chore: simplify infinite_loop_guard

Author: Rich-Harris

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

@@ -64,13 +64,12 @@ function dequeue() {
 /** @type {Effect[]} */
 let queued_root_effects = [];
 
-/** @type {Effect | null} */
-let last_scheduled_effect = null;
-
 let is_flushing = false;
 
 let is_flushing_sync = false;
 
+let flush_count = 0;
+
 export class Batch {
 	/**
 	 * The current values of any sources that are updated in this batch
@@ -463,10 +462,6 @@ export function flushSync(fn) {
 
 				// we need to check again, in case we just updated an `$effect.pending()`
 				if (queued_root_effects.length === 0) {
-					// this would be reset in `flush_effects()` but since we are early returning here,
-					// we need to reset it here as well in case the first time there's 0 queued root effects
-					last_scheduled_effect = null;
-
 					return /** @type {T} */ (result);
 				}
 			}
@@ -483,46 +478,16 @@ function flush_effects() {
 	is_flushing = true;
 
 	try {
-		var flush_count = 0;
+		flush_count = 0;
 		set_is_updating_effect(true);
 
 		while (queued_root_effects.length > 0) {
-			var batch = Batch.ensure();
-
-			if (flush_count++ > 1000) {
-				if (DEV) {
-					var updates = new Map();
-
-					for (const source of batch.current.keys()) {
-						for (const [stack, update] of source.updated ?? []) {
-							var entry = updates.get(stack);
-
-							if (!entry) {
-								entry = { error: update.error, count: 0 };
-								updates.set(stack, entry);
-							}
-
-							entry.count += update.count;
-						}
-					}
-
-					for (const update of updates.values()) {
-						// eslint-disable-next-line no-console
-						console.error(update.error);
-					}
-				}
-
-				infinite_loop_guard();
-			}
-
-			batch.process(queued_root_effects);
+			Batch.ensure().process(queued_root_effects);
 			old_values.clear();
 		}
 	} finally {
 		is_flushing = false;
 		set_is_updating_effect(was_updating_effect);
-
-		last_scheduled_effect = null;
 	}
 }
 
@@ -537,7 +502,7 @@ function infinite_loop_guard() {
 
 		// Best effort: invoke the boundary nearest the most recent
 		// effect and hope that it's relevant to the infinite loop
-		invoke_error_boundary(error, last_scheduled_effect);
+		invoke_error_boundary(error, active_effect);
 	}
 }
 
@@ -598,7 +563,7 @@ function flush_queued_effects(effects) {
  * @returns {void}
  */
 export function schedule_effect(signal) {
-	var effect = (last_scheduled_effect = signal);
+	var effect = signal;
 
 	while (effect.parent !== null) {
 		effect = effect.parent;
@@ -616,6 +581,34 @@ export function schedule_effect(signal) {
 		}
 	}
 
+	if (queued_root_effects.length === 0 && flush_count++ > 1000) {
+		flush_count = 0;
+
+		if (DEV && current_batch !== null) {
+			var updates = new Map();
+
+			for (const source of current_batch.current.keys()) {
+				for (const [stack, update] of source.updated ?? []) {
+					var entry = updates.get(stack);
+
+					if (!entry) {
+						entry = { error: update.error, count: 0 };
+						updates.set(stack, entry);
+					}
+
+					entry.count += update.count;
+				}
+			}
+
+			for (const update of updates.values()) {
+				// eslint-disable-next-line no-console
+				console.error(update.error);
+			}
+		}
+
+		infinite_loop_guard();
+	}
+
 	queued_root_effects.push(effect);
 }