Bug Report: First character is duplicated when typing Japanese with IME

[yuuyaku]

Describe the bug

When using a Japanese Input Method Editor (IME) in the Text editor, the first alphabetical character of a romanized input is incorrectly duplicated before the converted Japanese character appears. This only seems to happen at the beginning of a line.

To Reproduce

Steps to reproduce the behavior:

1. Open any file in the Nextcloud Text editor.
2. Switch the input method to a Japanese IME (e.g., Microsoft IME or Google Japanese Input).
3. Place the cursor at the beginning of a new line.
4. Attempt to type a Japanese word in romaji. For example, type "ka".
5. As another example, type "ai".

Expected behavior

• When I type "ka", the editor should correctly process the input and show "か" after conversion.
• When I type "ai", the editor should show "あい" after conversion.

Actual behavior

• When I type "k" followed by "a", the editor displays "kか". The first letter "k" is duplicated.
• When I type "a" followed by "i", the editor displays "ああい". The first letter "a" is duplicated.

This issue makes it very difficult to type documents in Japanese.

Environment

• Nextcloud version: [Nextcloud Hub 10](31.0.9)
• Text app version: 5.0.0
• Browser and version: Chrome 141.0.7390.76
• Operating system: Windows 11
• IME (Input Method Editor): Google Japanese Input

[juliusknorr]

Thanks for reporting.

I would be curious if this is also an issue in the demo editors at
https://tiptap.dev/
https://prosemirror.net/

In the past I had seen some of those mostly related to bugs in the contenteditable elements.

[yuuyaku]

@juliusknorr
Thanks for the links. I've checked them both.

The issue does not occur on either tiptap.dev or prosemirror.net. Japanese input works as expected on those sites.

[xuhaida76]

Just updated my nextcloud from 31.0.4 to 31.0.9. Similar issue happened when using Chinese input method (firefox 144.0, text version 5.0.0）：
Expected behavior

When I type "ka", the editor should correctly process the input and show "卡" after conversion.
When I type "ai", the editor should show "爱" after conversion.

Actual behavior

When I type "k" followed by "a", the editor displays "k", no Chinese shows.
When I type "a" followed by "i", the editor displays "a"，no Chinese shows .

[xuhaida76]

I tried in my tablet （android）by edge ，the behavor is correct。

[jpurdy647]

I have the same issue in the android app, just opened an issue for it

[mejo-]

Thanks for the report and detailed description!

I was able to reproduce the issue by installing and configuring fcitx5 on my Linux system.

It's reproducible on our latest development branch, i.e. unfortunately the upgrade to Tiptap v3 didn't fix the issue.