IME input causes significant delay or inconsistent behavior in insert mode

[s-kai273]

Describe the bug
When using an IME (e.g. for Japanese input) in insert mode, there is a noticeable delay between confirming a composition (e.g. pressing Enter to finalize a phrase) and the text actually appearing in the editor.
The confirmed input does appear correctly, but there is a perceptible lag that makes the experience feel slow and unnatural.

To Reproduce
Steps to reproduce the behavior:

1. Open a file in VS Code with the VSCodeVim extension enabled
2. Switch to insert mode (i)
3. Use a Japanese IME (e.g. Google Japanese Input, Mozc, Microsoft IME)
4. Type a word like konnichiwa to start composition (こんにちは appears as candidate)
5. Press Enter to confirm the composition
6. Observe that the confirmed text appears with a noticeable delay, rather than instantly

Expected behavior
The confirmed text (e.g. こんにちは) should appear in the editor immediately after pressing Enter to finalize the IME composition, without any perceptible delay.
Input via IME should feel as responsive as in the default VS Code editor.

Screenshots

Environment (please complete the following information):

• Extension (VsCodeVim) version: 1.30.1
• VSCode version: 1.102.1
• OS: Linux Mint
• IME: Mozc (Japanese)

[s-kai273]

I’ve identified the root cause of the issue.

When users input text using an IME, the compositionEnd event is triggered.
At that point, the handleMultipleKeyEvents method of ModeHandler is called with the composed text split into individual characters.
As a result, await vscode.commands.executeCommand('default:type', { text }) is executed once for each character, inside handleMultipleKeyEvents.
This behavior causes a noticeable delay, since default:type is called multiple times unnecessarily.

However, VSCode natively handles IME input by calling default:type once with the full composition text, which is much more efficient.
I’ve proposed a fix and submitted a PR to address this:
#9713

Please take a look. Thanks in advance!