feat!: Normalize GoogleAuth<T> from JSONClient to AuthClient

src/auth/googleauth.ts

@@ -26,17 +26,8 @@ import {CredentialBody, ImpersonatedJWTInput, JWTInput} from './credentials';
 import {IdTokenClient} from './idtokenclient';
 import {GCPEnv, getEnv} from './envDetect';
 import {JWT, JWTOptions} from './jwtclient';
-import {OAuth2ClientOptions} from './oauth2client';
-import {
-  UserRefreshClient,
-  UserRefreshClientOptions,
-  USER_REFRESH_ACCOUNT_TYPE,
-} from './refreshclient';
-import {
-  Impersonated,
-  ImpersonatedOptions,
-  IMPERSONATED_ACCOUNT_TYPE,
-} from './impersonated';
+import {UserRefreshClient, USER_REFRESH_ACCOUNT_TYPE} from './refreshclient';
+import {Impersonated, IMPERSONATED_ACCOUNT_TYPE} from './impersonated';
 import {
   ExternalAccountClient,
   ExternalAccountClientOptions,
@@ -52,7 +43,7 @@ import {
   ExternalAccountAuthorizedUserClientOptions,
 } from './externalAccountAuthorizedUserClient';
 import {originalOrCamelOptions} from '../util';
-import {AnyAuthClient} from '..';
+import {AnyAuthClient, AnyAuthClientConstructor} from '..';
 
 /**
  * Defines all types of explicit clients that are determined via ADC JSON
@@ -82,7 +73,7 @@ export interface ADCResponse {
   projectId: string | null;
 }
 
-export interface GoogleAuthOptions<T extends AuthClient = JSONClient> {
+export interface GoogleAuthOptions<T extends AuthClient = AnyAuthClient> {
   /**
    * An API key to use, optional. Cannot be used with {@link GoogleAuthOptions.credentials `credentials`}.
    */
@@ -114,13 +105,12 @@ export interface GoogleAuthOptions<T extends AuthClient = JSONClient> {
   credentials?: JWTInput | ExternalAccountClientOptions;
 
   /**
-   * Options object passed to the constructor of the client
+   * `AuthClientOptions` object passed to the constructor of the client
    */
-  clientOptions?:
-    | JWTOptions
-    | OAuth2ClientOptions
-    | UserRefreshClientOptions
-    | ImpersonatedOptions;
+  clientOptions?: Extract<
+    ConstructorParameters<AnyAuthClientConstructor>[0],
+    AuthClientOptions
+  >;
 
   /**
    * Required scopes for the desired API request
@@ -160,7 +150,7 @@ export const GoogleAuthExceptionMessages = {
     'https://cloud.google.com/compute/docs/metadata/predefined-metadata-keys',
 } as const;
 
-export class GoogleAuth<T extends AuthClient = JSONClient> {
+export class GoogleAuth<T extends AuthClient = AuthClient> {
   /**
    * Caches a value indicating whether the auth layer is running on Google
    * Compute Engine.

src/index.ts

@@ -91,12 +91,16 @@ export {PassThroughClient} from './auth/passthrough';
 type ALL_EXPORTS = (typeof import('./'))[keyof typeof import('./')];
 
 /**
- * A union type for all {@link AuthClient `AuthClient`}s.
+ * A union type for all {@link AuthClient `AuthClient`} constructors.
  */
-export type AnyAuthClient = InstanceType<
+export type AnyAuthClientConstructor =
   // Extract All `AuthClient`s from exports
-  Extract<ALL_EXPORTS, typeof AuthClient>
->;
+  Extract<ALL_EXPORTS, typeof AuthClient>;
+
+/**
+ * A union type for all {@link AuthClient `AuthClient`}s.
+ */
+export type AnyAuthClient = InstanceType<AnyAuthClientConstructor>;
 
 const auth = new GoogleAuth();
 export {auth, GoogleAuth};

test/test.googleauth.ts

@@ -41,6 +41,8 @@ import {
   ExternalAccountClientOptions,
   Impersonated,
   IdentityPoolClient,
+  PassThroughClient,
+  AnyAuthClient,
 } from '../src';
 import {CredentialBody} from '../src/auth/credentials';
 import * as envDetect from '../src/auth/envDetect';
@@ -62,7 +64,7 @@ import {stringify} from 'querystring';
 import {GoogleAuthExceptionMessages} from '../src/auth/googleauth';
 import {IMPERSONATED_ACCOUNT_TYPE} from '../src/auth/impersonated';
 import {USER_REFRESH_ACCOUNT_TYPE} from '../src/auth/refreshclient';
-import {Gaxios, GaxiosError} from 'gaxios';
+import {Gaxios, GaxiosError, GaxiosPromise, GaxiosResponse} from 'gaxios';
 
 nock.disableNetConnect();
 
@@ -283,6 +285,52 @@ describe('googleauth', () => {
       return sandbox.stub(process, 'env').value(envVars);
     }
 
+    describe('types', () => {
+      it('should be type-compatible with itself by default', () => {
+        class CustomAuthClient extends AuthClient {
+          request<T>(): GaxiosPromise<T> {
+            throw new Error('Method not implemented.');
+          }
+          getRequestHeaders(): Promise<Headers> {
+            throw new Error('Method not implemented.');
+          }
+          getAccessToken(): Promise<{
+            token?: string | null;
+            res?: GaxiosResponse | null;
+          }> {
+            throw new Error('Method not implemented.');
+          }
+        }
+
+        // default > default
+        const defaultToDefault: GoogleAuth = new GoogleAuth();
+
+        // Explicit > default
+        const explicitToDefault: GoogleAuth =
+          new GoogleAuth<PassThroughClient>();
+
+        // custom > default
+        const customToDefault: GoogleAuth = new GoogleAuth<CustomAuthClient>();
+
+        // AnyAuthClient > default
+        const anyToDefault: GoogleAuth = new GoogleAuth<AnyAuthClient>();
+
+        // default > AnyAuthClient
+        const defaultToAny: GoogleAuth<AnyAuthClient> = new GoogleAuth();
+
+        // AuthClient > AnyAuthClient
+        const baseClientToAny: GoogleAuth<AnyAuthClient> =
+          new GoogleAuth<AuthClient>();
+
+        assert(defaultToDefault);
+        assert(explicitToDefault);
+        assert(customToDefault);
+        assert(anyToDefault);
+        assert(defaultToAny);
+        assert(baseClientToAny);
+      });
+    });
+
     it('should accept and use an `AuthClient`', async () => {
       const customRequestHeaders = new Headers({
         'my-unique': 'header',