feat(REST): append additional information to the required User Agent (#6112)

Co-authored-by: Vlad Frangu <kingdgrizzle@gmail.com>

src/client/Client.js

@@ -520,6 +520,9 @@ class Client extends BaseClient {
     if (typeof options.failIfNotExists !== 'boolean') {
       throw new TypeError('CLIENT_INVALID_OPTION', 'failIfNotExists', 'a boolean');
     }
+    if (!Array.isArray(options.userAgentSuffix)) {
+      throw new TypeError('CLIENT_INVALID_OPTION', 'userAgentSuffix', 'an array of strings');
+    }
     if (
       typeof options.rejectOnRateLimit !== 'undefined' &&
       !(typeof options.rejectOnRateLimit === 'function' || Array.isArray(options.rejectOnRateLimit))

src/rest/APIRequest.js

@@ -17,6 +17,9 @@ class APIRequest {
     this.options = options;
     this.retries = 0;
 
+    const { userAgentSuffix } = this.client.options;
+    this.fullUserAgent = `${UserAgent}${userAgentSuffix.length ? `, ${userAgentSuffix.join(', ')}` : ''}`;
+
     let queryString = '';
     if (options.query) {
       const query = Object.entries(options.query)
@@ -33,11 +36,14 @@ class APIRequest {
         ? this.client.options.http.api
         : `${this.client.options.http.api}/v${this.client.options.http.version}`;
     const url = API + this.path;
-    let headers = { ...this.client.options.http.headers };
+
+    let headers = {
+      ...this.client.options.http.headers,
+      'User-Agent': this.fullUserAgent,
+    };
 
     if (this.options.auth !== false) headers.Authorization = this.rest.getAuth();
     if (this.options.reason) headers['X-Audit-Log-Reason'] = encodeURIComponent(this.options.reason);
-    headers['User-Agent'] = UserAgent;
     if (this.options.headers) headers = Object.assign(headers, this.options.headers);
 
     let body;

src/util/Options.js

@@ -62,6 +62,8 @@
  * {@link RateLimitError} will be thrown. Otherwise the request will be queued for later
  * @property {number} [retryLimit=1] How many times to retry on 5XX errors (Infinity for indefinite amount of retries)
  * @property {boolean} [failIfNotExists=true] Default value for {@link ReplyMessageOptions#failIfNotExists}
+ * @property {string[]} [userAgentSuffix] An array of additional bot info to be appended to the end of the required
+ * [User Agent](https://discord.com/developers/docs/reference#user-agent) header
  * @property {PresenceData} [presence={}] Presence data to use upon login
  * @property {IntentsResolvable} intents Intents to enable for this connection
  * @property {WebsocketOptions} [ws] Options for the WebSocket
@@ -109,6 +111,7 @@ class Options extends null {
       restTimeOffset: 500,
       restSweepInterval: 60,
       failIfNotExists: true,
+      userAgentSuffix: [],
       presence: {},
       ws: {
         large_threshold: 50,