fix: replace version in generateBundle

.changeset/moody-zoos-compare.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: ensure a changing `version` doesn't affect the hashes for chunks without any actual code changes

packages/kit/src/constants.js

@@ -9,3 +9,15 @@ export const GENERATED_COMMENT = '// this file is generated — do not edit it\n
 export const ENDPOINT_METHODS = ['GET', 'POST', 'PUT', 'PATCH', 'DELETE', 'OPTIONS', 'HEAD'];
 
 export const PAGE_METHODS = ['GET', 'POST', 'HEAD'];
+
+/**
+ * Placeholders for the hash of the app version.
+ * Later replaced in the generateBundle hook to avoid affecting the chunk hash.
+ */
+export const APP_VERSION_HASH_PLACEHOLDER_BASE = '__SVELTEKIT_APP_VERSION_HASH__';
+
+/**
+ * Placeholder for the app version.
+ * Later replaced in the generateBundle hook to avoid affecting the chunk hash.
+ */
+export const APP_VERSION_PLACEHOLDER_BASE = '__SVELTEKIT_APP_VERSION__';

packages/kit/src/exports/vite/index.js

@@ -35,6 +35,10 @@ import {
 	sveltekit_server
 } from './module_ids.js';
 import { resolve_peer_dependency } from '../../utils/import.js';
+import {
+	APP_VERSION_PLACEHOLDER_BASE,
+	APP_VERSION_HASH_PLACEHOLDER_BASE
+} from '../../constants.js';
 
 const cwd = process.cwd();
 
@@ -184,7 +188,16 @@ async function kit({ svelte_config }) {
 	const { kit } = svelte_config;
 	const out = `${kit.outDir}/output`;
 
-	const version_hash = hash(kit.version.name);
+	const app_version = kit.version.name;
+	const version_hash = hash(app_version);
+
+	// if the app version or hash is longer than the placeholder, we need to pad it to avoid
+	// source map damage
+	const app_version_placeholder = APP_VERSION_PLACEHOLDER_BASE.padEnd(app_version.length, '_');
+	const app_version_hash_placeholder = APP_VERSION_HASH_PLACEHOLDER_BASE.padEnd(
+		version_hash.length,
+		'_'
+	);
 
 	/** @type {import('vite').ResolvedConfig} */
 	let vite_config;
@@ -384,7 +397,7 @@ async function kit({ svelte_config }) {
 			const browser = !options?.ssr;
 
 			const global = is_build
-				? `globalThis.__sveltekit_${version_hash}`
+				? `globalThis.__sveltekit_${browser ? app_version_hash_placeholder : version_hash}`
 				: 'globalThis.__sveltekit_dev';
 
 			if (options?.ssr === false && process.env.TEST !== 'true') {
@@ -470,10 +483,8 @@ async function kit({ svelte_config }) {
 				}
 
 				case sveltekit_environment: {
-					const { version } = svelte_config.kit;
-
 					return dedent`
-						export const version = ${s(version.name)};
+						export const version = ${is_build && browser ? app_version_placeholder : s(kit.version.name)};
 						export let building = false;
 						export let prerendering = false;
 
@@ -923,7 +934,50 @@ async function kit({ svelte_config }) {
 		}
 	};
 
-	return [plugin_setup, plugin_virtual_modules, plugin_guard, plugin_compile];
+	/** @type {import('vite').Plugin} */
+	const plugin_replace_version_and_hash = {
+		name: 'vite-plugin-svelte-replace-version-and-hash',
+		enforce: 'post',
+
+		generateBundle(_, bundle, __) {
+			if (vite_config.build.ssr) return;
+
+			for (const file in bundle) {
+				if (bundle[file].type !== 'chunk') continue;
+				const chunk = /** @type {import('rollup').OutputChunk} */ (bundle[file]);
+				let code = chunk.code;
+				if (
+					!(code.includes(app_version_placeholder) || code.includes(app_version_hash_placeholder))
+				)
+					continue;
+
+				// replace the version and version after the chunk hash has already been calculated
+				// to avoid affecting the chunk hash
+				const substitutions = [
+					[app_version_hash_placeholder, version_hash],
+					[app_version_placeholder, JSON.stringify(kit.version.name)]
+				];
+
+				for (const [placeholder, replacement] of substitutions) {
+					code = code.replaceAll(
+						placeholder,
+						// pad the replacement to mitigate source map changes
+						replacement.padEnd(placeholder.length, ' ')
+					);
+				}
+
+				chunk.code = code;
+			}
+		}
+	};
+
+	return [
+		plugin_setup,
+		plugin_virtual_modules,
+		plugin_guard,
+		plugin_compile,
+		plugin_replace_version_and_hash
+	];
 }
 
 /**