Wrong behaviour when correct answer contains special (german) characters

[Dmfama20]

Description
I have the following questiontext

Complete this sentence... [correct ending (richtige Lösung)]

containing the german character "ö".

and this wrong answers

Wrong ending, very wrong ending, not correct ending

To Reproduce
Steps to reproduce the behavior:

1. I create a question as mentioned above and save it
2. I fill the gap by the correct answer and this answer is displayed as wrong

Expected behavior
Correct answers should be displayed as correct

Screenshots

[marcusgreen]

Could you export and attach an xml version of your question

[marcusgreen]

Have you got regular expressions disabled as the characters ( and ) are "special", see
https://docs.moodle.org/402/en/Gapfill_question_type#Disable_Regex

[Dmfama20]

Hi,
here is the xml of the question (I renamed it to *.txt since xml-files not allowed here)
quiz-SF-Gapfill test-20230428-1115.txt

I tried "disableregex" on and off and purged cache when switching on/off. But no changes. The correct answer is still marked wrong.

[marcusgreen]

Thank you for your quick response. Can you confirm that when you change disableregex you are testing the modified version. I just imported your xml and it seemed to work for me. It would be nice if it warned when regular expression characters were used.

[Dmfama20]

I'm not sure what you mean:
1.) I set "disableregex" as true and purge all caches.
2.) I go to the question and edit it.
3.) I save it as a new version.
4.) I start a new preview of the latest version of the question but I remark the same error as before.

Some more details:
Moodle version 4.1.2
qtype_gapfill version 2.136

[marcusgreen]

If you email me at marcusavgreen at gmail dot com I can give you access to a course where we compare how your question example works.

[Dmfama20]

I have sent you an email yesterday....

[Dmfama20]

Any news about that?

[marcusgreen]

I have not worked on it, but your post is a prompt for me to at least start working on some code. I will create a new branch which you can monitor for changes. It would be fairly easy to strip out just the html space character, but I would probably need to strip out other things as well. In an ideal world I would throw up a warning that the text contained invisible things and stop the saving, but I have yet to work out how I would do that. I guess I need to ask around. Thanks for the reminder.

[PhilippImhof]

Could this be related to #106 ?

[marcusgreen]

I think this is a different issue, but it reminds me of a long time plan to put up a warning if the contents of gaps may not make any sense. I was focussing on showing the warning before saving (or preventing saving). But since then I figure I will just show it on reload after saving. Needs to go onto my ToDo list.