feat(Client): add conditional ready typings (#6073)

src/client/Client.js

@@ -18,7 +18,7 @@ const VoiceRegion = require('../structures/VoiceRegion');
 const Webhook = require('../structures/Webhook');
 const Widget = require('../structures/Widget');
 const Collection = require('../util/Collection');
-const { Events, InviteScopes } = require('../util/Constants');
+const { Events, InviteScopes, Status } = require('../util/Constants');
 const DataResolver = require('../util/DataResolver');
 const Intents = require('../util/Intents');
 const Options = require('../util/Options');
@@ -227,6 +227,15 @@ class Client extends BaseClient {
     }
   }
 
+  /**
+   * Returns whether the client has logged in, indicative of being able to access
+   * properties such as `user` and `application`.
+   * @returns {boolean}
+   */
+  isReady() {
+    return this.ws.status === Status.READY;
+  }
+
   /**
    * Logs out, terminates the connection to Discord, and destroys the client.
    * @returns {void}

src/client/websocket/WebSocketManager.js

@@ -373,8 +373,9 @@ class WebSocketManager extends EventEmitter {
     /**
      * Emitted when the client becomes ready to start working.
      * @event Client#ready
+     * @param {Client} client The client
      */
-    this.client.emit(Events.CLIENT_READY);
+    this.client.emit(Events.CLIENT_READY, this.client);
 
     this.handlePacket();
   }

typings/index.d.ts

@@ -278,23 +278,25 @@ export class Channel extends Base {
   public toString(): ChannelMention;
 }
 
-export class Client extends BaseClient {
+type If<T extends boolean, A, B = null> = T extends true ? A : T extends false ? B : A | B;
+
+export class Client<Ready extends boolean = boolean> extends BaseClient {
   public constructor(options: ClientOptions);
   private actions: unknown;
   private _eval(script: string): unknown;
   private _validateOptions(options: ClientOptions): void;
 
-  public application: ClientApplication | null;
+  public application: If<Ready, ClientApplication>;
   public channels: ChannelManager;
   public readonly emojis: BaseGuildEmojiManager;
   public guilds: GuildManager;
   public options: ClientOptions;
-  public readyAt: Date | null;
-  public readonly readyTimestamp: number | null;
+  public readyAt: If<Ready, Date>;
+  public readonly readyTimestamp: If<Ready, number>;
   public shard: ShardClientUtil | null;
-  public token: string | null;
-  public readonly uptime: number | null;
-  public user: ClientUser | null;
+  public token: If<Ready, string, string | null>;
+  public uptime: If<Ready, number>;
+  public user: If<Ready, ClientUser>;
   public users: UserManager;
   public voice: ClientVoiceManager;
   public ws: WebSocketManager;
@@ -307,6 +309,7 @@ export class Client extends BaseClient {
   public fetchWidget(guild: GuildResolvable): Promise<Widget>;
   public generateInvite(options?: InviteGenerationOptions): string;
   public login(token?: string): Promise<string>;
+  public isReady(): this is Client<true>;
   public sweepMessages(lifetime?: number): number;
   public toJSON(): unknown;
 
@@ -2818,7 +2821,7 @@ export interface ClientEvents {
   presenceUpdate: [oldPresence: Presence | null, newPresence: Presence];
   rateLimit: [rateLimitData: RateLimitData];
   invalidRequestWarning: [invalidRequestWarningData: InvalidRequestWarningData];
-  ready: [];
+  ready: [client: Client<true>];
   invalidated: [];
   roleCreate: [role: Role];
   roleDelete: [role: Role];

typings/index.ts

@@ -5,6 +5,8 @@ import {
   ApplicationCommandResolvable,
   CategoryChannel,
   Client,
+  ClientApplication,
+  ClientUser,
   Collection,
   Constants,
   DMChannel,
@@ -447,6 +449,27 @@ client.on('interaction', async interaction => {
 
 client.login('absolutely-valid-token');
 
+// Test client conditional types
+client.on('ready', client => {
+  assertType<Client<true>>(client);
+});
+
+declare const loggedInClient: Client<true>;
+assertType<ClientApplication>(loggedInClient.application);
+assertType<Date>(loggedInClient.readyAt);
+assertType<number>(loggedInClient.readyTimestamp);
+assertType<string>(loggedInClient.token);
+assertType<number>(loggedInClient.uptime);
+assertType<ClientUser>(loggedInClient.user);
+
+declare const loggedOutClient: Client<false>;
+assertType<null>(loggedOutClient.application);
+assertType<null>(loggedOutClient.readyAt);
+assertType<null>(loggedOutClient.readyTimestamp);
+assertType<string | null>(loggedOutClient.token);
+assertType<null>(loggedOutClient.uptime);
+assertType<null>(loggedOutClient.user);
+
 // Test type transformation:
 declare const assertType: <T>(value: T) => asserts value is T;
 declare const serialize: <T>(value: T) => Serialized<T>;