fix: improve $inspect batching (#9902)

* fix: improve $inspect batching

* fix dev bug

* simplify

* simplify

.changeset/heavy-ears-rule.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: improve $inspect batching

packages/svelte/src/internal/client/proxy/proxy.js

@@ -7,7 +7,8 @@ import {
 	source,
 	updating_derived,
 	UNINITIALIZED,
-	mutable_source
+	mutable_source,
+	batch_inspect
 } from '../runtime.js';
 import {
 	define_property,
@@ -166,8 +167,17 @@ const handler = {
 			metadata.s.set(prop, s);
 		}
 
-		const value = s !== undefined ? get(s) : Reflect.get(target, prop, receiver);
-		return value === UNINITIALIZED ? undefined : value;
+		if (s !== undefined) {
+			const value = get(s);
+			return value === UNINITIALIZED ? undefined : value;
+		}
+
+		if (DEV) {
+			if (typeof target[prop] === 'function' && prop !== Symbol.iterator) {
+				return batch_inspect(target, prop, receiver);
+			}
+		}
+		return Reflect.get(target, prop, receiver);
 	},
 
 	getOwnPropertyDescriptor(target, prop) {

packages/svelte/src/internal/client/runtime.js

@@ -37,6 +37,8 @@ let current_scheduler_mode = FLUSH_MICROTASK;
 // Used for handling scheduling
 let is_micro_task_queued = false;
 let is_task_queued = false;
+// Used for $inspect
+export let is_batching_effect = false;
 
 // Handle effect queues
 
@@ -62,8 +64,8 @@ let current_dependencies = null;
 let current_dependencies_index = 0;
 /** @type {null | import('./types.js').Signal[]} */
 let current_untracked_writes = null;
-// Handling capturing of signals from object property getters
-let current_should_capture_signal = false;
+/** @type {null | import('./types.js').Signal} */
+let last_inspected_signal = null;
 /** If `true`, `get`ting the signal should not register it as a dependency */
 export let current_untracking = false;
 /** Exists to opt out of the mutation validation for stores which may be set for the first time during a derivation */
@@ -110,6 +112,29 @@ function is_runes(context) {
 	return component_context !== null && component_context.r;
 }
 
+/**
+ * @param {import("./proxy/proxy.js").StateObject} target
+ * @param {string | symbol} prop
+ * @param {any} receiver
+ */
+export function batch_inspect(target, prop, receiver) {
+	const value = Reflect.get(target, prop, receiver);
+	return function () {
+		const previously_batching_effect = is_batching_effect;
+		is_batching_effect = true;
+		try {
+			return Reflect.apply(value, receiver, arguments);
+		} finally {
+			is_batching_effect = previously_batching_effect;
+			if (last_inspected_signal !== null) {
+				// @ts-expect-error
+				for (const fn of last_inspected_signal.inspect) fn();
+				last_inspected_signal = null;
+			}
+		}
+	};
+}
+
 /**
  * @param {null | import('./types.js').ComponentContext} context_stack_item
  * @returns {void}
@@ -1053,8 +1078,12 @@ export function set_signal_value(signal, value) {
 
 		// @ts-expect-error
 		if (DEV && signal.inspect) {
-			// @ts-expect-error
-			for (const fn of signal.inspect) fn();
+			if (is_batching_effect) {
+				last_inspected_signal = signal;
+			} else {
+				// @ts-expect-error
+				for (const fn of signal.inspect) fn();
+			}
 		}
 	}
 }