Method schedule

packages/svelte/src/internal/client/reactivity/batch.js:921–972

* * @param {Effect} effect

(effect)

	 * @param {Effect} effect
	 */
	schedule(effect) {
		last_scheduled_effect = effect;

		// defer render effects inside a pending boundary
		// TODO the `REACTION_RAN` check is only necessary because of legacy `$:` effects AFAICT — we can remove later
		if (
			effect.b?.is_pending &&
			(effect.f & (EFFECT | RENDER_EFFECT | MANAGED_EFFECT)) !== 0 &&
			(effect.f & REACTION_RAN) === 0
		) {
			effect.b.defer_effect(effect);
			return;
		}

		var e = effect;

		while (e.parent !== null) {
			e = e.parent;
			var flags = e.f;

			// if the effect is being scheduled because a parent (each/await/etc) block
			// updated an internal source, or because a branch is being unskipped,
			// bail out or we'll cause a second flush
			if (collected_effects !== null && e === active_effect) {
				if (async_mode_flag) return;

				// in sync mode, render effects run during traversal. in an extreme edge case
				// — namely that we're setting a value inside a derived read during traversal —
				// they can be made dirty after they have already been visited, in which
				// case we shouldn't bail out. we also shouldn't bail out if we're
				// updating a store inside a `$:`, since this might invalidate
				// effects that were already visited
				if (
					(active_reaction === null || (active_reaction.f & DERIVED) === 0) &&
					!legacy_is_updating_store
				) {
					return;
				}
			}

			if ((flags & (ROOT_EFFECT | BRANCH_EFFECT)) !== 0) {
				if ((flags & CLEAN) === 0) {
					// branch is already dirty, bail
					return;
				}

				e.f ^= CLEAN;
			}
		}

		this.#roots.push(e);
	}

	#unlink() {
		// #merge calls #unlink, discard later on does it again - prevent