don't warn about window.fetch during hydration

.changeset/young-scissors-collect.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+don't warn about window.fetch during hydration

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

@@ -8,10 +8,10 @@ import {
 	find_anchor,
 	get_base_uri,
 	get_href,
-	initial_fetch,
 	notifiable_store,
 	scroll_state
 } from './utils.js';
+import * as fetcher from './fetcher.js';
 import { parse } from './parse.js';
 
 import Root from '__GENERATED__/root.svelte';
@@ -48,33 +48,6 @@ function update_scroll_positions(index) {
 	scroll_positions[index] = scroll_state();
 }
 
-const fetch = window.fetch;
-let loading = 0;
-
-if (import.meta.env.DEV) {
-	let can_inspect_stack_trace = false;
-
-	const check_stack_trace = async () => {
-		const stack = /** @type {string} */ (new Error().stack);
-		can_inspect_stack_trace = stack.includes('check_stack_trace');
-	};
-
-	check_stack_trace();
-
-	window.fetch = (input, init) => {
-		const url = input instanceof Request ? input.url : input.toString();
-		const stack = /** @type {string} */ (new Error().stack);
-
-		const heuristic = can_inspect_stack_trace ? stack.includes('load_node') : loading;
-		if (heuristic) {
-			console.warn(
-				`Loading ${url} using \`window.fetch\`. For best results, use the \`fetch\` that is passed to your \`load\` function: https://kit.svelte.dev/docs/loading#input-fetch`
-			);
-		}
-		return fetch(input, init);
-	};
-}
-
 /**
  * @param {{
  *   target: Element;
@@ -621,7 +594,7 @@ export function create_client({ target, session, base, trailing_slash }) {
 					add_dependency(normalized);
 
 					// prerendered pages may be served from any origin, so `initial_fetch` urls shouldn't be normalized
-					return started ? fetch(normalized, init) : initial_fetch(requested, init);
+					return started ? fetcher.native(normalized, init) : fetcher.initial(requested, init);
 				},
 				status: status ?? null,
 				error: error ?? null
@@ -640,10 +613,10 @@ export function create_client({ target, session, base, trailing_slash }) {
 
 			if (import.meta.env.DEV) {
 				try {
-					loading += 1;
+					fetcher.increment();
 					loaded = await module.load.call(null, load_input);
 				} finally {
-					loading -= 1;
+					fetcher.decrement();
 				}
 			} else {
 				loaded = await module.load.call(null, load_input);
@@ -731,7 +704,7 @@ export function create_client({ target, session, base, trailing_slash }) {
 					const is_shadow_page = has_shadow && i === a.length - 1;
 
 					if (is_shadow_page) {
-						const res = await fetch(
+						const res = await fetcher.native(
 							`${url.pathname}${url.pathname.endsWith('/') ? '' : '/'}__data.json${url.search}`,
 							{
 								headers: {

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

@@ -0,0 +1,59 @@
+import { hash } from '../hash.js';
+
+let loading = 0;
+
+export const native = window.fetch;
+
+export function increment() {
+	loading += 1;
+}
+
+export function decrement() {
+	loading -= 1;
+}
+
+if (import.meta.env.DEV) {
+	let can_inspect_stack_trace = false;
+
+	const check_stack_trace = async () => {
+		const stack = /** @type {string} */ (new Error().stack);
+		can_inspect_stack_trace = stack.includes('check_stack_trace');
+	};
+
+	check_stack_trace();
+
+	window.fetch = (input, init) => {
+		const url = input instanceof Request ? input.url : input.toString();
+		const stack = /** @type {string} */ (new Error().stack);
+
+		const heuristic = can_inspect_stack_trace ? stack.includes('load_node') : loading;
+		if (heuristic) {
+			console.warn(
+				`Loading ${url} using \`window.fetch\`. For best results, use the \`fetch\` that is passed to your \`load\` function: https://kit.svelte.dev/docs/loading#input-fetch`
+			);
+		}
+		return native(input, init);
+	};
+}
+
+/**
+ * @param {RequestInfo} resource
+ * @param {RequestInit} [opts]
+ */
+export function initial(resource, opts) {
+	const url = JSON.stringify(typeof resource === 'string' ? resource : resource.url);
+
+	let selector = `script[sveltekit\\:data-type="data"][sveltekit\\:data-url=${url}]`;
+
+	if (opts && typeof opts.body === 'string') {
+		selector += `[sveltekit\\:data-body="${hash(opts.body)}"]`;
+	}
+
+	const script = document.querySelector(selector);
+	if (script && script.textContent) {
+		const { body, ...init } = JSON.parse(script.textContent);
+		return Promise.resolve(new Response(body, init));
+	}
+
+	return native(resource, opts);
+}

