fix: optimize serving static files

Optimize serving static files

packages/rest/src/rest.server.ts

@@ -33,6 +33,7 @@ import {
   Route,
   RouteEntry,
   RoutingTable,
+  StaticRoute,
 } from './router/routing-table';
 
 import {DefaultSequence, SequenceFunction, SequenceHandler} from './sequence';
@@ -46,6 +47,7 @@ import {
   Send,
 } from './types';
 import {ServerOptions} from 'https';
+import * as HttpErrors from 'http-errors';
 
 const debug = require('debug')('loopback:rest:server');
 
@@ -190,6 +192,25 @@ export class RestServer extends Context implements Server, HttpServerLike {
     this._setupRequestHandler();
 
     this.bind(RestBindings.HANDLER).toDynamicValue(() => this.httpHandler);
+
+    // LB4's static assets serving router
+    const staticAssetsRouter = new StaticRoute(
+      (req: Request, res: Response) => {
+        return new Promise((resolve, reject) => {
+          const onFinished = () => resolve();
+          res.once('finish', onFinished);
+          this._routerForStaticAssets.handle(req, res, (err: Error) => {
+            if (err) {
+              return reject(err);
+            }
+            // Express router called next, which means no route was matched
+            return reject(new HttpErrors.NotFound());
+          });
+        });
+      },
+    );
+
+    this.httpHandler.registerRoute(staticAssetsRouter);
   }
 
   protected _setupRequestHandler() {
@@ -243,7 +264,6 @@ export class RestServer extends Context implements Server, HttpServerLike {
   protected _setupRouterForStaticAssets() {
     if (!this._routerForStaticAssets) {
       this._routerForStaticAssets = express.Router();
-      this._expressApp.use(this._routerForStaticAssets);
     }
   }
 
@@ -597,12 +617,6 @@ export class RestServer extends Context implements Server, HttpServerLike {
    * @param options Options for serve-static
    */
   static(path: PathParams, rootDir: string, options?: ServeStaticOptions) {
-    const re = pathToRegExp(path, [], {end: false});
-    if (re.test('/')) {
-      throw new Error(
-        'Static assets cannot be mount to "/" to avoid performance penalty.',
-      );
-    }
     this._routerForStaticAssets.use(path, express.static(rootDir, options));
   }
 

packages/rest/src/router/router-base.ts

@@ -49,6 +49,11 @@ export abstract class BaseRouter implements RestRouter {
     else return this.findRouteWithPathVars(request);
   }
 
+  getStaticAssetsRouter() {
+    const route = this.routesWithoutPathVars['/get/*'];
+    return createResolvedRoute(route, {});
+  }
+
   list() {
     let routes = Object.values(this.routesWithoutPathVars);
     routes = routes.concat(this.listRoutesWithPathVars());

packages/rest/src/router/routing-table.ts

@@ -27,6 +27,8 @@ import {
   OperationRetval,
 } from '../types';
 
+import {RestBindings} from '../keys';
+
 import {ControllerSpec} from '@loopback/openapi-v3';
 
 import * as assert from 'assert';
@@ -72,6 +74,8 @@ export interface RestRouter {
    */
   find(request: Request): ResolvedRoute | undefined;
 
+  getStaticAssetsRouter(): ResolvedRoute;
+
   /**
    * List all routes
    */
@@ -180,10 +184,8 @@ export class RoutingTable {
       return found;
     }
 
-    debug('No route found for %s %s', request.method, request.path);
-    throw new HttpErrors.NotFound(
-      `Endpoint "${request.method} ${request.path}" not found.`,
-    );
+    const staticAssetsRouter = this._router.getStaticAssetsRouter();
+    return staticAssetsRouter;
   }
 }
 
@@ -238,6 +240,31 @@ export interface ResolvedRoute extends RouteEntry {
   readonly schemas: SchemasObject;
 }
 
+export class StaticRoute implements RouteEntry {
+  public readonly verb: string = 'get';
+  public readonly path: string = '*';
+  public readonly spec: OperationObject = {responses: {}};
+
+  constructor(private _handler: Function) {}
+
+  updateBindings(requestContext: Context): void {
+    // no-op
+  }
+
+  async invokeHandler(
+    requestContext: Context,
+    args: OperationArgs,
+  ): Promise<OperationRetval> {
+    const req = await requestContext.get(RestBindings.Http.REQUEST);
+    const res = await requestContext.get(RestBindings.Http.RESPONSE);
+    return this._handler(req, res);
+  }
+
+  describe(): string {
+    return 'final route to handle static assets';
+  }
+}
+
 /**
  * Base implementation of RouteEntry
  */
@@ -290,7 +317,7 @@ export class Route extends BaseRoute {
     verb: string,
     path: string,
     public readonly spec: OperationObject,
-    protected readonly _handler: Function,
+    protected readonly _handler: Function, // <-- doesn't this Function have a signature?
   ) {
     super(verb, path, spec);
   }