From 158a242f90dc7bbc77d989b1cdcb049f00b28e39 Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Tue, 10 Jun 2025 20:56:22 -0400
Subject: [PATCH] tidy up types, fix duplication

---
 .../svelte/src/internal/client/dev/tracing.js | 22 ++++++++-----------
 .../svelte/src/internal/client/runtime.js     | 21 +++++++++++++-----
 2 files changed, 24 insertions(+), 19 deletions(-)

diff --git a/packages/svelte/src/internal/client/dev/tracing.js b/packages/svelte/src/internal/client/dev/tracing.js
index 88d1907a26..d66e4e46ae 100644
--- a/packages/svelte/src/internal/client/dev/tracing.js
+++ b/packages/svelte/src/internal/client/dev/tracing.js
@@ -6,14 +6,14 @@ import { DERIVED, PROXY_PATH_SYMBOL, STATE_SYMBOL } from '#client/constants';
 import { effect_tracking } from '../reactivity/effects.js';
 import { active_reaction, captured_signals, set_captured_signals, untrack } from '../runtime.js';
 
-/** @type {{ reaction: Reaction | null, entries: Map<any, any> } | null} */
+/** @type {{ reaction: Reaction | null, entries: Map<Value, Error[]> } | null} */
 export let tracing_expressions = null;
 
 /**
- * @param { Value } signal
- * @param { { read: Error[] } } [entry]
+ * @param {Value} signal
+ * @param {Error[]} [traces]
  */
-function log_entry(signal, entry) {
+function log_entry(signal, traces = []) {
 	const debug = signal.debug;
 	const value = signal.trace_need_increase ? signal.trace_v : signal.v;
 
@@ -74,13 +74,9 @@ function log_entry(signal, entry) {
 		console.log(signal.updated);
 	}
 
-	const read = entry?.read;
-
-	if (read && read.length > 0) {
-		for (var stack of read) {
-			// eslint-disable-next-line no-console
-			console.log(stack);
-		}
+	for (var trace of traces) {
+		// eslint-disable-next-line no-console
+		console.log(trace);
 	}
 
 	// eslint-disable-next-line no-console
@@ -116,8 +112,8 @@ export function trace(label, fn) {
 
 			tracing_expressions = null;
 
-			for (const [signal, entry] of entries) {
-				log_entry(signal, entry);
+			for (const [signal, traces] of entries) {
+				log_entry(signal, traces);
 			}
 			// eslint-disable-next-line no-console
 			console.groupEnd();
diff --git a/packages/svelte/src/internal/client/runtime.js b/packages/svelte/src/internal/client/runtime.js
index 51402ac88c..528db059e8 100644
--- a/packages/svelte/src/internal/client/runtime.js
+++ b/packages/svelte/src/internal/client/runtime.js
@@ -783,14 +783,23 @@ export function get(signal) {
 		if (signal.debug) {
 			signal.debug();
 		} else if (signal.created) {
-			var entry = tracing_expressions.entries.get(signal);
+			var trace = get_stack('TracedAt');
 
-			if (entry === undefined) {
-				entry = { read: [] };
-				tracing_expressions.entries.set(signal, entry);
-			}
+			if (trace) {
+				var traces = tracing_expressions.entries.get(signal);
+
+				if (traces === undefined) {
+					tracing_expressions.entries.set(signal, (traces = []));
+				}
 
-			entry.read.push(get_stack('TracedAt'));
+				var last = traces.at(-1);
+
+				// traces can be duplicated, e.g. by `snapshot` invoking both
+				// both `getOwnPropertyDescriptor` and `get` traps at once
+				if (trace.stack !== last?.stack) {
+					traces.push(trace);
+				}
+			}
 		}
 	}