feat: Make HeaderHandler customizable.

config/presets/middleware.json

@@ -9,7 +9,13 @@
           "@type": "CorsHandler"
         },
         {
-          "@type": "HeaderHandler"
+          "@type": "HeaderHandler",
+          "HeaderHandler:_headers": [
+            {
+              "HeaderHandler:_headers_key": "X-Powered-By",
+              "HeaderHandler:_headers_value": "Community Solid Server"
+            }
+          ]
         }
       ]
     }

src/server/middleware/HeaderHandler.ts

@@ -7,11 +7,11 @@ import type { HttpResponse } from '../HttpResponse';
 export class HeaderHandler extends HttpHandler {
   private readonly headers: Record<string, string>;
 
-  public constructor() {
+  // Not supported by Components.js yet
+  // eslint-disable-next-line @typescript-eslint/consistent-indexed-object-style
+  public constructor(headers: { [header: string]: string } = {}) {
     super();
-    this.headers = {
-      'x-powered-by': 'Community Solid Server',
-    };
+    this.headers = { ...headers };
   }
 
   public async handle({ response }: { response: HttpResponse }): Promise<void> {

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

@@ -3,18 +3,24 @@ import { HeaderHandler } from '../../../../src/server/middleware/HeaderHandler';
 import { guardStream } from '../../../../src/util/GuardedStream';
 
 describe('a HeaderHandler', (): void => {
-  let handler: HeaderHandler;
+  it('adds no headers when none are configured.', async(): Promise<void> => {
+    const handler = new 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',
-    }));
+
+    expect(response.getHeaders()).toEqual({});
+  });
+
+  it('adds all configured headers.', async(): Promise<void> => {
+    const headers = { custom: 'Custom', other: 'Other' };
+    const handler = new HeaderHandler(headers);
+
+    const request = guardStream(createRequest());
+    const response = createResponse();
+    await handler.handleSafe({ request, response });
+
+    expect(response.getHeaders()).toEqual(expect.objectContaining(headers));
   });
 });