From 6574dba9028bd19d4ea3251517c1aba9e8a56563 Mon Sep 17 00:00:00 2001
From: "steven.guiheux" <steven.guiheux@ovhcloud.com>
Date: Tue, 19 May 2026 21:09:44 +0200
Subject: [PATCH] fix(ui): handle non-JSON error responses in form-fetch-action
 (#12635)

### Problem

When a user clicks the merge button on a pull request and their quota is exceeded, the UI displays ( cf screenshot ):

> Network error SyntaxError: Unexpected token 'Q', "Quota exceeded." is not valid JSON

### Fix

Read the response body as text first with `resp.text()`, then attempt `JSON.parse()`. If parsing succeeds, use the existing `errorMessage` logic. If it fails, display the raw text directly in the error toast.

This is the same approach already used by Dropzone for attachment uploads, where the `error` event handler passes the response body directly to `showErrorToast`. ( cf screenshot )

### Tests for JavaScript changes

The function is not exported, I cannot create a unit test. Do you want me to export all the logic in an exported function ?

### Release notes

- [X] This change will be noticed by a Forgejo user or admin (feature, bug fix, performance, etc.). I suggest to include a release note for this change.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/12635
Reviewed-by: Mathieu Fenniak <mfenniak@noreply.codeberg.org>
---
 web_src/js/features/common-global.js | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/web_src/js/features/common-global.js b/web_src/js/features/common-global.js
index fe644e099e..a5726e94e9 100644
--- a/web_src/js/features/common-global.js
+++ b/web_src/js/features/common-global.js
@@ -94,13 +94,19 @@ async function fetchActionDoRequest(actionElem, url, opt) {
       }
       return;
     } else if (resp.status >= 400 && resp.status < 500) {
-      const data = await resp.json();
-      // the code was quite messy, sometimes the backend uses "err", sometimes it uses "error", and even "user_error"
-      // but at the moment, as a new approach, we only use "errorMessage" here, backend can use JSONError() to respond.
-      if (data.errorMessage) {
-        showErrorToast(data.errorMessage, {useHtmlBody: data.renderFormat === 'html'});
-      } else {
-        showErrorToast(`server error: ${resp.status}`);
+      const text = await resp.text();
+      try {
+        const data = JSON.parse(text);
+        // the code was quite messy, sometimes the backend uses "err", sometimes it uses "error", and even "user_error"
+        // but at the moment, as a new approach, we only use "errorMessage" here, backend can use JSONError() to respond.
+        if (data.errorMessage) {
+          showErrorToast(data.errorMessage, {useHtmlBody: data.renderFormat === 'html'});
+        } else {
+          showErrorToast(`server error: ${resp.status}`);
+        }
+      } catch {
+        // if the response is not valid JSON (e.g. plain text "Quota exceeded."), show it directly
+        showErrorToast(text.trim() || `server error: ${resp.status}`);
       }
     } else {
       showErrorToast(`server error: ${resp.status}`);