feat: Normalize to GoogleAuth<AuthClient>

Author: d-goog

Diff for: src/auth/googleauth.ts

@@ -52,7 +52,7 @@ 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 +82,7 @@ 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 +114,12 @@ 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
@@ -163,7 +162,7 @@ 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.

Diff for: 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};