shell "No such file or directory" on variable execution result - sh

Question

some basic function with goal to extract xml var by xpath:
function get_xml_value_from_config_dir {
local src_root=$1
local xpath_expr="//$2/text()"
local path_to_local="$src_root/app/etc/local.xml"
if [ ! -f $path_to_local ]; then echo "Config file not found: $path_to_local"; exit; fi;
echo $("$xmllint --nocdata --xpath '$xpath_expr' $path_to_local")
}
## and then
src_usr=$(get_xml_value_from_config_dir $src_dir username)
gives me
line 34: /usr/bin/xmllint --nocdata --xpath '//username/text()' /tmp/bin/app/etc/local.xml: No such file or directory
why? ( /usr/bin/xmllint exist as well as /tmp/bin/app/etc/local.xml )

Answer 1

It's telling you it can't find the file or directory named
/usr/bin/xmllint --nocdata --xpath '//username/text()' /tmp/bin/app/etc/local.xml
which indeed is unlikely to exist on your system.
Replace
echo $("$xmllint --nocdata --xpath '$xpath_expr' $path_to_local")
with
echo $($xmllint --nocdata --xpath "$xpath_expr" $path_to_local)
Incidentally, that will put all xmllint output on a single line; to avoid that, just use
xmllint --nocdata --xpath "$xpath_expr" $path_to_local