bug#58718: Incorrect regex in nXML URI check

[Robert Pluim]

>>>>> On Mon, 24 Oct 2022 12:51:30 +0200, Mattias Engdegård 
>>>>> <mattias.engdegard@gmail.com> said:

    Mattias> I concur with the assessment. Your fixes are straightforward and 
have
    Mattias> now been pushed to master.

    Mattias> I also did a quick scan for similar errors (missing backslashes 
before
    Mattias> curly brackets) but found no obvious cases of the same bug in the
    Mattias> Emacs tree. A check could be added to the regexp linter but it's 
hard
    Mattias> to guard against false positives.

    Mattias> Thanks for the report and patch. This code hasn't seen much changes
    Mattias> since it was added to Emacs, so if you find something else to 
improve
    Mattias> you are more than welcome to contribute to further development.

If youʼre [1] looking at the code anyway, there might be opportunities to
use `url-unhex' and similar from 'url-utils.el' rather than
re-implementing the same function in nxml.

Robert

Footnotes:
[1]  For the grammar pedants, of which Emacs appears to have many,
     thatʼs a plural 'you' 😀

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