fix: use virtual import for storage drivers (#12520)

* fix: use virtual import for storage drivers

* Don't try to resolve anythign in build

* Fix test

* Polyfill node:url

* Handle custom drivers directly

* No need for path

* Update packages/astro/src/core/session.ts

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

---------

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

packages/astro/src/core/create-vite.ts

@@ -33,6 +33,7 @@ import markdownVitePlugin from '../vite-plugin-markdown/index.js';
 import astroScannerPlugin from '../vite-plugin-scanner/index.js';
 import astroScriptsPlugin from '../vite-plugin-scripts/index.js';
 import astroScriptsPageSSRPlugin from '../vite-plugin-scripts/page-ssr.js';
+import vitePluginSessions from '../vite-plugin-sessions/index.js';
 import { vitePluginSSRManifest } from '../vite-plugin-ssr-manifest/index.js';
 import type { SSRManifest } from './app/types.js';
 import type { Logger } from './logger/core.js';
@@ -143,6 +144,7 @@ export async function createVite(
 			astroLoadFallbackPlugin({ fs, root: settings.config.root }),
 			astroVitePlugin({ settings, logger }),
 			astroScriptsPlugin({ settings }),
+			vitePluginSessions({ settings }),
 			// The server plugin is for dev only and having it run during the build causes
 			// the build to run very slow as the filewatcher is triggered often.
 			command === 'dev' && vitePluginAstroServer({ settings, logger, fs, manifest, ssrManifest }), // ssrManifest is only required in dev mode, where it gets created before a Vite instance is created, and get passed to this function

packages/astro/src/core/session.ts

@@ -344,7 +344,7 @@ export class AstroSession<TDriver extends SessionDriverName = any> {
 	 * Ensures the storage is initialized.
 	 * This is called automatically when a storage operation is needed.
 	 */
-	async #ensureStorage():Promise<Storage> {
+	async #ensureStorage(): Promise<Storage> {
 		if (this.#storage) {
 			return this.#storage;
 		}
@@ -363,13 +363,22 @@ export class AstroSession<TDriver extends SessionDriverName = any> {
 		}
 
 		let driver: ((config: SessionConfig<TDriver>['options']) => Driver) | null = null;
-		const entry =
-			builtinDrivers[this.#config.driver as keyof typeof builtinDrivers] || this.#config.driver;
-		try {
+		const isBuiltin = this.#config.driver in builtinDrivers;
 		// Try to load the driver from the built-in unstorage drivers.
 		// Otherwise, assume it's a custom driver and load by name.
+		const driverPackage: string = isBuiltin
+			? builtinDrivers[this.#config.driver as keyof typeof builtinDrivers]
+			: this.#config.driver;
 
-			driver = await import(entry).then((r) => r.default || r);
+		try {
+			// If driver is not a builtin, or in development or test, load the driver directly.
+			if (!isBuiltin || process.env.NODE_ENV === 'development' || process.env.NODE_TEST_CONTEXT) {
+				driver = await import(/* @vite-ignore */ driverPackage).then((r) => r.default || r);
+			} else {
+				// In production, load via the virtual module as it will be bundled by Vite
+				// @ts-expect-error - virtual module
+				driver = await import('@astro-session-driver').then((r) => r.default || r);
+			}
 		} catch (err: any) {
 			// If the driver failed to load, throw an error.
 			if (err.code === 'ERR_MODULE_NOT_FOUND') {
@@ -377,7 +386,7 @@ export class AstroSession<TDriver extends SessionDriverName = any> {
 					{
 						...SessionStorageInitError,
 						message: SessionStorageInitError.message(
-							err.message.includes(`Cannot find package '${entry}'`)
+							err.message.includes(`Cannot find package '${driverPackage}'`)
 								? 'The driver module could not be found.'
 								: err.message,
 							this.#config.driver,

packages/astro/src/vite-plugin-sessions/index.ts

@@ -0,0 +1,43 @@
+import { fileURLToPath } from 'node:url';
+import { builtinDrivers } from 'unstorage';
+import type { Plugin as VitePlugin } from 'vite';
+import type { AstroSettings } from '../types/astro.js';
+
+const SESSION_DRIVER_ID = '@astro-session-driver';
+const RESOLVED_SESSION_DRIVER_ID = `\0${SESSION_DRIVER_ID}`;
+
+export default function vitePluginSessions({ settings }: { settings: AstroSettings }): VitePlugin {
+	return {
+		name: 'astro:vite-plugin-sessions',
+		enforce: 'pre',
+		async resolveId(source) {
+			if (source === SESSION_DRIVER_ID) {
+				return RESOLVED_SESSION_DRIVER_ID;
+			}
+			// Resolve the driver entrypoint so that we bundle it
+			if (source.startsWith('unstorage/drivers/')) {
+				return fileURLToPath(import.meta.resolve(source));
+			}
+		},
+		async load(id) {
+			if (id === RESOLVED_SESSION_DRIVER_ID) {
+				let driver = settings.config.experimental?.session?.driver;
+				if (driver && driver in builtinDrivers) {
+					if (driver === 'fs') {
+						// fs tries to bundle chokidar (and therefore fsevents), which is a binary
+						driver = 'fsLite';
+					}
+					driver = builtinDrivers[driver as keyof typeof builtinDrivers];
+				}
+				if (!driver) {
+					return `export default function driver() { return null }`;
+				}
+				const resolved = await this.resolve(driver, undefined, { skipSelf: false });
+				if (!resolved) {
+					throw new Error(`Could not resolve session driver ${driver}`);
+				}
+				return `export { default } from ${JSON.stringify(resolved?.id)};`;
+			}
+		},
+	};
+}

packages/astro/test/fixtures/sessions/astro.config.mjs

@@ -9,7 +9,7 @@ export default defineConfig({
 	output: 'server',
 	experimental: {
 		session: {
-			driver: 'fs',
+			driver: 'fsLite',
 			options: {
 				base: join(tmpdir(), 'sessions'),
 			},