feat: allow adapters to pass in Vite plugins

.changeset/lazy-tools-bathe.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': major
+---
+
+feat: allow adapters to provide additional Vite plugins

documentation/docs/25-build-and-deploy/99-writing-adapters.md

@@ -39,14 +39,19 @@ export default function (options) {
 				// Return `true` if this adapter supports loading `instrumentation.server.js`.
 				// Return `false if it can't, or throw a descriptive error.
 			}
+		},
+		vite: {
+			plugins: [
+				// add plugins here to integrate with Vite
+			]
 		}
 	};
 
 	return adapter;
 }
 ```
 
-Of these, `name` and `adapt` are required. `emulate` and `supports` are optional.
+Of these, `name` and `adapt` are required. `emulate`, `vite.plugins` and `supports` are optional.
 
 Within the `adapt` method, there are a number of things that an adapter should do:
 

packages/kit/src/exports/public.d.ts

@@ -23,6 +23,7 @@ import {
 import { BuildData, SSRNodeLoader, SSRRoute, ValidatedConfig } from 'types';
 import { SvelteConfig } from '@sveltejs/vite-plugin-svelte';
 import { StandardSchemaV1 } from '@standard-schema/spec';
+import { Plugin } from 'vite';
 import {
 	RouteId as AppRouteId,
 	LayoutParams as AppLayoutParams,
@@ -68,6 +69,13 @@ export interface Adapter {
 	 * during dev, build and prerendering.
 	 */
 	emulate?: () => MaybePromise<Emulator>;
+	vite?: {
+		/**
+		 * Plugins provided by the adapter are placed before any of SvelteKit's own plugins.
+		 * @since 3.0.0
+		 */
+		plugins?: Plugin[];
+	};
 }
 
 export type LoadProperties<input extends Record<string, any> | void> = input extends void

packages/kit/src/exports/vite/index.js

@@ -1171,6 +1171,9 @@ function kit({ svelte_config }) {
 		}
 	};
 
+	/** @type {() => Promise<void> | undefined} */
+	let finalise;
+
 	/** @type {Plugin} */
 	const plugin_compile = {
 		name: 'vite-plugin-sveltekit-compile',
@@ -1773,63 +1776,87 @@ function kit({ svelte_config }) {
 				})};\n`
 			);
 
-			if (service_worker_entry_file) {
-				log.info('Building service worker');
-
-				// mirror client settings that we couldn't set per environment in the config hook
-				builder.environments.serviceWorker.config.define =
-					builder.environments.client.config.define;
-				builder.environments.serviceWorker.config.resolve.alias = [
-					...get_config_aliases(kit, vite_config.root)
-				];
+			// defer the adapt step to run after any buildApp hooks the adapter might have
+			finalise = async () => {
+				// defer creating the service worker too because other plugins might build
+				// the client environment again and overwrite our service worker which
+				// outputs to the same directory
+				if (service_worker_entry_file) {
+					log.info('Building service worker');
+
+					// mirror client settings that we couldn't set per environment in the config hook
+					builder.environments.serviceWorker.config.define =
+						builder.environments.client.config.define;
+					builder.environments.serviceWorker.config.resolve.alias = [
+						...get_config_aliases(kit, vite_config.root)
+					];
 
-				// we have to overwrite this because it can't be configured per environment in the config hook
-				builder.environments.serviceWorker.config.experimental.renderBuiltUrl = (filename) => {
-					return {
-						runtime: `new URL(${JSON.stringify(filename)}, location.href).pathname`
+					// we have to overwrite this because it can't be configured per environment in the config hook
+					builder.environments.serviceWorker.config.experimental.renderBuiltUrl = (filename) => {
+						return {
+							runtime: `new URL(${JSON.stringify(filename)}, location.href).pathname`
