fix: correct first processing of boundary with pending snippet

WIP

packages/svelte/src/internal/client/reactivity/batch.js

@@ -379,7 +379,7 @@ export class Batch {
 	flush() {
 		if (queued_root_effects.length > 0) {
 			flush_effects();
-		} else {
+		} else if (this.#pending === 0) {
 			this.#commit();
 		}
 
@@ -417,20 +417,22 @@ export class Batch {
 		this.#pending -= 1;
 
 		if (this.#pending === 0) {
-			for (const e of this.#dirty_effects) {
-				set_signal_status(e, DIRTY);
-				schedule_effect(e);
-			}
+			Batch.enqueue(() => {
+				for (const e of this.#dirty_effects) {
+					set_signal_status(e, DIRTY);
+					schedule_effect(e);
+				}
 
-			for (const e of this.#maybe_dirty_effects) {
-				set_signal_status(e, MAYBE_DIRTY);
-				schedule_effect(e);
-			}
+				for (const e of this.#maybe_dirty_effects) {
+					set_signal_status(e, MAYBE_DIRTY);
+					schedule_effect(e);
+				}
 
-			this.#render_effects = [];
-			this.#effects = [];
+				this.#render_effects = [];
+				this.#effects = [];
 
-			this.flush();
+				this.flush();
+			});
 		} else {
 			this.deactivate();
 		}
@@ -670,20 +672,14 @@ export function schedule_effect(signal) {
 export function suspend() {
 	var boundary = get_pending_boundary();
 	var batch = /** @type {Batch} */ (current_batch);
-	var pending = boundary.pending;
 
 	boundary.update_pending_count(1);
-	if (!pending) batch.increment();
+	batch.increment();
 
 	return function unsuspend() {
 		boundary.update_pending_count(-1);
-
-		if (!pending) {
-			batch.activate();
-			batch.decrement();
-		} else {
-			batch.deactivate();
-		}
+		batch.activate();
+		batch.decrement();
 
 		unset_context();
 	};
@@ -694,4 +690,5 @@ export function suspend() {
  */
 export function clear() {
 	batches.clear();
+	tasks.length = 0;
 }

packages/svelte/src/internal/client/reactivity/deriveds.js

@@ -135,11 +135,10 @@ export function async_derived(fn, location) {
 		prev = promise;
 
 		var batch = /** @type {Batch} */ (current_batch);
-		var pending = boundary.pending;
 
 		if (should_suspend) {
 			boundary.update_pending_count(1);
-			if (!pending) batch.increment();
+			batch.increment();
 		}
 
 		/**
@@ -151,7 +150,7 @@ export function async_derived(fn, location) {
 
 			current_async_effect = null;
 
-			if (!pending) batch.activate();
+			batch.activate();
 
 			if (error) {
 				if (error !== STALE_REACTION) {
@@ -181,7 +180,7 @@ export function async_derived(fn, location) {
 
 			if (should_suspend) {
 				boundary.update_pending_count(-1);
-				if (!pending) batch.decrement();
+				batch.decrement();
 			}
 
 			unset_context();