Replacing first occurrence line after first matched line - sed

Question

Let's assume the following XML file:
some text
<addresses>
<something/>
</addresses>
some more text
<addresses xmlns="namespace">
<could be anything/>
</addresses>
some other text
<addresses>
<something else/>
</addresses>
...
I need to replace the first </addresses> following the first <addresses xmlns="namespace"> by </namespace:addresses> so that the file becomes:
some text
<addresses>
<something/>
</addresses>
some more text
<addresses xmlns="namespace">
<could be anything/>
</namespace:addresses>
some other text
<addresses>
<something else/>
</addresses>
...
I am aware of this similar thread, but none of the following solution changes anything:
sed -e '/<addresses xmlns="namespace">/!b' -e ':a' -e "s/<\/namespace:addresses>/<\/addresses>/;t trail" -e 'n;ba' -e ':trail' -e 'n;btrail' file.xml
sed -e "/<addresses xmlns=\"namespace\">/,/./ s/<\/namespace:addresses>/<\/addresses>/" file.xml
sed -e "/<addresses xmlns=\"namespace\">/,/<\/namespace:addresses>/ s/<\/namespace:addresses>/<\/addresses>/" file.xml
For instance:
sed -e "/<addresses xmlns=\"namespace\">/,/./ s/<\/namespace:addresses>/<\/addresses>/" file.xml
some text
<addresses>
<something/>
</addresses>
some more text
<addresses xmlns="namespace">
<could be anything/>
</addresses>
some other text
<addresses>
<something else/>
</addresses>
...
Maybe this issue is linked to the sed I'm using: 4.7-1ubuntu1 on impish/21.10 or even 4.8-1.
Any suggestion?
I'm open to any other tool (perl/awk), the simpler, the better.

Answer 1

It is much easier with perl than with sed:
perl -0777 -i -pe 's~<(addresses)\s+xmlns="namespace">[^<]*(?:<(?!/\1>)[^<]*)*\K</\1>~</namespace:$1>~' file
See the online demo. Details:
<(addresses)\s+xmlns="namespace">[^<]*(?:<(?!/\1>)[^<]*)*\K</\1> - the regex pattern matching
< - a < char
(addresses) - Group 1 ($1): addresses
\s+ - one or more whitespaces
xmlns="namespace"> - a fixed string
[^<]*(?:<(?!/\1>)[^<]*)* - a much faster alternative to (?s:.)*? - basically, matches any text up to a </addresses> string
\K - match reset operator that omits all text matched so far from the current match memory buffer
</\1> - (this is what is finally consumed and will be replaced): </ + Group 1 value (so as not to repeat addresses) + >
</namespace:$1> - the replacement is </namespace: + Group 1 value + >.
It replaces the first occurrence because the -0777 slurps the file into a single multiline text and there is no g flag.
Note the difference between \1 backreference syntax inside the pattern and $1 replacement backreference in the replacement pattern in perl command.
See the online demo:
s=' some text
<addresses>
<something/>
</addresses>
some more text
<addresses xmlns="namespace">
<could be anything/>
</addresses>
some other text
<addresses>
<something else/>
</addresses>
...'
perl -0777 -pe 's~<(addresses)\s+xmlns="namespace">[^<]*(?:<(?!/\1>)[^<]*)*\K</\1>~</namespace:$1>~' <<< "$s"
Output:
some text
<addresses>
<something/>
</addresses>
some more text
<addresses xmlns="namespace">
<could be anything/>
</namespace:addresses>
some other text
<addresses>
<something else/>
</addresses>
...