Fix: The problem getViteConfig() duplicates some config (#12312)

Co-authored-by: Emanuele Stoppa <my.burning@gmail.com>
Co-authored-by: bluwy <bjornlu.dev@gmail.com>

.changeset/slimy-sloths-fry.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fixes an issue where using `getViteConfig()` returns incorrect and duplicate configuration

packages/astro/src/core/middleware/vite-plugin.ts

@@ -21,9 +21,8 @@ export function vitePluginMiddleware({ settings }: { settings: AstroSettings }):
 
 	return {
 		name: '@astro/plugin-middleware',
-		config(opts, { command }) {
+		config(_, { command }) {
 			isCommandBuild = command === 'build';
-			return opts;
 		},
 		async resolveId(id) {
 			if (id === MIDDLEWARE_MODULE_ID) {

packages/astro/test/config-vite.test.js

@@ -2,6 +2,8 @@ import assert from 'node:assert/strict';
 import { before, describe, it } from 'node:test';
 import * as cheerio from 'cheerio';
 import { loadFixture } from './test-utils.js';
+import { getViteConfig } from '../dist/config/index.js'
+import { resolveConfig } from 'vite';
 
 describe('Vite Config', async () => {
 	let fixture;
@@ -21,3 +23,14 @@ describe('Vite Config', async () => {
 		assert.match($('link').attr('href'), /\/assets\/testing-[a-z\d]+\.css/);
 	});
 });
+
+describe("getViteConfig", () => {
+	it("Does not change the default config.", async () => {
+		const command = "serve";
+		const mode = "test";
+		const configFn = getViteConfig({});
+		const config = await configFn({ command, mode });
+		const resolvedConfig = await resolveConfig(config, command, mode);
+		assert.deepStrictEqual(resolvedConfig.resolve.conditions, ["astro"]);
+	})
+});