chore: better async derived labels

packages/svelte/src/internal/client/dev/debug.js

@@ -514,3 +514,16 @@
 
 	return true;
 }
+
+/**
+ * Stringify a derived function, removing `$.track_reactivity_loss` and `$.get` etc
+ * @param {Function} fn
+ */
+export function stringify_derived(fn) {
+	return `{${fn.toString()
+		.replace(/^async \(\) => /, '')
+		.replace(/^\(/, '')
+		.replace(/\$\.get\((.+?)\)/, (_, name) => name)
+		.replace(/\$\.track_reactivity_loss\((.+?)\)\(\)/, (_, name) => name)
+		.replace(/\)$/, '')}}`;
+}

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

@@ -47,6 +47,7 @@ import { batch_values, current_batch, previous_batch } from './batch.js';
 import { increment_pending, unset_context } from './async.js';
 import { deferred, includes, noop } from '../../shared/utils.js';
 import { set_signal_status, update_derived_status } from './status.js';
+import { stringify_derived } from '../dev/debug.js';
 
 /**
  * This allows us to track 'reactivity loss' that occurs when signals
@@ -120,7 +121,7 @@ export function async_derived(fn, label, location) {
 	var promise = /** @type {Promise<V>} */ (/** @type {unknown} */ (undefined));
 	var signal = source(/** @type {V} */ (UNINITIALIZED));
 
-	if (DEV) signal.label = label ?? fn.toString();
+	if (DEV) signal.label = label ?? stringify_derived(fn);
 
 	// only suspend in async deriveds created on initialisation
 	var should_suspend = !active_reaction;