Qt6/Python 3.12 crash: QDialog.Accepted and QHttpMultiPart.FormDataType enums not found

[Linus-007]

What is the bug or the crash? What were your expectations and what actually happened?

Environment

OS: Windows 11
QGIS: 3.40.14 LTR (Qt 6)
Python: 3.12.12
QFieldSync plugin: [PUT VERSION HERE]

Description

On QGIS 3.40 (Qt6 / Python 3.12), QFieldSync crashes during

1. QField Cloud login, and
2. QField Cloud upload

Errors indicate use of Qt5-style enums that no longer exist in Qt6.

Error 1 (login crash)

AttributeError: type object 'QDialog' has no attribute 'Accepted'

Error 2 (upload crash)

AttributeError: type object 'QHttpMultiPart' has no attribute 'FormDataType'

Failing code paths

cloud_login_dialog.py

self.done(QDialog.Accepted)

cloud_api.py

QHttpMultiPart(QHttpMultiPart.FormDataType)

Qt6-correct equivalents

self.done(QDialog.DialogCode.Accepted)
QHttpMultiPart(QHttpMultiPart.ContentType.FormDataType)

Workaround

Manually patching the above lines resolves both crashes and allows
QField Cloud project creation and upload to complete successfully.

Impact

QField Cloud is unusable on QGIS 3.40 LTR + Python 3.12 without manual patching.

Reinstalling does not resolve it

Stale wheel caching appears to mask fixes

Steps to reproduce the issue

An error has occurred while executing Python code: AttributeError: type object 'QHttpMultiPart' has no attribute 'FormDataType' Traceback (most recent call last): File "C:\Users/linus/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\qfieldsync\core\cloud_transferrer.py", line 313, in _on_localized_datasets_upload_finished self._upload() File "C:\Users/linus/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\qfieldsync\core\cloud_transferrer.py", line 222, in _upload self.throttled_uploader.transfer() File "C:\Users/linus/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\qfieldsync\core\cloud_transferrer.py", line 737, in transfer transfer.transfer() File "C:\Users/linus/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\qfieldsync\core\cloud_transferrer.py", line 536, in transfer reply = self.network_manager.cloud_upload_files( ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "C:\Users/linus/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\qfieldsync\core\cloud_api.py", line 850, in cloud_upload_files multi_part = QHttpMultiPart(QHttpMultiPart.FormDataType) ^^^^^^^^^^^^^^^^^^^^^^^^^^^ AttributeError: type object 'QHttpMultiPart' has no attribute 'FormDataType' Python version: 3.12.12 (main, Oct 14 2025, 23:38:06) [MSC v.1944 64 bit (AMD64)] QGIS version: 3.40.14-Bratislava Bratislava, ebe1e1f3 Python Path: C:/PROGRA1/QGISQT1.14/apps/qgis-ltr-qt6/./python C:/Users/linus/AppData/Roaming/QGIS/QGIS3\profiles\default/python C:/Users/linus/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins C:/PROGRA1/QGISQT1.14/apps/qgis-ltr-qt6/./python/plugins C:\PROGRA1\QGISQT1.14\apps\grass\grass84\etc\python C:\Users\linus\Documents C:\Program Files\QGISQT6 3.40.14\bin\python312.zip C:\PROGRA1\QGISQT1.14\apps\Python312\DLLs C:\PROGRA1\QGISQT1.14\apps\Python312\Lib C:\Program Files\QGISQT6 3.40.14\bin C:\PROGRA1\QGISQT1.14\apps\Python312 C:\PROGRA1\QGISQT1.14\apps\Python312\Lib\site-packages C:\PROGRA1\QGISQT1.14\apps\Python312\Lib\site-packages\win32 C:\PROGRA1\QGISQT1.14\apps\Python312\Lib\site-packages\win32\lib C:\PROGRA1\QGISQT1.14\apps\Python312\Lib\site-packages\Pythonwin C:/Users/linus/AppData/Roaming/QGIS/QGIS3\profiles\default/python C:\Users\linus\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\qfieldsync\libqfieldsync_ed003e83912f1e28435d0789afc67acf17c44be8.whl

QGIS version

3.40.14-Bratislava

QFieldSync Version

qfieldsync-v4.18.0

Operating system name

Windows

Operating system version

11

Reinstall QFieldSync

• I have a fresh install of the latest QFieldSync version on a new QGIS profile, but the problem persists.
• Problem can be reliably reproduced, doesn't happen randomly.
• Problem happens with all files and projects, not only some files or projects.

Additional context

No response

[m-kuhn]

Thanks for the report,

This is already fixed in #738 but not released yet.

We will make sure to have a public release of this before QGIS 4 comes out, which is the first official release based on Qt6.