Change 656103 had a related patch set uploaded (by Thiemo Kreuz (WMDE); owner: Thiemo Kreuz (WMDE)):
[mediawiki/extensions/CodeMirror@master] Rename our customized matchbrackets addon

https://gerrit.wikimedia.org/r/656103

Change 656119 had a related patch set uploaded (by Thiemo Kreuz (WMDE); owner: Thiemo Kreuz (WMDE)):
[mediawiki/extensions/CodeMirror@master] [WIP] Disable non-matching highlighting via config flag

https://gerrit.wikimedia.org/r/656119

Change 656119 merged by jenkins-bot:
[mediawiki/extensions/CodeMirror@master] Disable non-matching highlighting via config flag

https://gerrit.wikimedia.org/r/656119

I finally understood the incompatibility issue between our mediawiki mode and the matchbrackets addon.

The addon is written in a way that it does not only check if the characters match (e.g. ( and )), it also checks if these two characters have the same style a.k.a. the same CSS class names. You can test this on codemirror.net with code like this:

<script>
function(; //comment)
</script>

This pair of brackets won't match because they have two different styles. This is intentional and fine.

Our problem is that the mediawiki mode uses an empty string for the default black text. This empty string ends in the addon in a line style || null where it is turned into null. This later fails because '' != null.

I don't really get why this || null is there. The value on the left can't be anything but a string or null. The only thing the || does is turning the empty string into null. But why? The only reason to do this is to intentionally not have any bracket matching when a mode does not apply a class name to basic text. But again, why? Most modes do apply a class name even to basic text, they just don't style it (i.e. it's still the default black, but does have a class name for optional styling). In other words: It's not like this distinction understands when text is styled and when not. The distinction is made based on a technical aspect that is not even guaranteed to be user-facing.

The hack we did removed the extra check entirely. This does have two effects:

• In an example like the one above where two brackets have different colors, they will still be highlighted.
• It significantly improves the performance.

I suggest to leave our hack as it is because of the performance implications, but suggest to remove the "|| null" upstream. We can come back and change this later when users complain about unexpected highlighting.

I don't want to change our mediawiki mode to apply a non-empty default style because I suspect this might affect the performance.

Change 656103 merged by jenkins-bot:
[mediawiki/extensions/CodeMirror@master] Rename our customized matchbrackets addon

https://gerrit.wikimedia.org/r/656103