fix: overriding parent values breaks reactivity

[Refzlund]

No description provided.

[Copilot]

Pull Request Overview

This PR addresses broken reactivity when a parent object’s value is overridden by introducing a new “prescriptor” mechanism to keep nested objects and arrays in sync.

• Replace manual setValue calls with a new addPrescriptor API in both SvelteValue and SvelteObject to wire get/set callbacks for nested props.
• Refactor component APIs to accept a default prop and explicitly name the children snippet parameters.
• Update Storybook examples and add Tailwind imports to demonstrate and reproduce the override issue.

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
svelte-object/stories/tw.css	Import Tailwind for story styling
svelte-object/stories/issues/overriding-states/README.mdx	Document overriding-parent-value reactivity issue
svelte-object/stories/issues/overriding-states/Issue.stories.svelte	Add reproduction story showing override button
svelte-object/src/SvelteValue.svelte	Remove manual setValue logic and use addPrescriptor
svelte-object/src/SvelteObject.svelte	Introduce addPrescriptor/default and refactor effects
svelte-object/src/SvelteArray.svelte	Rename props, pass new default down to SvelteObject
.changeset/tall-frogs-sleep.md	Bump patch version with fix description

Comments suppressed due to low confidence (1)

svelte-object/src/SvelteArray.svelte:55

• [nitpick] Using default as a prop name can be confusing since it’s a reserved word; consider renaming to defaultValue or initial for clarity.

	default={defaultvalue as T ?? []}

[Copilot]

Typo in documentation: “reactants” should be “reactivity” or “reactive components” to match the issue description.

Suggested change

	When overriding the top-object value reactants such as lower-level arrays and objects stop working.
	When overriding the top-object value reactivity such as lower-level arrays and objects stop working.

[Copilot]

The call to parent.addPrescriptor(...) returns an unsubscribe function which isn’t stored or called on component destroy, potentially causing lingering prescriptors. Consider capturing the return value and calling it in onDestroy.

Suggested change

	if(parent && (name !== undefined && name !== null) && name !== '') {
	parent.addPrescriptor(name, () => value, v => value = v as T)
	let unsubscribePrescriptor: (() => void) | undefined;
	if(parent && (name !== undefined && name !== null) && name !== '') {
	unsubscribePrescriptor = parent.addPrescriptor(name, () => value, v => value = v as T);

[Copilot]

[nitpick] Registering nested $effect.pre callbacks inside a loop on every state change may degrade performance and lead to redundant effect registrations. Consider moving these registrations outside the loop or consolidating the reactive updates.

Suggested change

	for(const prescriptor of prescriptors) {
	$effect.pre(() => {
	prescriptor.set(value?.[prescriptor.name])
	})
	$effect.pre(() => {
	const itemValue = prescriptor.get()
	value ??= {} as T
	prescriptor.name
	untrack(() => {
	value ??= {} as T
	value[prescriptor.name] = itemValue
	})
	})
	}
	})
	value ??= {} as T;
	for (const prescriptor of prescriptors) {
	const itemValue = prescriptor.get();
	prescriptor.set(value?.[prescriptor.name]);
	untrack(() => {
	value[prescriptor.name] = itemValue;
	});
	}
	});

[Refzlund]

Would break reactivity and the efficiency of such.