Gutenberg: Can't use the slash inserter in Japanese

[youknowriad]

In #10961 we tried adding support for non-latin languages for the slash inserter. While the issue seems fixed in some languages (Arabic), it's not working as expected in Japanese

Related https://github.com/WordPress/gutenberg/pull/10961#issuecomment-435266404

Steps to reproduce

I see this is closed but I noticed that the issue isn't solved for Japanese. I don't have Windows machine at hand so am explaining this for Mac (Chrome 69.0.3497.100).

1. Open your computer's keyboard settings and add a Japanese keyboard (日本語). Once an additional keyboard is added, you can switch them using ctrl + space keys. If you have another app assigned to the shortcut, use the top bar icon near where your clock is.
2. Set your WordPress language to Japanese.
3. Start a new post.
4. Set your keyboard to English and type / in a blank paragraph block.
5. Switch to Japanese keyboard and type gazou -> hit space bar -> hit enter. You should see the letters 画像 after the /.

Result: I expected to see the image block appear in the search results but it did not.

A. At this point, you can move your cursor between the two letters (画 and 像) using arrow keys. If you hit ← and → once each, you'll see the suggestion pop-up.

B. Also, if you delete the last letter and just leave /画, you'll see suggestions.

C. But just entering the first letter画 by regular writing action (ga -> space bar -> enter) doesn't have the same result as B above.

[youknowriad]

In my testing it worked properly. I don't understand Japanese and this is the first time I had to use a japanese keyboard, so I might have done something wrong but I can't reproduce.

Switch to Japanese keyboard

In this step, MacOS is proposing three different types of keyboards. The one that worked like the instructions is: "Higrana". Not sure if it's related or not.

I'd appreciate if someone with Japanese knowledge could take a look at the issue to validate my findings.

[mcsf]

I can use slash completion in Japanese as well. See screencast:

It's admittedly a little awkward:

• finding the actual slash character requires navigating down the input suggestions, at least when using an American physical keyboard;
• the IME popover and the block suggestions popover are present at the same time, and I need to press Enter to conclude the IME interaction and be able to move up and down the block suggestions.

But it works. @naokomc, for your issue report were you using the latest version of Gutenberg (4.1.1 as of today)?

I'll preemptively close this issue, but feel free to comment and reopen.

[naokomc]

Step 4 seems to be missed in others' test, but I don't think that itself matters.

The difference in my environment I noticed after seeing others' tests is that I have "Live Conversion" option turned off.
e.g. https://www.kuropixel.com/turn-off-japanese-live-conversion/

Google IME in its default state also caused this issue but since I don't have datá for what percentage of Japanese users are not using the IME in the OS's default setting, I can't say that this is a major issue. Will ask Windows users too.

[atachibana]

I tested it on Windows 10 Japanese edition with WordPress 5.0 Beta 3.
It works property with MS-IME and Google IME. /画像 could find image bock. Thank you for the good work!

Just my thought:
But I want to propose to leave the function /image even in Japanese environment, because key combinations of Turn off Japanese -> / -> Turn on Japanese -> 画像 is too much for the shortcut...

[youknowriad]

@atachibana Thanks for the tests

But I want to propose to leave the function /image even in Japanese environment,

Yes, this has been suggested here #11370