feat: attach Svelte major version info to window global (#8761)

Can be opt out by setting discloseVersion to false

---------

Co-authored-by: Simon H <5968653+dummdidumm@users.noreply.github.com>
Co-authored-by: Ben McCann <322311+benmccann@users.noreply.github.com>

.changeset/yellow-squids-explain.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+feat: add version info to `window`. You can opt out by setting `discloseVersion` to `false` in the compiler options

packages/playground/src/App.svelte

@@ -1,3 +1,7 @@
+<script>
+    import Counter from "./lib/Counter.svelte";
+</script>
+
 <div>
     Hello world!
 </div>

packages/svelte/package.json

@@ -56,6 +56,9 @@
       "types": "./types/index.d.ts",
       "import": "./src/runtime/store/index.js"
     },
+    "./internal/disclose-version": {
+      "import": "./src/runtime/internal/disclose-version/index.js"
+    },
     "./transition": {
       "types": "./types/index.d.ts",
       "import": "./src/runtime/transition/index.js"

packages/svelte/scripts/generate-version.js

@@ -13,5 +13,6 @@ fs.writeFileSync(
  * @type {string}
  */
 export const VERSION = '${pkg.version}';
+export const PUBLIC_VERSION = '${pkg.version.split('.')[0]}';
 `
 );

packages/svelte/src/compiler/compile/index.js

@@ -30,7 +30,8 @@ const valid_options = [
 	'loopGuardTimeout',
 	'preserveComments',
 	'preserveWhitespace',
-	'cssHash'
+	'cssHash',
+	'discloseVersion'
 ];
 const valid_css_values = [true, false, 'injected', 'external', 'none'];
 const regex_valid_identifier = /^[a-zA-Z_$][a-zA-Z_$0-9]*$/;
@@ -112,6 +113,10 @@ function validate_options(options, warnings) {
 			throw new Error(`Invalid namespace '${namespace}'`);
 		}
 	}
+
+	if (options.discloseVersion == undefined) {
+		options.discloseVersion = true;
+	}
 }
 
 /**

packages/svelte/src/compiler/compile/render_dom/index.js

@@ -604,5 +604,17 @@ export default function dom(component, options) {
 			);
 		}
 	}
+
+	if (options.discloseVersion === true) {
+		component.imports.unshift({
+			type: 'ImportDeclaration',
+			specifiers: [],
+			source: {
+				type: 'Literal',
+				value: `${options.sveltePath ?? 'svelte'}/internal/disclose-version`
+			}
+		});
+	}
+
 	return { js: flatten(body), css };
 }

packages/svelte/src/compiler/interfaces.d.ts

@@ -344,6 +344,12 @@ export interface CompileOptions {
 	 * @default false
 	 */
 	preserveWhitespace?: boolean;
+	/**
+	 *  If `true`, exposes the Svelte major version on the global `window` object in the browser.
+	 *
+	 * @default true
+	 */
+	discloseVersion?: boolean;
 }
 
 export interface ParserOptions {

packages/svelte/src/runtime/internal/disclose-version/index.js

@@ -0,0 +1,5 @@
+import { PUBLIC_VERSION } from '../../../shared/version.js';
+
+if (typeof window !== 'undefined')
+	// @ts-ignore
+	(window.__svelte || (window.__svelte = { v: new Set() })).v.add(PUBLIC_VERSION);

packages/svelte/src/shared/version.js

@@ -7,3 +7,4 @@
  * @type {string}
  */
 export const VERSION = '4.0.0-next.2';
+export const PUBLIC_VERSION = '4';

packages/svelte/test/helpers.js

@@ -147,6 +147,7 @@ export function create_loader(compileOptions, cwd) {
 			// any imported Svelte components as well. A few edge cases aren't handled but also
 			// currently unused in the tests, for example `export * from`and live bindings.
 			let transformed = compiled.js.code
+				.replace(/^import ['"]([^'"]+)['"]/gm, 'await __import("$1")')
 				.replace(
 					/^import \* as (\w+) from ['"]([^'"]+)['"];?/gm,
 					'const $1 = await __import("$2");'

packages/svelte/test/js/js-output.test.js

@@ -33,7 +33,12 @@ describe('js-output', () => {
 			let actual;
 
 			try {
-				const options = Object.assign({}, config.options || {});
+				const options = Object.assign(
+					{
+						discloseVersion: false
+					},
+					config.options || {}
+				);
 
 				actual = svelte
 					.compile(input, options)

packages/svelte/test/runtime-browser/browser.test.js

@@ -6,8 +6,7 @@ import * as svelte from 'svelte/compiler';
 import { afterAll, assert, beforeAll, describe, it } from 'vitest';
 import { pretty_print_browser_assertion, try_load_config } from '../helpers.js';
 
-const internal = path.resolve('src/runtime/internal/index.js');
-const index = path.resolve('src/runtime/index.js');
+const assert_file = path.resolve(__dirname, 'assert.js');
 
 /** @type {import('@playwright/test').Browser} */
 let browser;
@@ -62,9 +61,7 @@ async function run_browser_test(dir) {
 			alias: {
 				__MAIN_DOT_SVELTE__: path.resolve(__dirname, 'samples', dir, 'main.svelte'),
 				__CONFIG__: path.resolve(__dirname, 'samples', dir, '_config.js'),
-				'assert.js': path.resolve(__dirname, 'assert.js'),
-				'svelte/internal': internal,
-				svelte: index
+				'assert.js': assert_file
 			},
 			plugins: [
 				{
@@ -169,9 +166,7 @@ async function run_custom_elements_test(dir) {
 			entryPoints: [`${cwd}/test.js`],
 			write: false,
 			alias: {
-				'assert.js': path.resolve(__dirname, 'assert.js'),
-				'svelte/internal': internal,
-				svelte: index
+				'assert.js': assert_file
 			},
 			plugins: [
 				{