RFC 0002: Reactive Component Model MVP

Status

Accepted for Stage 4.

Decision

vooya-core provides a single-threaded Signal<T> and explicit Effect API. Signals own a value and notify subscribed effects after set or update. Effects own rendering work. The first proof component, TaskList, uses three signals for tasks, filter selection, and validation errors; one effect renders the component's owned DOM subtree.

let tasks = signal(Vec::<Task>::new());
let render = effect(move || render(tasks.get()));
let _subscription = tasks.subscribe(render.clone());

tasks.update(|items| items.push(task));

Required behavior in this stage

• State changes trigger subscribed effects synchronously.
• Every subscription returns a disposable handle; dropping it unregisters the effect, including when an earlier effect removes a later one during notify.
• Components render only inside their Vooya-owned root.
• Conditional branches are represented by ordinary state-dependent rendering.
• Lists use stable task IDs as DOM keys and move/reuse keyed row roots.
• User input validation is represented as a signal and rendered through an accessible role="alert" node.

The current Rust-file runtime also provides synchronous batch boundaries, owned listener/subscription cleanup, re-entrant effect-cycle protection, and DOM child move/replace primitives. Opt-in dependency tracking is available through tracked_effect; the public rsx! syntax covers keyed for loops and conditional if/else branches.

Non-goals

• Implicit dependency tracking in ordinary effect callbacks.
• Async resources or concurrent render.
• A broader template language beyond the current rsx! forms.
• Fine-grained child reconciliation below a keyed row root.
• Automatic escaping policy beyond the component's use of structured DOM APIs.

The Task List demonstrates that a manually authored Rust component can be meaningful before Vooya commits to a source-level component DSL. A later macro must compile to this runtime contract rather than replace it.