Leftright does not use buildGroup

As far as I see, commands in delimsizing.js does not utilize buildGroup and build HTML with own functions from delimiter.js. I believe this prevents clean implementation of #835, creates bugs in PRs like #1698, and eventually breaks #809. Handlers unwrapping child delimiter are a part of the problem too (I mean delim: delim.text instead of delim: delim + further buildGroup(delim)).

[KazimirPodolski]

This issue seems to be super specific to one use-case.

[KazimirPodolski]

Sorry I wasn’t specific enought and obfuscated the problem. Yes, inner expression is fine, but the problem is left and right delimiters themselves: \\left and \\right both have delim which is normal tree node but it is being “unwrapped” (leftright handler returns only the symbol instead of the whole node) and htmlBuilder uses delimiter.leftRightDelim which (I believe) does not call buildGroup (because it has no group at all due to unwrapping).

So, the one who wants to attach some data to \\left( or \\right) is unable to do so because data from nodes for ( or ) is not used.