refactor(rest): rework StaticAssetsRoute into ExternalExpressRoutes

packages/rest/src/rest.server.ts

@@ -41,7 +41,7 @@ import {
   Route,
   RouteEntry,
   RoutingTable,
-  StaticAssetsRoute,
+  ExternalExpressRoutes,
   RedirectRoute,
 } from './router';
 import {DefaultSequence, SequenceFunction, SequenceHandler} from './sequence';
@@ -298,7 +298,7 @@ export class RestServer extends Context implements Server, HttpServerLike {
      * Check if there is custom router in the context
      */
     const router = this.getSync(RestBindings.ROUTER, {optional: true});
-    const routingTable = new RoutingTable(router, this._staticAssetRoute);
+    const routingTable = new RoutingTable(router, this._externalRoutes);
 
     this._httpHandler = new HttpHandler(this, routingTable);
     for (const b of this.find('controllers.*')) {
@@ -691,8 +691,10 @@ export class RestServer extends Context implements Server, HttpServerLike {
     );
   }
 
-  // The route for static assets
-  private _staticAssetRoute = new StaticAssetsRoute();
+  /*
+   * Registry of external routes & static assets
+   */
+  private _externalRoutes = new ExternalExpressRoutes();
 
   /**
    * Mount static assets to the REST server.
@@ -703,7 +705,7 @@ export class RestServer extends Context implements Server, HttpServerLike {
    * @param options Options for serve-static
    */
   static(path: PathParams, rootDir: string, options?: ServeStaticOptions) {
-    this._staticAssetRoute.registerAssets(path, rootDir, options);
+    this._externalRoutes.registerAssets(path, rootDir, options);
   }
 
   /**

packages/rest/src/router/static-assets-route.ts → packages/rest/src/router/external-express-routes.ts

@@ -5,7 +5,8 @@
 
 import {Context} from '@loopback/context';
 import {OperationObject, SchemasObject} from '@loopback/openapi-v3-types';
-import {RequestHandler, Router, static as serveStatic} from 'express';
+import * as express from 'express';
+import {RequestHandler} from 'express';
 import {PathParams} from 'express-serve-static-core';
 import * as HttpErrors from 'http-errors';
 import * as onFinished from 'on-finished';
@@ -21,30 +22,47 @@ import {
 } from '../types';
 import {ResolvedRoute, RouteEntry} from './route-entry';
 
-export class StaticAssetsRoute implements RouteEntry, ResolvedRoute {
-  // ResolvedRoute API
-  readonly pathParams: PathParameterValues = [];
-  readonly schemas: SchemasObject = {};
+export type ExpressRequestHandler = express.RequestHandler;
 
-  // RouteEntry implementation
-  readonly verb: string = 'get';
-  readonly path: string = '/*';
-  readonly spec: OperationObject = {
-    description: 'LoopBack static assets route',
-    'x-visibility': 'undocumented',
-    responses: {},
-  };
-
-  constructor(private readonly _expressRouter: Router = Router()) {}
+/**
+ * A registry of external, Express-style routes. These routes are invoked
+ * _after_ no LB4 route (controller or handler based) matched the incoming
+ * request.
+ *
+ * @private
+ */
+export class ExternalExpressRoutes {
+  protected _staticRoutes: express.Router = express.Router();
 
   public registerAssets(
     path: PathParams,
     rootDir: string,
     options?: ServeStaticOptions,
   ) {
-    this._expressRouter.use(path, serveStatic(rootDir, options));
+    this._staticRoutes.use(path, express.static(rootDir, options));
   }
 
+  find(request: Request): ResolvedRoute {
+    return new ExternalRoute(this._staticRoutes, request.method, request.url, {
+      description: 'LoopBack static assets route',
+      'x-visibility': 'undocumented',
+      responses: {},
+    });
+  }
+}
+
+class ExternalRoute implements RouteEntry, ResolvedRoute {
+  // ResolvedRoute API
+  readonly pathParams: PathParameterValues = [];
+  readonly schemas: SchemasObject = {};
+
+  constructor(
+    private readonly _staticAssets: express.Router,
+    public readonly verb: string,
+    public readonly path: string,
+    public readonly spec: OperationObject,
+  ) {}
+
   updateBindings(requestContext: Context): void {
     // no-op
   }
@@ -54,21 +72,21 @@ export class StaticAssetsRoute implements RouteEntry, ResolvedRoute {
     args: OperationArgs,
   ): Promise<OperationRetval> {
     const handled = await executeRequestHandler(
-      this._expressRouter,
+      this._staticAssets,
       request,
       response,
     );
+    if (handled) return;
 
-    if (!handled) {
-      // Express router called next, which means no route was matched
-      throw new HttpErrors.NotFound(
-        `Endpoint "${request.method} ${request.path}" not found.`,
-      );
-    }
+    // Express router called next, which means no route was matched
+    throw new HttpErrors.NotFound(
+      `Endpoint "${request.method} ${request.path}" not found.`,
+    );
   }
 
   describe(): string {
-    return 'final route to handle static assets';
+    // TODO(bajtos) provide better description for Express routes with spec
+    return `External Express route "${this.verb} ${this.path}"`;
   }
 }
 

packages/rest/src/router/index.ts

@@ -8,7 +8,7 @@ export * from './route-entry';
 export * from './base-route';
 export * from './controller-route';
 export * from './handler-route';
-export * from './static-assets-route';
+export * from './external-express-routes';
 export * from './redirect-route';
 
 // routers

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

@@ -22,7 +22,7 @@ import {
 import {validateApiPath} from './openapi-path';
 import {RestRouter} from './rest-router';
 import {ResolvedRoute, RouteEntry} from './route-entry';
-import {StaticAssetsRoute} from './static-assets-route';
+import {ExternalExpressRoutes} from './external-express-routes';
 import {TrieRouter} from './trie-router';
 
 const debug = debugFactory('loopback:rest:routing-table');
@@ -31,18 +31,10 @@ const debug = debugFactory('loopback:rest:routing-table');
  * Routing table
  */
 export class RoutingTable {
-  /**
-   * A route for static assets
-   */
-  private _staticAssetsRoute: StaticAssetsRoute;
   constructor(
     private readonly _router: RestRouter = new TrieRouter(),
-    staticAssetsRoute?: StaticAssetsRoute,
-  ) {
-    if (staticAssetsRoute) {
-      this._staticAssetsRoute = staticAssetsRoute;
-    }
-  }
+    private _externalRoutes?: ExternalExpressRoutes,
+  ) {}
 
   /**
    * Register a controller as the route
@@ -143,15 +135,14 @@ export class RoutingTable {
       return found;
     }
 
-    // this._staticAssetsRoute will be set only if app.static() was called
-    if (this._staticAssetsRoute) {
+    if (this._externalRoutes) {
       debug(
         'No API route found for %s %s, trying to find a static asset',
         request.method,
         request.path,
       );
 
-      return this._staticAssetsRoute;
+      return this._externalRoutes.find(request);
     }
 
     debug('No route found for %s %s', request.method, request.path);