fix: don't stash away original history methods so other libs can monkeypatch it

.changeset/bright-moose-brake.md

@@ -0,0 +1,5 @@
+---
+"@sveltejs/kit": patch
+---
+
+fix: don't stash away original `history` methods so other libs can monkeypatch it

packages/kit/src/runtime/client/client.js

@@ -64,29 +64,37 @@ const scroll_positions = storage.get(SCROLL_KEY) ?? {};
  */
 const snapshots = storage.get(SNAPSHOT_KEY) ?? {};
 
-const original_push_state = BROWSER ? history.pushState : () => {};
-const original_replace_state = BROWSER ? history.replaceState : () => {};
-
 if (DEV && BROWSER) {
 	let warned = false;
 
 	const warn = () => {
 		if (warned) return;
+
+		// Rather than saving a pointer to the original history methods, which would prevent monkeypatching by other libs,
+		// inspect the stack trace to see if we're being called from within SvelteKit.
+		let stack = new Error().stack?.split('\n');
+		if (!stack) return;
+		if (!stack[0].includes('https:') && !stack[0].includes('http:')) stack = stack.slice(1); // Chrome includes the error message in the stack
+		stack = stack.slice(2); // remove `warn` and the place where `warn` was called
+		if (stack[0].includes(import.meta.url)) return;
+
 		warned = true;
 
 		console.warn(
 			"Avoid using `history.pushState(...)` and `history.replaceState(...)` as these will conflict with SvelteKit's router. Use the `pushState` and `replaceState` imports from `$app/navigation` instead."
 		);
 	};
 
+	const push_state = history.pushState;
 	history.pushState = (...args) => {
 		warn();
-		return original_push_state.apply(history, args);
+		return push_state.apply(history, args);
 	};
 
+	const replace_state = history.replaceState;
 	history.replaceState = (...args) => {
 		warn();
-		return original_replace_state.apply(history, args);
+		return replace_state.apply(history, args);
 	};
 }
 
@@ -252,8 +260,7 @@ export async function start(_app, _target, hydrate) {
 		current_history_index = current_navigation_index = Date.now();
 
 		// create initial history entry, so we can return here
-		original_replace_state.call(
-			history,
+		history.replaceState(
 			{
 				...history.state,
 				[HISTORY_INDEX]: current_history_index,
@@ -1296,7 +1303,7 @@ async function navigate({
 			[STATES_KEY]: state
 		};
 
-		const fn = replace_state ? original_replace_state : original_push_state;
+		const fn = replace_state ? history.replaceState : history.pushState;
 		fn.call(history, entry, '', url);
 
 		if (!replace_state) {
@@ -1812,7 +1819,7 @@ export function pushState(url, state) {
 		[STATES_KEY]: state
 	};
 
-	original_push_state.call(history, opts, '', resolve_url(url));
+	history.pushState(opts, '', resolve_url(url));
 
 	page = { ...page, state };
 	root.$set({ page });
@@ -1849,7 +1856,7 @@ export function replaceState(url, state) {
 		[STATES_KEY]: state
 	};
 
-	original_replace_state.call(history, opts, '', resolve_url(url));
+	history.replaceState(opts, '', resolve_url(url));
 
 	page = { ...page, state };
 	root.$set({ page });
@@ -2180,8 +2187,7 @@ function _start_router() {
 		// we need to update history, otherwise we have to leave it alone
 		if (hash_navigating) {
 			hash_navigating = false;
-			original_replace_state.call(
-				history,
+			history.replaceState(
 				{
 					...history.state,
 					[HISTORY_INDEX]: ++current_history_index,

packages/kit/src/runtime/client/fetcher.js

@@ -17,6 +17,7 @@ export function unlock_fetch() {
 if (DEV && BROWSER) {
 	let can_inspect_stack_trace = false;
 
+	// detect whether async stack traces work
 	const check_stack_trace = async () => {
 		const stack = /** @type {string} */ (new Error().stack);
 		can_inspect_stack_trace = stack.includes('check_stack_trace');