feat: Combine the results of multiple CredentialsExtractors

config/ldp/authentication/debug-auth-header.json

@@ -7,8 +7,8 @@
         "Supports authentication headers such as `Authentication: WebID http://test.com/card#me`"
       ],
       "@id": "urn:solid-server:default:CredentialsExtractor",
-      "@type": "WaterfallHandler",
-      "handlers": [
+      "@type": "UnionCredentialsExtractor",
+      "extractors": [
         { "@type": "UnsecureWebIdExtractor" },
         { "@type": "EmptyCredentialsExtractor" }
       ]

config/ldp/authentication/debug-test-agent.json

@@ -7,8 +7,14 @@
         "This extractor always sets the credentials to the fixed value."
       ],
       "@id": "urn:solid-server:default:CredentialsExtractor",
+      "@type": "UnionCredentialsExtractor",
+      "extractors": [
+        {
           "@type": "UnsecureConstantCredentialsExtractor",
           "agent": "http://test.com/card#me"
+        },
+        { "@type": "EmptyCredentialsExtractor" }
+      ]
     }
   ]
 }

config/ldp/authentication/dpop-bearer.json

@@ -4,6 +4,9 @@
     {
       "comment": "Supports DPoP and Bearer access tokens, or no credentials.",
       "@id": "urn:solid-server:default:CredentialsExtractor",
+      "@type": "UnionCredentialsExtractor",
+      "extractors": [
+        {
           "@type": "WaterfallHandler",
           "handlers": [
             {
@@ -12,7 +15,9 @@
                 "@type": "OriginalUrlExtractor"
               }
             },
-        { "@type": "BearerWebIdExtractor" },
+            { "@type": "BearerWebIdExtractor" }
+          ]
+        },
         { "@type": "EmptyCredentialsExtractor" }
       ]
     }

src/authentication/UnionCredentialsExtractor.ts

@@ -0,0 +1,27 @@
+import { UnionHandler } from '../util/handlers/UnionHandler';
+import type { CredentialGroup, Credential, CredentialSet } from './Credentials';
+
+import type { CredentialsExtractor } from './CredentialsExtractor';
+
+/**
+ * Combines the results of several CredentialsExtractors into one.
+ * If multiple of these extractors return a value for the same key,
+ * the last result will be used.
+ */
+export class UnionCredentialsExtractor extends UnionHandler<CredentialsExtractor> {
+  public constructor(extractors: CredentialsExtractor[]) {
+    super(extractors);
+  }
+
+  public async combine(results: CredentialSet[]): Promise<CredentialSet> {
+    // Combine all the results into a single object
+    return results.reduce((result, credential): CredentialSet => {
+      for (const [ key, value ] of Object.entries(credential) as [ CredentialGroup, Credential ][]) {
+        if (value) {
+          result[key] = value;
+        }
+      }
+      return result;
+    }, {});
+  }
+}

src/index.ts

@@ -4,6 +4,7 @@ export * from './authentication/Credentials';
 export * from './authentication/CredentialsExtractor';
 export * from './authentication/DPoPWebIdExtractor';
 export * from './authentication/EmptyCredentialsExtractor';
+export * from './authentication/UnionCredentialsExtractor';
 export * from './authentication/UnsecureConstantCredentialsExtractor';
 export * from './authentication/UnsecureWebIdExtractor';
 

src/util/handlers/HandlerUtil.ts

@@ -74,7 +74,7 @@ Promise<AsyncHandler<TIn, TOut>[]> {
     await handler.canHandle(input);
     return handler;
   }));
-  const matches = results.filter((result): boolean => result.status === 'fulfilled')
+  const matches = results.filter(({ status }): boolean => status === 'fulfilled')
     .map((result): AsyncHandler<TIn, TOut> =>
       (result as PromiseFulfilledResult<AsyncHandler<TIn, TOut>>).value);
 

test/unit/authentication/UnionCredentialsExtractor.test.ts

@@ -0,0 +1,46 @@
+import { CredentialGroup } from '../../../src/authentication/Credentials';
+import type { Credentials } from '../../../src/authentication/Credentials';
+import type { CredentialsExtractor } from '../../../src/authentication/CredentialsExtractor';
+import { UnionCredentialsExtractor } from '../../../src/authentication/UnionCredentialsExtractor';
+import type { HttpRequest } from '../../../src/server/HttpRequest';
+
+describe('A UnionCredentialsExtractor', (): void => {
+  const agent: Credentials = { [CredentialGroup.agent]: { webId: 'http://test.com/#me' }};
+  const everyone: Credentials = { [CredentialGroup.public]: {}};
+  const request: HttpRequest = {} as any;
+  let extractors: jest.Mocked<CredentialsExtractor>[];
+  let extractor: UnionCredentialsExtractor;
+
+  beforeEach(async(): Promise<void> => {
+    extractors = [
+      {
+        canHandle: jest.fn(),
+        handle: jest.fn().mockResolvedValue(agent),
+      } as any,
+      {
+        canHandle: jest.fn(),
+        handle: jest.fn().mockResolvedValue(everyone),
+      } as any,
+    ];
+
+    extractor = new UnionCredentialsExtractor(extractors);
+  });
+
+  it('combines the results of the extractors.', async(): Promise<void> => {
+    await expect(extractor.handle(request)).resolves.toEqual({
+      [CredentialGroup.agent]: agent.agent,
+      [CredentialGroup.public]: {},
+    });
+  });
+
+  it('ignores undefined values.', async(): Promise<void> => {
+    extractors[1].handle.mockResolvedValueOnce({
+      [CredentialGroup.public]: {},
+      [CredentialGroup.agent]: undefined,
+    });
+    await expect(extractor.handle(request)).resolves.toEqual({
+      [CredentialGroup.agent]: agent.agent,
+      [CredentialGroup.public]: {},
+    });
+  });
+});