feat(MessageAttachment): allow files to be marked as spoilers (#6509)

Co-authored-by: Antonio Román <kyradiscord@gmail.com>

src/structures/MessageAttachment.js

@@ -43,6 +43,24 @@ class MessageAttachment {
     return this;
   }
 
+  /**
+   * Sets whether this attachment is a spoiler
+   * @param {boolean} [spoiler=true] Whether the attachment should be marked as a spoiler
+   * @returns {MessageAttachment} This attachment
+   */
+  setSpoiler(spoiler = true) {
+    if (spoiler === this.spoiler) return this;
+
+    if (!spoiler) {
+      while (this.spoiler) {
+        this.name.slice('SPOILER_'.length);
+      }
+      return this;
+    }
+    this.name = `SPOILER_${this.name}`;
+    return this;
+  }
+
   _patch(data) {
     /**
      * The attachment's id
@@ -93,7 +111,7 @@ class MessageAttachment {
    * @readonly
    */
   get spoiler() {
-    return Util.basename(this.url).startsWith('SPOILER_');
+    return Util.basename(this.url ?? this.name).startsWith('SPOILER_');
   }
 
   toJSON() {

typings/index.d.ts

@@ -1210,6 +1210,7 @@ export class MessageAttachment {
   public width: number | null;
   public setFile(attachment: BufferResolvable | Stream, name?: string): this;
   public setName(name: string): this;
+  public setSpoiler(spoiler?: boolean): this;
   public toJSON(): unknown;
 }