+						};
 					};
-				};
-
-				await builder.build(builder.environments.serviceWorker);
-			}
 
-			console.log(
-				`\nRun ${styleText(['bold', 'cyan'], 'npm run preview')} to preview your production build locally.`
-			);
-
-			if (kit.adapter) {
-				const { adapt } = await import('../../core/adapt/index.js');
-				await adapt(
-					svelte_config,
-					build_data,
-					metadata,
-					prerendered,
-					prerender_results.prerender_map,
-					log,
-					remotes,
-					vite_config,
-					explicit_env_config
-				);
-			} else {
-				console.log(styleText(['bold', 'yellow'], '\nNo adapter specified'));
+					await builder.build(builder.environments.serviceWorker);
+				}
 
-				const link = styleText(['bold', 'cyan'], 'https://svelte.dev/docs/kit/adapters');
 				console.log(
-					`See ${link} to learn how to configure your app to run on the platform of your choosing`
+					`\nRun ${styleText(['bold', 'cyan'], 'npm run preview')} to preview your production build locally.`
 				);
+
+				if (kit.adapter) {
+					const { adapt } = await import('../../core/adapt/index.js');
+					await adapt(
+						svelte_config,
+						build_data,
+						metadata,
+						prerendered,
+						prerender_results.prerender_map,
+						log,
+						remotes,
+						vite_config,
+						explicit_env_config
+					);
+				} else {
+					console.log(styleText(['bold', 'yellow'], '\nNo adapter specified'));
+
+					const link = styleText(['bold', 'cyan'], 'https://svelte.dev/docs/kit/adapters');
+					console.log(
+						`See ${link} to learn how to configure your app to run on the platform of your choosing`
+					);
+				}
+			};
+		}
+	};
+
+	/** @type {Plugin} */
+	const plugin_adapter = {
+		name: 'vite-plugin-sveltekit-adapter',
+		apply: 'build',
+		buildApp: {
+			// this will run after any buildApp hooks provided by other Vite plugins
+			// see https://vite.dev/guide/api-environment-frameworks#environments-during-build
+			order: 'post',
+			async handler() {
+				await finalise?.();
 			}
 		}
 	};
 
-	return [
-		plugin_setup,
-		plugin_remote,
-		plugin_virtual_modules,
-		process.env.TEST !== 'true' ? plugin_guard : undefined,
-		service_worker_entry_file && plugin_service_worker_env,
-		plugin_service_worker,
-		plugin_compile
-	].filter((p) => !!p);
+	return /** @type {Plugin[]} */ (
+		[
+			svelte_config.kit.adapter?.vite?.plugins,
+			plugin_setup,
+			plugin_remote,
+			plugin_virtual_modules,
+			process.env.TEST !== 'true' ? plugin_guard : undefined,
+			service_worker_entry_file ? plugin_service_worker_env : undefined,
+			plugin_service_worker,
+			plugin_compile,
+			plugin_adapter
+		].filter(Boolean)
+	);
 }
 
 /**

packages/kit/types/index.d.ts

@@ -4,6 +4,7 @@
 declare module '@sveltejs/kit' {
 	import type { SvelteConfig } from '@sveltejs/vite-plugin-svelte';
 	import type { StandardSchemaV1 } from '@standard-schema/spec';
+	import type { Plugin } from 'vite';
 	import type { RouteId as AppRouteId, LayoutParams as AppLayoutParams, ResolvedPathname } from '$app/types';
 	// @ts-ignore this is an optional peer dependency so could be missing. Written like this so dts-buddy preserves the ts-ignore
 	type Span = import('@opentelemetry/api').Span;
@@ -42,6 +43,13 @@ declare module '@sveltejs/kit' {
 		 * during dev, build and prerendering.
 		 */
 		emulate?: () => MaybePromise<Emulator>;
+		vite?: {
+			/**
+			 * Plugins provided by the adapter are placed before any of SvelteKit's own plugins.
+			 * @since 3.0.0
+			 */
+			plugins?: Plugin[];
+		};
 	}
 
 	export type LoadProperties<input extends Record<string, any> | void> = input extends void