Merge pull request #32862 from storybookjs/yann/patch-dev-server-preset

Core: Add `experimental_devServer` preset
(cherry picked from commit 6bb3f61)

Author: yannbf

code/core/src/core-server/dev-server.ts

@@ -50,6 +50,9 @@ export async function storybookDevServer(options: Options) {
 
   getMiddleware(options.configDir)(app);
 
+  // Apply experimental_devServer preset to allow addons/frameworks to extend the dev server with middlewares, etc.
+  await options.presets.apply('experimental_devServer', app);
+
   const { port, host, initialPath } = options;
   invariant(port, 'expected options to have a port');
   const proto = options.https ? 'https' : 'http';

code/core/src/types/modules/core-common.ts

@@ -223,7 +223,7 @@ export type Middleware<T extends IncomingMessage = IncomingMessage> = (
   next: (err?: string | Error) => Promise<void> | void
 ) => Promise<void> | void;
 
-interface ServerApp<T extends IncomingMessage = IncomingMessage> {
+export interface ServerApp<T extends IncomingMessage = IncomingMessage> {
   server: NetServer;
 
   use(pattern: RegExp | string, ...handlers: Middleware<T>[]): this;
@@ -476,6 +476,8 @@ export interface StorybookConfigRaw {
 
   experimental_indexers?: Indexer[];
 
+  experimental_devServer?: ServerApp;
+
   docs?: DocsOptions;
 
   previewHead?: string;