backend-common: update createLegacyAuthAdapters to work with a single service

Co-authored-by: Fredrik Adelöw <freben@gmail.com>
Co-authored-by: Carl-Erik Bergström <cbergstrom@spotify.com>
Co-authored-by: blam <ben@blam.sh>
Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

packages/backend-common/api-report.md

@@ -235,16 +235,35 @@ export function createDatabaseClient(
 ): knexFactory.Knex<any, any[]>;
 
 // @public (undocumented)
-export function createLegacyAuthAdapters(options: {
-  auth?: AuthService;
-  httpAuth?: HttpAuthService;
-  identity?: IdentityService;
-  tokenManager?: TokenManager;
-  discovery: PluginEndpointDiscovery;
-}): {
-  auth: AuthService;
-  httpAuth: HttpAuthService;
-};
+export function createLegacyAuthAdapters<
+  TOptions extends {
+    auth?: AuthService;
+    httpAuth?: HttpAuthService;
+    identity?: IdentityService;
+    tokenManager?: TokenManager;
+    discovery: PluginEndpointDiscovery;
+  },
+  TAdapters = TOptions extends {
+    auth?: AuthService;
+  }
+    ? TOptions extends {
+        httpAuth?: HttpAuthService;
+      }
+      ? {
+          auth: AuthService;
+          httpAuth: HttpAuthService;
+        }
+      : {
+          auth: AuthService;
+        }
+    : TOptions extends {
+        httpAuth?: HttpAuthService;
+      }
+    ? {
+        httpAuth: HttpAuthService;
+      }
+    : 'error: at least one of auth and/or httpAuth must be provided',
+>(options: TOptions): TAdapters;
 
 // @public
 export function createRootLogger(

packages/backend-common/src/auth/createLegacyAuthAdapters.test.ts

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2024 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import { mockServices } from '@backstage/backend-test-utils';
+import { createLegacyAuthAdapters } from './createLegacyAuthAdapters';
+
+describe('createLegacyAuthAdapters', () => {
+  it('should pass through auth if only auth is provided', () => {
+    const auth = {};
+    const ret = createLegacyAuthAdapters({
+      auth: auth as any,
+      tokenManager: mockServices.tokenManager(),
+      discovery: {} as any,
+      identity: mockServices.identity(),
+    });
+
+    expect(ret.auth).toBe(auth);
+  });
+
+  it('should pass through httpAuth if only httpAuth is provided', () => {
+    const httpAuth = {};
+    const ret = createLegacyAuthAdapters({
+      httpAuth: httpAuth as any,
+      tokenManager: mockServices.tokenManager(),
+      discovery: {} as any,
+      identity: mockServices.identity(),
+    });
+
+    expect(ret.httpAuth).toBe(httpAuth);
+  });
+
+  it('should pass through both auth and httpAuth if both are provided', () => {
+    const auth = {};
+    const httpAuth = {};
+    const ret = createLegacyAuthAdapters({
+      auth: auth as any,
+      httpAuth: httpAuth as any,
+      tokenManager: mockServices.tokenManager(),
+      discovery: {} as any,
+      identity: mockServices.identity(),
+    });
+
+    expect(ret.auth).toBe(auth);
+    expect(ret.httpAuth).toBe(httpAuth);
+  });
+
+  it('should adapt both auth and httpAuth if neither are provided', () => {
+    const ret = createLegacyAuthAdapters({
+      auth: undefined,
+      httpAuth: undefined,
+      tokenManager: mockServices.tokenManager(),
+      discovery: {} as any,
+      identity: mockServices.identity(),
+    });
+
+    expect(ret).toEqual({
+      auth: expect.any(Object),
+      httpAuth: expect.any(Object),
+    });
+  });
+});

packages/backend-common/src/auth/createLegacyAuthAdapters.ts

@@ -210,29 +210,47 @@ class HttpAuthCompat implements HttpAuthService {
   async issueUserCookie(_res: Response): Promise<void> {}
 }
 
-/** @public */
-export function createLegacyAuthAdapters(options: {
-  auth?: AuthService;
-  httpAuth?: HttpAuthService;
-  identity?: IdentityService;
-  tokenManager?: TokenManager;
-  discovery: PluginEndpointDiscovery;
-}): {
-  auth: AuthService;
-  httpAuth: HttpAuthService;
-} {
+/**
+ * An adapter that ensures presence of the auth and/or httpAuth services.
+ * @public
+ */
+export function createLegacyAuthAdapters<
+  TOptions extends {
+    auth?: AuthService;
+    httpAuth?: HttpAuthService;
+    identity?: IdentityService;
+    tokenManager?: TokenManager;
+    discovery: PluginEndpointDiscovery;
+  },
+  TAdapters = TOptions extends {
+    auth?: AuthService;
+  }
+    ? TOptions extends { httpAuth?: HttpAuthService }
+      ? { auth: AuthService; httpAuth: HttpAuthService }
+      : { auth: AuthService }
+    : TOptions extends { httpAuth?: HttpAuthService }
+    ? { httpAuth: HttpAuthService }
+    : 'error: at least one of auth and/or httpAuth must be provided',
+>(options: TOptions): TAdapters {
   const { auth, httpAuth, discovery } = options;
 
-  if (auth || httpAuth) {
-    // TODO: Is this sensible? Could be that a lot of plugins only want one of them and in
-    // that case overloads might be better, so that it's possible to only provide one of them.
-    if (!(auth && httpAuth)) {
-      throw new Error('Both auth and httpAuth must be provided');
-    }
+  if (auth && httpAuth) {
     return {
       auth,
       httpAuth,
-    };
+    } as TAdapters;
+  }
+
+  if (auth) {
+    return {
+      auth,
+    } as TAdapters;
+  }
+
+  if (httpAuth) {
+    return {
+      httpAuth,
+    } as TAdapters;
   }
 
   const identity =
@@ -240,10 +258,11 @@ export function createLegacyAuthAdapters(options: {
   const tokenManager = options.tokenManager ?? ServerTokenManager.noop();
 
   const authImpl = new AuthCompat(identity, tokenManager);
+
   const httpAuthImpl = new HttpAuthCompat(authImpl);
 
   return {
     auth: authImpl,
     httpAuth: httpAuthImpl,
-  };
+  } as TAdapters;
 }