[Bug Report]: diff tool error while processing space between general and multibytes characters

[johnroyer]

Describe the Bug

Diff tool can not work correctly if add/delete space in general character and multibytes characters.

Steps to Reproduce

1. Create a page
2. copy and paste this string: test測試
3. Save page. (revision 1)
4. Edit page
5. Add a space between the words. New string will be: test 測試
6. Save page. (revision 2)
7. Click Revision of page details.
8. Click Changes on the latest revision.
9. Diff tool show some un-expect digits:

Expected Behaviour

Diff tool should show spaces only.

Screenshots or Additional Context

Error WILL occur if and if the add / delete space between general character and multibyte character.

---

The error will NOT occur on this conditions:

• New space between general characters. Example: unittest to unit test.
• New space between multibyte characters. Example: 你好 to 你 好.

Exact BookStack Version

21.12

PHP Version

7.4.27

Hosting Environment

• Ubuntu 20.04.3 LTS
• Nginx 1.18.0 (reverse proxy)
• PHP-fpm 7.4.27

[ssddanbrown]

Thanks for reporting @johnroyer. Could confirm this on my setup.

I maintain the diff handling as a separate project.
I made some updates to handle the provided scenario: ssddanbrown/HtmlDiff@4894499...v1.0.2
Needed to add manual multi-byte handling since using PHP multi-byte functions would end up exponentially slower.

I've updated the version of the library BookStack uses so this should be fixed in the next patch release. Will therefore close this off.

[johnroyer]

Fix confirmed in v21.12.4 . Everything goes well.
Thanks for helping.