From 33d3df24f925c01eb0254e393140501f18f357cf Mon Sep 17 00:00:00 2001
From: Hugh Nimmo-Smith <hughns@users.noreply.github.com>
Date: Fri, 12 Sep 2025 11:28:40 +0100
Subject: [PATCH] Fix handling of 413 server response when uploading media
 (#30737)

---
 src/ContentMessages.ts                  | 18 ++++++++++++-----
 test/unit-tests/ContentMessages-test.ts | 26 +++++++++++++++++++++++++
 2 files changed, 39 insertions(+), 5 deletions(-)

diff --git a/src/ContentMessages.ts b/src/ContentMessages.ts
index 54aaea3ae1..e608b3470a 100644
--- a/src/ContentMessages.ts
+++ b/src/ContentMessages.ts
@@ -63,7 +63,12 @@ import { blobIsAnimated } from "./utils/Image.ts";
 const PHYS_HIDPI = [0x00, 0x00, 0x16, 0x25, 0x00, 0x00, 0x16, 0x25, 0x01];
 
 export class UploadCanceledError extends Error {}
-export class UploadFailedError extends Error {}
+export class UploadFailedError extends Error {
+    public constructor(cause: any) {
+        super();
+        this.cause = cause;
+    }
+}
 
 interface IMediaConfig {
     "m.upload.size"?: number;
@@ -367,7 +372,7 @@ export async function uploadFile(
         } catch (e) {
             if (abortController.signal.aborted) throw new UploadCanceledError();
             console.error("Failed to upload file", e);
-            throw new UploadFailedError();
+            throw new UploadFailedError(e);
         }
         if (abortController.signal.aborted) throw new UploadCanceledError();
 
@@ -386,7 +391,7 @@ export async function uploadFile(
         } catch (e) {
             if (abortController.signal.aborted) throw new UploadCanceledError();
             console.error("Failed to upload file", e);
-            throw new UploadFailedError();
+            throw new UploadFailedError(e);
         }
         if (abortController.signal.aborted) throw new UploadCanceledError();
         // If the attachment isn't encrypted then include the URL directly.
@@ -638,15 +643,18 @@ export default class ContentMessages {
             dis.dispatch<UploadFinishedPayload>({ action: Action.UploadFinished, upload });
             dis.dispatch({ action: "message_sent" });
         } catch (error) {
+            // Unwrap UploadFailedError to get the underlying error
+            const unwrappedError = error instanceof UploadFailedError && error.cause ? error.cause : error;
+
             // 413: File was too big or upset the server in some way:
             // clear the media size limit so we fetch it again next time we try to upload
-            if (error instanceof HTTPError && error.httpStatus === 413) {
+            if (unwrappedError instanceof HTTPError && unwrappedError.httpStatus === 413) {
                 this.mediaConfig = null;
             }
 
             if (!upload.cancelled) {
                 let desc = _t("upload_failed_generic", { fileName: upload.fileName });
-                if (error instanceof HTTPError && error.httpStatus === 413) {
+                if (unwrappedError instanceof HTTPError && unwrappedError.httpStatus === 413) {
                     desc = _t("upload_failed_size", {
                         fileName: upload.fileName,
                     });
diff --git a/test/unit-tests/ContentMessages-test.ts b/test/unit-tests/ContentMessages-test.ts
index 80b400568e..51bb73fbfd 100644
--- a/test/unit-tests/ContentMessages-test.ts
+++ b/test/unit-tests/ContentMessages-test.ts
@@ -10,6 +10,7 @@ import { mocked } from "jest-mock";
 import {
     type ISendEventResponse,
     type MatrixClient,
+    MatrixError,
     RelationType,
     type UploadResponse,
 } from "matrix-js-sdk/src/matrix";
@@ -20,6 +21,9 @@ import ContentMessages, { UploadCanceledError, uploadFile } from "../../src/Cont
 import { doMaybeLocalRoomAction } from "../../src/utils/local-room";
 import { createTestClient, flushPromises, mkEvent } from "../test-utils";
 import { BlurhashEncoder } from "../../src/BlurhashEncoder";
+import Modal from "../../src/Modal";
+import ErrorDialog from "../../src/components/views/dialogs/ErrorDialog";
+import { _t } from "../../src/languageHandler";
 
 jest.mock("matrix-encrypt-attachment", () => ({ encryptAttachment: jest.fn().mockResolvedValue({}) }));
 
@@ -291,6 +295,28 @@ describe("ContentMessages", () => {
                 }),
             );
         });
+
+        it("handles 413 error", async () => {
+            mocked(client.uploadContent).mockRejectedValue(
+                new MatrixError(
+                    {
+                        errcode: "M_TOO_LARGE",
+                        error: "File size limit exceeded",
+                    },
+                    413,
+                ),
+            );
+            const file = new File([], "fileName", { type: "image/jpeg" });
+            const dialogSpy = jest.spyOn(Modal, "createDialog");
+            await contentMessages.sendContentToRoom(file, roomId, undefined, client, undefined);
+            expect(dialogSpy).toHaveBeenCalledWith(
+                ErrorDialog,
+                expect.objectContaining({
+                    description: _t("upload_failed_size", { fileName: "fileName" }),
+                }),
+            );
+            dialogSpy.mockRestore();
+        });
     });
 
     describe("getCurrentUploads", () => {