refactor: Separate middleware from Express.

config/config-default.json

@@ -12,6 +12,7 @@
     "files-scs:config/presets/ldp/request-parser.json",
     "files-scs:config/presets/ldp/websockets.json",
     "files-scs:config/presets/logging.json",
+    "files-scs:config/presets/middleware.json",
     "files-scs:config/presets/representation-conversion.json",
     "files-scs:config/presets/setup.json",
     "files-scs:config/presets/storage/backend/storage-memory.json",

config/config-file.json

@@ -12,6 +12,7 @@
     "files-scs:config/presets/ldp/request-parser.json",
     "files-scs:config/presets/ldp/websockets.json",
     "files-scs:config/presets/logging.json",
+    "files-scs:config/presets/middleware.json",
     "files-scs:config/presets/representation-conversion.json",
     "files-scs:config/presets/setup.json",
     "files-scs:config/presets/storage/backend/storage-filesystem.json",

config/config-path-routing.json

@@ -12,6 +12,7 @@
     "files-scs:config/presets/ldp/request-parser.json",
     "files-scs:config/presets/ldp/websockets.json",
     "files-scs:config/presets/logging.json",
+    "files-scs:config/presets/middleware.json",
     "files-scs:config/presets/representation-conversion.json",
     "files-scs:config/presets/setup.json",
     "files-scs:config/presets/storage/backend/storage-filesystem.json",

config/config-rdf-to-sparql-endpoint.json

@@ -12,6 +12,7 @@
     "files-scs:config/presets/ldp/request-parser.json",
     "files-scs:config/presets/ldp/websockets.json",
     "files-scs:config/presets/logging.json",
+    "files-scs:config/presets/middleware.json",
     "files-scs:config/presets/representation-conversion.json",
     "files-scs:config/presets/setup.json",
     "files-scs:config/presets/storage/backend/storage-filesystem.json",

config/config-sparql-endpoint.json

@@ -12,6 +12,7 @@
     "files-scs:config/presets/ldp/request-parser.json",
     "files-scs:config/presets/ldp/websockets.json",
     "files-scs:config/presets/logging.json",
+    "files-scs:config/presets/middleware.json",
     "files-scs:config/presets/representation-conversion.json",
     "files-scs:config/presets/setup.json",
     "files-scs:config/presets/storage/backend/storage-sparql-endpoint.json",

config/presets/http.json

@@ -17,6 +17,18 @@
       "ExpressHttpServerFactory:_handler": {
         "@id": "urn:solid-server:default:HttpHandler"
       }
+    },
+    {
+      "@id": "urn:solid-server:default:HttpHandler",
+      "@type": "AllVoidCompositeHandler",
+      "AllVoidCompositeHandler:_handlers": [
+        {
+          "@id": "urn:solid-server:default:Middleware"
+        },
+        {
+          "@id": "urn:solid-server:default:LdpHandler"
+        }
+      ]
     }
   ]
 }

config/presets/ldp.json

@@ -2,7 +2,7 @@
   "@context": "https://linkedsoftwaredependencies.org/bundles/npm/@solid/community-server/^1.0.0/components/context.jsonld",
   "@graph": [
     {
-      "@id": "urn:solid-server:default:HttpHandler",
+      "@id": "urn:solid-server:default:LdpHandler",
       "@type": "AuthenticatedLdpHandler",
       "AuthenticatedLdpHandler:_args_requestParser": {
         "@id": "urn:solid-server:default:RequestParser"

config/presets/middleware.json

@@ -0,0 +1,17 @@
+{
+  "@context": "https://linkedsoftwaredependencies.org/bundles/npm/@solid/community-server/^1.0.0/components/context.jsonld",
+  "@graph": [
+    {
+      "@id": "urn:solid-server:default:Middleware",
+      "@type": "AllVoidCompositeHandler",
+      "AllVoidCompositeHandler:_handlers": [
+        {
+          "@type": "CorsHandler"
+        },
+        {
+          "@type": "HeaderHandler"
+        }
+      ]
+    }
+  ]
+}

index.ts

@@ -95,6 +95,10 @@ export * from './src/server/HttpResponse';
 export * from './src/server/WebSocketServerFactory';
 export * from './src/server/WebSocketHandler';
 
