chore: add tests for treeshaking (#13909)

* add tests

* format

* Update packages/kit/test/apps/basics/src/routes/treeshaking/dev/+page.svelte

Co-authored-by: Dominik G. <dominik.goepel@gmx.de>

* Update packages/kit/test/apps/basics/src/routes/treeshaking/browser/+page.svelte

Co-authored-by: Dominik G. <dominik.goepel@gmx.de>

* fix

* ok this is the one

* Update server.test.js

---------

Co-authored-by: Dominik G. <dominik.goepel@gmx.de>
Co-authored-by: Simon H <5968653+dummdidumm@users.noreply.github.com>

Author: 3 people

packages/kit/test/apps/basics/src/routes/treeshaking/browser/+page.svelte

@@ -0,0 +1,10 @@
+<script>
+	import { browser } from '$app/environment';
+</script>
+
+<p>
+	{browser ? 'client' : 'server'}
+</p>
+<p>
+	negated: {!browser ? 'server' : 'client'}
+</p>

packages/kit/test/apps/basics/src/routes/treeshaking/dev/+page.svelte

@@ -0,0 +1,6 @@
+<script>
+	import { dev } from '$app/environment';
+</script>
+
+<p>{dev ? 'not prod' : 'prod'}</p>
+<p>negated: {!dev ? 'prod' : 'not prod'}</p>

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

@@ -2,6 +2,9 @@ import process from 'node:process';
 import { expect } from '@playwright/test';
 import { test } from '../../../utils.js';
 import { createHash, randomBytes } from 'node:crypto';
+import fs from 'node:fs';
+import { fileURLToPath } from 'node:url';
+import path from 'node:path';
 
 /** @typedef {import('@playwright/test').Response} Response */
 
@@ -736,3 +739,32 @@ test.describe('$app/forms', () => {
 		expect(await response.json()).toEqual({ data: 'It works!' });
 	});
 });
+
+const root = path.resolve(fileURLToPath(import.meta.url), '..', '..');
+
+test.describe('$app/environment', () => {
+	test('treeshakes dev check', async () => {
+		test.skip(!!process.env.DEV, 'skip when in dev mode');
+
+		const code = fs.readFileSync(
+			path.join(root, '.svelte-kit/output/server/entries/pages/treeshaking/dev/_page.svelte.js'),
+			'utf-8'
+		);
+		// check that import { dev } from '$app/environment' is treeshaken
+		expect(code).not.toContain('dev');
+	});
+
+	test('treeshakes browser check', async () => {
+		test.skip(!!process.env.DEV, 'skip when in dev mode');
+
+		const code = fs.readFileSync(
+			path.join(
+				root,
+				'.svelte-kit/output/server/entries/pages/treeshaking/browser/_page.svelte.js'
+			),
+			'utf-8'
+		);
+		// check that import { browser } from '$app/environment' is treeshaken
+		expect(code).not.toContain('browser');
+	});
+});