/routes/(v2)/v2/Navigation.svelte

@@ -14,6 +14,7 @@
 		'issue-337-checkboxes',
 		'issue-345',
 		'letters',
+		'multiple-forms',
 		'multiple-files',
 		'multistep-client',
 		'multistep-server',

src/routes/(v2)/v2/multiple-forms/+page.server.ts

@@ -0,0 +1,58 @@
+import { zod } from '$lib/adapters/zod.js';
+import { message, superValidate } from '$lib/server/index.js';
+import { type Actions, fail } from '@sveltejs/kit';
+import { schema } from './schema.js';
+
+const items = [
+	{
+		id: 1,
+		label: 'One'
+	},
+	{
+		id: 2,
+		label: 'Two'
+	},
+	{
+		id: 3,
+		label: 'Three'
+	}
+];
+
+export const load = async () => {
+	const item_forms = await Promise.all(
+		items.map((item) =>
+			superValidate(item, zod(schema), {
+				id: item.id.toString()
+			})
+		)
+	);
+
+	return { item_forms };
+};
+
+export const actions: Actions = {
+	async create() {
+		items.push({
+			id: items.length + 1,
+			label: (items.length + 1).toString()
+		});
+
+		return { success: true };
+	},
+
+	async save({ request }) {
+		const form = await superValidate(request, zod(schema));
+
+		if (!form.valid) {
+			// Again, return { form } and things will just work.
+			return fail(400, { form });
+		}
+
+		const index = items.findIndex((item) => item.id === form.data.id);
+		if(index !== -1) {
+			items[index].label = form.data.label;
+		}
+
+		return message(form, `Item ${form.data.id} updated`);
+	}
+};

src/routes/(v2)/v2/multiple-forms/+page.svelte

@@ -0,0 +1,27 @@
+<script lang="ts">
+	import type { PageData } from './$types.js';
+	import { superForm } from '$lib/client/index.js';
+	import Form from './Form.svelte';
+	import { enhance } from '$app/forms';
+	import { get } from 'svelte/store';
+
+	let {
+		data
+	}: {
+		data: PageData;
+	} = $props();
+
+	const superforms = $derived(data.item_forms.map(item_form => superForm(item_form, {
+		id: item_form.id,
+		dataType: 'json'
+	})));
+</script>
+
+{#each superforms as superform (get(superform.formId))}
+	<Form {superform} />
+	<hr>
+{/each}
+
+<form action="?/create" method=post use:enhance>
+	<button type=submit>Add</button>
+</form>

src/routes/(v2)/v2/multiple-forms/Form.svelte

@@ -0,0 +1,28 @@
+<script lang="ts">
+	import type { SuperForm } from '$lib/index.js';
+	import type { schema } from './schema.js';
+	import { z } from 'zod';
+	import SuperDebug from '$lib/client/SuperDebug.svelte';
+
+	let { superform }: {
+		superform: SuperForm<z.infer<typeof schema>>;
+	} = $props();
+
+	let { form, message, enhance } = superform;
+</script>
+
+<form action="?/save" method="post" use:enhance>
+	<input type="hidden" name="id" value={$form.id} />
+
+	<SuperDebug data={$form} />
+
+	<label>
+		<input type="text" name="label" bind:value={$form.label} />
+	</label>
+
+	<button type="submit">Save</button>
+
+	{#if $message}
+		<p>{$message}</p>
+	{/if}
+</form>

src/routes/(v2)/v2/multiple-forms/schema.ts

@@ -0,0 +1,6 @@
+import { z } from 'zod';
+
+export const schema = z.object({
+	id: z.number(),
+	label: z.string()
+});