feat: Handle OPTIONS requests in OperationHandler

config/http/middleware/handlers/cors.json

@@ -15,6 +15,7 @@
         "DELETE"
       ],
       "options_credentials": true,
+      "options_preflightContinue": true,
       "options_exposedHeaders": [
         "Accept-Patch",
         "ETag",

config/ldp/handler/components/operation-handler.json

@@ -5,9 +5,13 @@
       "@id": "urn:solid-server:default:OperationHandler",
       "@type": "WaterfallHandler",
       "handlers": [
+        {
+          "@type": "OptionsOperationHandler",
+          "resourceSet": { "@id": "urn:solid-server:default:CachedResourceSet" }
+        },
         {
           "@type": "GetOperationHandler",
-          "store": { "@id": "urn:solid-server:default:ResourceStore" },
+          "store": { "@id": "urn:solid-server:default:ResourceStore" }
         },
         {
           "@type": "PostOperationHandler",
@@ -23,7 +27,7 @@
         },
         {
           "@type": "HeadOperationHandler",
-          "store": { "@id": "urn:solid-server:default:ResourceStore" },
+          "store": { "@id": "urn:solid-server:default:ResourceStore" }
         },
         {
           "@type": "PatchOperationHandler",

src/authorization/permissions/MethodModesExtractor.ts

@@ -5,7 +5,7 @@ import { isContainerIdentifier } from '../../util/PathUtil';
 import { ModesExtractor } from './ModesExtractor';
 import { AccessMode } from './Permissions';
 
-const READ_METHODS = new Set([ 'GET', 'HEAD' ]);
+const READ_METHODS = new Set([ 'OPTIONS', 'GET', 'HEAD' ]);
 const SUPPORTED_METHODS = new Set([ ...READ_METHODS, 'PUT', 'POST', 'DELETE' ]);
 
 /**

src/http/ldp/OptionsOperationHandler.ts

@@ -0,0 +1,36 @@
+import type { ResourceSet } from '../../storage/ResourceSet';
+import { NotFoundHttpError } from '../../util/errors/NotFoundHttpError';
+import { NotImplementedHttpError } from '../../util/errors/NotImplementedHttpError';
+import { NoContentResponseDescription } from '../output/response/NoContentResponseDescription';
+import type { ResponseDescription } from '../output/response/ResponseDescription';
+import type { OperationHandlerInput } from './OperationHandler';
+import { OperationHandler } from './OperationHandler';
+
+/**
+ * Handles OPTIONS {@link Operation}s by always returning a 204.
+ */
+export class OptionsOperationHandler extends OperationHandler {
+  private readonly resourceSet: ResourceSet;
+
+  /**
+   * Uses a {@link ResourceSet} to determine the existence of the target resource which impacts the response code.
+   * @param resourceSet - {@link ResourceSet} that knows if the target resource exists or not.
+   */
+  public constructor(resourceSet: ResourceSet) {
+    super();
+    this.resourceSet = resourceSet;
+  }
+
+  public async canHandle({ operation }: OperationHandlerInput): Promise<void> {
+    if (operation.method !== 'OPTIONS') {
+      throw new NotImplementedHttpError('This handler only supports OPTIONS operations');
+    }
+  }
+
+  public async handle({ operation }: OperationHandlerInput): Promise<ResponseDescription> {
+    if (!await this.resourceSet.hasResource(operation.target)) {
+      throw new NotFoundHttpError();
+    }
+    return new NoContentResponseDescription();
+  }
+}

src/http/output/response/NoContentResponseDescription.ts

@@ -0,0 +1,10 @@
+import { ResponseDescription } from './ResponseDescription';
+
+/**
+ * Corresponds to a 204 response.
+ */
+export class NoContentResponseDescription extends ResponseDescription {
+  public constructor() {
+    super(204);
+  }
+}

src/index.ts

@@ -82,6 +82,7 @@ export * from './http/ldp/DeleteOperationHandler';
 export * from './http/ldp/GetOperationHandler';
 export * from './http/ldp/HeadOperationHandler';
 export * from './http/ldp/OperationHandler';
+export * from './http/ldp/OptionsOperationHandler';
 export * from './http/ldp/PatchOperationHandler';
 export * from './http/ldp/PostOperationHandler';
 export * from './http/ldp/PutOperationHandler';
@@ -103,6 +104,7 @@ export * from './http/output/metadata/WwwAuthMetadataWriter';
 
