fix: pass Astro config postcss to Svelte preprocess

packages/integrations/svelte/src/index.ts

@@ -1,6 +1,7 @@
 import type { Options } from '@sveltejs/vite-plugin-svelte';
+import type { AstroIntegration, AstroRenderer, AstroConfig } from 'astro';
+import type { UserConfig } from 'vite'
 import { svelte } from '@sveltejs/vite-plugin-svelte';
-import type { AstroIntegration, AstroRenderer } from 'astro';
 import preprocess from 'svelte-preprocess';
 
 function getRenderer(): AstroRenderer {
@@ -11,13 +12,20 @@ function getRenderer(): AstroRenderer {
 	};
 }
 
-function getViteConfiguration(isDev: boolean, options?: Options | OptionsCallback) {
-	const defaultOptions = {
+type ViteConfigurationArgs = {
+	isDev: boolean;
+	options?: Options | OptionsCallback;
+	postcssConfig: AstroConfig['style']['postcss'];
+}
+
+function getViteConfiguration({ options, postcssConfig, isDev }: ViteConfigurationArgs): UserConfig {
+	const defaultOptions: Partial<Options> = {
 		emitCss: true,
 		compilerOptions: { dev: isDev, hydratable: true },
 		preprocess: [
 			preprocess({
 				less: true,
+				postcss: postcssConfig,
 				sass: { renderSync: true },
 				scss: { renderSync: true },
 				stylus: true,
@@ -61,9 +69,15 @@ export default function (options?: Options | OptionsCallback): AstroIntegration
 		name: '@astrojs/svelte',
 		hooks: {
 			// Anything that gets returned here is merged into Astro Config
-			'astro:config:setup': ({ command, updateConfig, addRenderer }) => {
+			'astro:config:setup': ({ command, updateConfig, addRenderer, config }) => {
 				addRenderer(getRenderer());
-				updateConfig({ vite: getViteConfiguration(command === 'dev', options) });
+				updateConfig({
+					vite: getViteConfiguration({
+						options,
+						isDev: command === 'dev',
+						postcssConfig: config.style.postcss,
+					})
+				});
 			},
 		},
 	};