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。