 // HTTP/Output/Response
 export * from './http/output/response/CreatedResponseDescription';
+export * from './http/output/response/NoContentResponseDescription';
 export * from './http/output/response/OkResponseDescription';
 export * from './http/output/response/ResetResponseDescription';
 export * from './http/output/response/ResponseDescription';

src/server/middleware/CorsHandler.ts

@@ -21,12 +21,13 @@ interface SimpleCorsOptions {
 
 /**
  * Handler that sets CORS options on the response.
- * In case of an OPTIONS request this handler will close the connection after adding its headers.
+ * In case of an OPTIONS request this handler will close the connection after adding its headers
+ * if `preflightContinue` is set to `false`.
  *
- * Solid, §7.1: "A data pod MUST implement the CORS protocol [FETCH] such that, to the extent possible,
+ * Solid, §8.1: "A server MUST implement the CORS protocol [FETCH] such that, to the extent possible,
- * the browser allows Solid apps to send any request and combination of request headers to the data pod,
+ * the browser allows Solid apps to send any request and combination of request headers to the server,
- * and the Solid app can read any response and response headers received from the data pod."
+ * and the Solid app can read any response and response headers received from the server."
- * Full details: https://solid.github.io/specification/protocol#cors-server
+ * Full details: https://solidproject.org/TR/2021/protocol-20211217#cors-server
  */
 export class CorsHandler extends HttpHandler {
   private readonly corsHandler: (

test/integration/Middleware.test.ts

@@ -70,7 +70,7 @@ describe('An http server with middleware', (): void => {
       .set('Access-Control-Request-Headers', 'content-type')
       .set('Access-Control-Request-Method', 'POST')
       .set('Host', 'test.com')
-      .expect(204);
+      .expect(200);
     expect(res.header).toEqual(expect.objectContaining({
       'access-control-allow-origin': '*',
       'access-control-allow-headers': 'content-type',

test/integration/PermissionTable.test.ts

@@ -44,10 +44,9 @@ const allModes = [ AM.read, AM.append, AM.create, AM.write, AM.delete ];
 // For PUT/PATCH/DELETE we return 205 instead of 200/204
 /* eslint-disable no-multi-spaces */
 const table: [string, string, AM[], AM[] | undefined, string, string, number, number][] = [
-  // We currently handle OPTIONS before authorization
+  [ 'OPTIONS', 'C/R', [],                     undefined,              '',     '',  401, 401 ],
-  // [ 'OPTIONS', 'C/R', [],                     undefined,              '',     '',  401, 401 ],
+  [ 'OPTIONS', 'C/R', [],                     [ AM.read ],            '',     '',  204, 404 ],
-  // [ 'OPTIONS', 'C/R', [],                     [ AM.read ],            '',     '',  200, 404 ],
+  [ 'OPTIONS', 'C/R', [ AM.read ],            undefined,              '',     '',  204, 404 ],
-  // [ 'OPTIONS', 'C/R', [ AM.read ],            undefined,              '',     '',  200, 404 ],
 
   [ 'HEAD',    'C/R', [],                     undefined,              '',     '',  401, 401 ],
   [ 'HEAD',    'C/R', [],                     [ AM.read ],            '',     '',  200, 404 ],

test/unit/http/ldp/OptionsOperationHandler.test.ts

@@ -0,0 +1,44 @@
+import { OptionsOperationHandler } from '../../../../src/http/ldp/OptionsOperationHandler';
+import type { Operation } from '../../../../src/http/Operation';
+import { BasicRepresentation } from '../../../../src/http/representation/BasicRepresentation';
+import { BasicConditions } from '../../../../src/storage/BasicConditions';
+import type { ResourceSet } from '../../../../src/storage/ResourceSet';
+import { NotFoundHttpError } from '../../../../src/util/errors/NotFoundHttpError';
+import { NotImplementedHttpError } from '../../../../src/util/errors/NotImplementedHttpError';
+
+describe('An OptionsOperationHandler', (): void => {
+  let operation: Operation;
+  const conditions = new BasicConditions({});
+  const preferences = {};
+  const body = new BasicRepresentation();
+  let resourceSet: jest.Mocked<ResourceSet>;
+  let handler: OptionsOperationHandler;
+
+  beforeEach(async(): Promise<void> => {
+    operation = { method: 'OPTIONS', target: { path: 'http://test.com/foo' }, preferences, conditions, body };
+    resourceSet = {
+      hasResource: jest.fn().mockResolvedValue(true),
+    };
+    handler = new OptionsOperationHandler(resourceSet);
+  });
+
+  it('only supports Options operations.', async(): Promise<void> => {
+    await expect(handler.canHandle({ operation })).resolves.toBeUndefined();
+    operation.method = 'GET';
+    await expect(handler.canHandle({ operation })).rejects.toThrow(NotImplementedHttpError);
+    operation.method = 'HEAD';
+    await expect(handler.canHandle({ operation })).rejects.toThrow(NotImplementedHttpError);
+  });
+
+  it('returns a 204 response.', async(): Promise<void> => {
+    const result = await handler.handle({ operation });
+    expect(result.statusCode).toBe(204);
+    expect(result.metadata).toBeUndefined();
+    expect(result.data).toBeUndefined();
+  });
+
+  it('returns a 404 if the target resource does not exist.', async(): Promise<void> => {
+    resourceSet.hasResource.mockResolvedValueOnce(false);
+    await expect(handler.handle({ operation })).rejects.toThrow(NotFoundHttpError);
+  });
+});