+// Server/Middleware
+export * from './src/server/middleware/CorsHandler';
+export * from './src/server/middleware/HeaderHandler';
+
 // Storage/Accessors
 export * from './src/storage/accessors/DataAccessor';
 export * from './src/storage/accessors/FileDataAccessor';

src/server/ExpressHttpServerFactory.ts

@@ -1,5 +1,4 @@
 import type { Server } from 'http';
-import cors from 'cors';
 import type { Express } from 'express';
 import express from 'express';
 import { getLoggerFor } from '../logging/LogUtil';
@@ -17,28 +16,11 @@ export class ExpressHttpServerFactory implements HttpServerFactory {
   }
 
   public startServer(port: number): Server {
-    const app = express();
-    this.setup(app);
-    return app.listen(port);
+    return this.createApp().listen(port);
   }
 
-  protected setup(app: Express): void {
-    // Set up server identification
-    app.use((request, response, done): void => {
-      response.setHeader('X-Powered-By', 'Community Solid Server');
-      done();
-    });
-
-    // Set up Cross-Origin Resource Sharing (CORS)
-    app.use(cors({
-      // Based on https://github.com/solid/solid-spec/blob/master/recommendations-server.md#cors---cross-origin-resource-sharing
-      // By default origin is always '*', this forces it to be the origin header if there is one
-      origin: (origin, callback): void => callback(null, (origin ?? '*') as any),
-      methods: [ 'GET', 'HEAD', 'OPTIONS', 'POST', 'PUT', 'PATCH', 'DELETE' ],
-    }));
-
-    // Delegate to the main handler
-    app.use(async(request, response, done): Promise<void> => {
+  protected createApp(): Express {
+    return express().use(async(request, response, done): Promise<void> => {
       try {
         this.logger.info(`Received request for ${request.url}`);
         await this.handler.handleSafe({ request: guardStream(request), response });

src/server/middleware/CorsHandler.ts

@@ -0,0 +1,26 @@
+import cors from 'cors';
+import type { RequestHandler } from 'express';
+import { HttpHandler } from '../HttpHandler';
+import type { HttpRequest } from '../HttpRequest';
+import type { HttpResponse } from '../HttpResponse';
+
+/**
+ * Handler that sets CORS options on the response.
+ */
+export class CorsHandler extends HttpHandler {
+  private readonly corsHandler: RequestHandler;
+
+  public constructor() {
+    super();
+    this.corsHandler = cors({
+      origin: (origin, callback): void => callback(null, (origin ?? '*') as any),
+      methods: [ 'GET', 'HEAD', 'OPTIONS', 'POST', 'PUT', 'PATCH', 'DELETE' ],
+    });
+  }
+
+  public async handle(input: { request: HttpRequest; response: HttpResponse }): Promise<void> {
+    return new Promise((resolve): void => {
+      this.corsHandler(input.request as any, input.response as any, (): void => resolve());
+    });
+  }
+}

src/server/middleware/HeaderHandler.ts

@@ -0,0 +1,22 @@
+import { HttpHandler } from '../HttpHandler';
+import type { HttpResponse } from '../HttpResponse';
+
+/**
+ * Handler that sets custom headers on the response.
+ */
+export class HeaderHandler extends HttpHandler {
+  private readonly headers: Record<string, string>;
+
+  public constructor() {
+    super();
+    this.headers = {
+      'x-powered-by': 'Community Solid Server',
+    };
+  }
+
+  public async handle({ response }: { response: HttpResponse }): Promise<void> {
+    for (const header of Object.keys(this.headers)) {
+      response.setHeader(header, this.headers[header]);
+    }
+  }
+}

test/configs/middleware.json

@@ -0,0 +1,13 @@
+{
+  "@context": "https://linkedsoftwaredependencies.org/bundles/npm/@solid/community-server/^1.0.0/components/context.jsonld",
+  "import": [
+    "files-scs:config/presets/http.json",
+    "files-scs:config/presets/middleware.json"
+  ],
+  "@graph": [
+    {
+      "@id": "urn:solid-server:default:LdpHandler",
+      "@type": "Variable"
+    }
+  ]
+}