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

@@ -1,5 +1,4 @@
 import { writable } from 'svelte/store';
-import { hash } from '../hash.js';
 import { assets } from '../paths.js';
 
 /** @param {HTMLDocument} doc */
@@ -115,25 +114,3 @@ export function create_updated_store() {
 		check
 	};
 }
-
-/**
- * @param {RequestInfo} resource
- * @param {RequestInit} [opts]
- */
-export function initial_fetch(resource, opts) {
-	const url = JSON.stringify(typeof resource === 'string' ? resource : resource.url);
-
-	let selector = `script[sveltekit\\:data-type="data"][sveltekit\\:data-url=${url}]`;
-
-	if (opts && typeof opts.body === 'string') {
-		selector += `[sveltekit\\:data-body="${hash(opts.body)}"]`;
-	}
-
-	const script = document.querySelector(selector);
-	if (script && script.textContent) {
-		const { body, ...init } = JSON.parse(script.textContent);
-		return Promise.resolve(new Response(body, init));
-	}
-
-	return fetch(resource, opts);
-}

packages/kit/test/apps/basics/src/routes/load/window-fetch/correct.svelte

@@ -0,0 +1,18 @@
+<script context="module">
+	/** @type {import('./index').Load} */
+	export async function load({ url, fetch }) {
+		const res = await fetch(`${url.origin}/load/window-fetch/data.json`);
+		const { answer } = await res.json();
+
+		return {
+			props: { answer }
+		};
+	}
+</script>
+
+<script>
+	/** @type {number} */
+	export let answer;
+</script>
+
+<h1>{answer}</h1>

packages/kit/test/apps/basics/test/test.js

@@ -1506,21 +1506,30 @@ test.describe.parallel('Load', () => {
 	});
 
 	test('using window.fetch causes a warning', async ({ page, javaScriptEnabled }) => {
-		const warnings = [];
+		if (javaScriptEnabled && process.env.DEV) {
+			const warnings = [];
 
-		page.on('console', (msg) => {
-			if (msg.type() === 'warning') {
-				warnings.push(msg.text());
-			}
-		});
+			page.on('console', (msg) => {
+				if (msg.type() === 'warning') {
+					warnings.push(msg.text());
+				}
+			});
 
-		await page.goto('/load/window-fetch');
-		expect(await page.textContent('h1')).toBe('42');
+			await page.goto('/load/window-fetch/incorrect');
+			expect(await page.textContent('h1')).toBe('42');
 
-		if (javaScriptEnabled && process.env.DEV) {
 			expect(warnings).toContain(
 				'Loading http://localhost:3000/load/window-fetch/data.json using `window.fetch`. For best results, use the `fetch` that is passed to your `load` function: https://kit.svelte.dev/docs/loading#input-fetch'
 			);
+
+			warnings.length = 0;
+
+			await page.goto('/load/window-fetch/correct');
+			expect(await page.textContent('h1')).toBe('42');
+
+			expect(warnings).not.toContain(
+				'Loading http://localhost:3000/load/window-fetch/data.json using `window.fetch`. For best results, use the `fetch` that is passed to your `load` function: https://kit.svelte.dev/docs/loading#input-fetch'
+			);
 		}
 	});
 });