update_reaction() — svelte Function Reference

Source Code

packages/svelte/src/internal/client/runtime.js lines 222–354

export function update_reaction(reaction) {
	var previous_deps = new_deps;
	var previous_skipped_deps = skipped_deps;
	var previous_untracked_writes = untracked_writes;
	var previous_reaction = active_reaction;
	var previous_sources = current_sources;
	var previous_component_context = component_context;
	var previous_untracking = untracking;
	var previous_update_version = update_version;

	var flags = reaction.f;

	new_deps = /** @type {null | Value[]} */ (null);
	skipped_deps = 0;
	untracked_writes = null;
	active_reaction = (flags & (BRANCH_EFFECT | ROOT_EFFECT)) === 0 ? reaction : null;

	current_sources = null;
	set_component_context(reaction.ctx);
	untracking = false;
	update_version = ++read_version;

	if (reaction.ac !== null) {
		without_reactive_context(() => {
			/** @type {AbortController} */ (reaction.ac).abort(STALE_REACTION);
		});

		reaction.ac = null;
	}

	try {
		reaction.f |= REACTION_IS_UPDATING;
		var fn = /** @type {Function} */ (reaction.fn);
		var result = fn();
		var deps = reaction.deps;

		// Don't remove reactions during fork;
		// they must remain for when fork is discarded
		var is_fork = current_batch?.is_fork;

		if (new_deps !== null) {
			var i;

			if (!is_fork) {
				remove_reactions(reaction, skipped_deps);
			}

			if (deps !== null && skipped_deps > 0) {
				deps.length = skipped_deps + new_deps.length;
				for (i = 0; i < new_deps.length; i++) {
					deps[skipped_deps + i] = new_deps[i];
				}
			} else {
				reaction.deps = deps = new_deps;
			}

			if (effect_tracking() && (reaction.f & CONNECTED) !== 0) {
				for (i = skipped_deps; i < deps.length; i++) {
					(deps[i].reactions ??= []).push(reaction);
				}
			}
		} else if (!is_fork && deps !== null && skipped_deps < deps.length) {
			remove_reactions(reaction, skipped_deps);
			deps.length = skipped_deps;
		}

		// If we're inside an effect and we have untracked writes, then we need to
		// ensure that if any of those untracked writes result in re-invalidation
		// of the current effect, then that happens accordingly
		if (
			is_runes() &&
			untracked_writes !== null &&
			!untracking &&
			deps !== null &&
			(reaction.f & (DERIVED | MAYBE_DIRTY | DIRTY)) === 0
		) {
			for (i = 0; i < /** @type {Source[]} */ (untracked_writes).length; i++) {
				schedule_possible_effect_self_invalidation(
					untracked_writes[i],
					/** @type {Effect} */ (reaction)
				);