test/configs/websockets.json

@@ -9,6 +9,7 @@
     "files-scs:config/presets/ldp/response-writer.json",
     "files-scs:config/presets/ldp/request-parser.json",
     "files-scs:config/presets/ldp/websockets.json",
+    "files-scs:config/presets/middleware.json",
     "files-scs:config/presets/representation-conversion.json",
     "files-scs:config/presets/storage/backend/storage-memory.json",
     "files-scs:config/presets/storage/routing/no-routing.json",
@@ -17,7 +18,7 @@
   ],
   "@graph": [
     {
-      "@id": "urn:solid-server:default:HttpHandler",
+      "@id": "urn:solid-server:default:LdpHandler",
       "@type": "AuthenticatedLdpHandler",
       "AuthenticatedLdpHandler:_args_requestParser": {
         "@id": "urn:solid-server:default:RequestParser"

test/integration/Middleware.test.ts

@@ -0,0 +1,69 @@
+import type { Server } from 'http';
+import request from 'supertest';
+import type { ExpressHttpServerFactory } from '../../src/server/ExpressHttpServerFactory';
+import { HttpHandler } from '../../src/server/HttpHandler';
+import type { HttpRequest } from '../../src/server/HttpRequest';
+import type { HttpResponse } from '../../src/server/HttpResponse';
+import { instantiateFromConfig } from '../configs/Util';
+
+const port = 6002;
+
+class SimpleHttpHandler extends HttpHandler {
+  public async handle(input: { request: HttpRequest; response: HttpResponse }): Promise<void> {
+    input.response.writeHead(200);
+    input.response.end('Hello World');
+  }
+}
+
+describe('An Express server with middleware', (): void => {
+  let server: Server;
+
+  beforeAll(async(): Promise<void> => {
+    const factory = await instantiateFromConfig(
+      'urn:solid-server:default:ExpressHttpServerFactory', 'middleware.json', {
+        'urn:solid-server:default:LdpHandler': new SimpleHttpHandler(),
+      },
+    ) as ExpressHttpServerFactory;
+    server = factory.startServer(port);
+  });
+
+  afterEach(async(): Promise<void> => {
+    server.close();
+  });
+
+  it('sends server identification in the X-Powered-By header.', async(): Promise<void> => {
+    const res = await request(server).get('/');
+    expect(res.header).toEqual(expect.objectContaining({
+      'x-powered-by': 'Community Solid Server',
+    }));
+  });
+
+  it('returns CORS headers for an OPTIONS request.', async(): Promise<void> => {
+    const res = await request(server)
+      .options('/')
+      .set('Access-Control-Request-Headers', 'content-type')
+      .set('Access-Control-Request-Method', 'POST')
+      .set('Host', 'test.com')
+      .expect(204);
+    expect(res.header).toEqual(expect.objectContaining({
+      'access-control-allow-origin': '*',
+      'access-control-allow-headers': 'content-type',
+    }));
+    const corsMethods = res.header['access-control-allow-methods'].split(',')
+      .map((method: string): string => method.trim());
+    const allowedMethods = [ 'GET', 'HEAD', 'OPTIONS', 'POST', 'PUT', 'PATCH', 'DELETE' ];
+    expect(corsMethods).toEqual(expect.arrayContaining(allowedMethods));
+    expect(corsMethods).toHaveLength(allowedMethods.length);
+  });
+
+  it('specifies CORS origin header if an origin was supplied.', async(): Promise<void> => {
+    const res = await request(server).get('/').set('origin', 'test.com').expect(200);
+    expect(res.header).toEqual(expect.objectContaining({ 'access-control-allow-origin': 'test.com' }));
+  });
+
+  it('sends incoming requests to the handler.', async(): Promise<void> => {
+    const response = request(server).get('/').set('Host', 'test.com');
+    expect(response).toBeDefined();
+    await response.expect(200).expect('Hello World');
+  });
+});

test/unit/server/ExpressHttpServerFactory.test.ts

@@ -42,7 +42,6 @@ describe('ExpressHttpServerFactory', (): void => {
   });
 
   afterEach(async(): Promise<void> => {
-    // Close server
     server.close();
   });
 
