Respect filename field on m.file events (#8951)

src/customisations/models/IMediaEventContent.ts

@@ -47,6 +47,7 @@ export interface IMediaEventInfo {
 
 export interface IMediaEventContent {
     body?: string;
+    filename?: string; // `m.file` optional field
     url?: string; // required on unencrypted media
     file?: IEncryptedFile; // required for *encrypted* media
     info?: IMediaEventInfo;

src/utils/MediaEventHelper.ts

@@ -47,7 +47,9 @@ export class MediaEventHelper implements IDestroyable {
     }
 
     public get fileName(): string {
-        return this.event.getContent<IMediaEventContent>().body || "download";
+        return this.event.getContent<IMediaEventContent>().filename
+            || this.event.getContent<IMediaEventContent>().body
+            || "download";
     }
 
     public destroy() {