feat: svelte config (#9061)

* wip: svelte webpack5

* added project svelte config

* svelte snapshot

packages/webpack5/src/configuration/svelte.ts

@@ -1,10 +1,65 @@
 import base from './base';
-import { IWebpackEnv } from '@nativescript/webpack';
+import { env as _env, IWebpackEnv } from '../index';
 import Config from 'webpack-chain';
+import { getPlatform, getProjectRootPath } from '../helpers/project';
+import { merge } from 'webpack-merge';
+import svelteNativePreprocessor from 'svelte-native-preprocessor';
 
-// todo: add base configuration for svelte
-export default function (config: Config, env: IWebpackEnv): Config {
+export default function (config: Config, env: IWebpackEnv = _env): Config {
 	base(config, env);
 
+	const platform = getPlatform();
+	const mode = env.production ? 'production' : 'development';
+	const production = mode === 'production';
+
+	// resolve .svelte files
+	// the order is reversed because we are using prepend!
+	config.resolve.extensions.prepend('.svelte').prepend(`.${platform}.svelte`);
+
+	// add a rule for .svelte files
+	config.module
+		.rule('svelte')
+		.test(/\.svelte$/)
+		.use('svelte-loader-hot')
+		.loader('svelte-loader-hot')
+		.tap((options) => {
+			return {
+				...options,
+				dev: production,
+				preprocess: [getSvelteConfig()?.preprocess, svelteNativePreprocessor()],
+				hotReload: production,
+				hotOptions: {
+					injectCss: false,
+					native: true,
+				},
+			};
+		})
+		.end();
+
+	// set up ts support in svelte files
+	config.module
+		.rule('ts')
+		.use('ts-loader')
+		.loader('ts-loader')
+		.tap((options = {}) => {
+			return merge(options, {
+				appendTsSuffixTo: ['\\.svelte$'],
+			});
+		});
+
+	// add an alias for svelte, since some plugins may try to import it
+	config.resolve.alias.set('svelte', 'svelte-native');
+
 	return config;
 }
+
+function getSvelteConfig(): { preprocess: any } | null {
+	try {
+		const resolvedPath = require.resolve(`./svelte.config.js`, {
+			paths: [getProjectRootPath()],
+		});
+		return require(resolvedPath);
+	} catch (e) {
+		return null;
+	}
+}