@@ -50,36 +49,6 @@ describe('ExpressHttpServerFactory', (): void => {
     mock.mockReset();
   });
 
-  it('sends server identification in the X-Powered-By header.', async(): Promise<void> => {
-    const res = await request(server).get('/');
-    expect(res.header).toEqual(expect.objectContaining({
-      'x-powered-by': 'Community Solid Server',
-    }));
-  });
-
-  it('returns CORS headers for an OPTIONS request.', async(): Promise<void> => {
-    const res = await request(server)
-      .options('/')
-      .set('Access-Control-Request-Headers', 'content-type')
-      .set('Access-Control-Request-Method', 'POST')
-      .set('Host', 'test.com')
-      .expect(204);
-    expect(res.header).toEqual(expect.objectContaining({
-      'access-control-allow-origin': '*',
-      'access-control-allow-headers': 'content-type',
-    }));
-    const corsMethods = res.header['access-control-allow-methods'].split(',')
-      .map((method: string): string => method.trim());
-    const allowedMethods = [ 'GET', 'HEAD', 'OPTIONS', 'POST', 'PUT', 'PATCH', 'DELETE' ];
-    expect(corsMethods).toEqual(expect.arrayContaining(allowedMethods));
-    expect(corsMethods).toHaveLength(allowedMethods.length);
-  });
-
-  it('specifies CORS origin header if an origin was supplied.', async(): Promise<void> => {
-    const res = await request(server).get('/').set('origin', 'test.com').expect(200);
-    expect(res.header).toEqual(expect.objectContaining({ 'access-control-allow-origin': 'test.com' }));
-  });
-
   it('sends incoming requests to the handler.', async(): Promise<void> => {
     await request(server).get('/').set('Host', 'test.com').expect(200);
     expect(canHandleJest).toHaveBeenCalledTimes(1);

test/unit/server/middleware/CorsHandler.test.ts

@@ -0,0 +1,33 @@
+import { createRequest, createResponse } from 'node-mocks-http';
+import { CorsHandler } from '../../../../src/server/middleware/CorsHandler';
+import { guardStream } from '../../../../src/util/GuardedStream';
+
+describe('a CorsHandler', (): void => {
+  let handler: CorsHandler;
+
+  beforeAll(async(): Promise<void> => {
+    handler = new CorsHandler();
+  });
+
+  it('returns CORS headers.', async(): Promise<void> => {
+    const request = guardStream(createRequest());
+    const response = createResponse();
+    await handler.handleSafe({ request, response });
+    expect(response.getHeaders()).toEqual(expect.objectContaining({
+      'access-control-allow-origin': '*',
+    }));
+  });
+
+  it('echoes the origin when specified.', async(): Promise<void> => {
+    const request = guardStream(createRequest({
+      headers: {
+        origin: 'example.org',
+      },
+    }));
+    const response = createResponse();
+    await handler.handleSafe({ request, response });
+    expect(response.getHeaders()).toEqual(expect.objectContaining({
+      'access-control-allow-origin': 'example.org',
+    }));
+  });
+});

test/unit/server/middleware/HeaderHandler.test.ts

@@ -0,0 +1,20 @@
+import { createRequest, createResponse } from 'node-mocks-http';
+import { HeaderHandler } from '../../../../src/server/middleware/HeaderHandler';
+import { guardStream } from '../../../../src/util/GuardedStream';
+
+describe('a HeaderHandler', (): void => {
+  let handler: HeaderHandler;
+
+  beforeAll(async(): Promise<void> => {
+    handler = new HeaderHandler();
+  });
+
+  it('returns an X-Powered-By header.', async(): Promise<void> => {
+    const request = guardStream(createRequest());
+    const response = createResponse();
+    await handler.handleSafe({ request, response });
+    expect(response.getHeaders()).toEqual(expect.objectContaining({
+      'x-powered-by': 'Community Solid Server',
+    }));
+  });
+});