Parse HTML/XML characters in R - r

Question

I am reading in the following XML as a text file in R:
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE score-partwise PUBLIC
"-//Recordare//DTD MusicXML 3.0 Partwise//EN"
"http://www.musicxml.org/dtds/partwise.dtd">
<score-partwise version="3.0">
<part-list>
<score-part id="P1">
<part-name>Music</part-name>
</score-part>
</part-list>
<part id="P1">
<measure number="1">
<attributes>
<divisions>1</divisions>
<key>
<fifths>0</fifths>
</key>
<time>
<beats>4</beats>
<beat-type>4</beat-type>
</time>
<clef>
<sign>G</sign>
<line>2</line>
</clef>
</attributes>
<note>
<pitch>
<step>C</step>
<octave>4</octave>
</pitch>
<duration>4</duration>
<type>whole</type>
</note>
</measure>
</part>
</score-partwise>
R:
library(readtext)
xml <- readtext("musicxml.txt")$text
I am then trying to render this in Javascript via Shiny by feeding my XML text to a Javascript function. NB: Working outside of R.
shiny::tags$script(paste0('var osmd = new opensheetmusicdisplay.OpenSheetMusicDisplay(\"sheet-music\", {drawingParameters: "compact",
drawPartNames: false, drawMeasureNumbers: false, drawMetronomeMarks: false, drawTitle: false});
var loadPromise = osmd.load(\'',xml,'\');
loadPromise.then(function(){
osmd.render();
});
'))
However, when I concatenate the XML string above, it does not work because characters are escaped, e.g one line:
<note>
I tried using the unescape_xml function here (with and without the tags removed), but this does not solve the problem. It leaves me with:
"Music1044G2C44whole"
So how can I end up with a concatenated string with none of the escaped characters? It must just be a string and not another R object.

Answer 1

You need to wrap the contents of the tag call with shiny::HTML to ensure it is passed unescaped:
shiny::tags$script(shiny::HTML(paste0(
'var osmd = new opensheetmusicdisplay.OpenSheetMusicDisplay(\"sheet-music\",
{ drawingParameters: "compact",
drawPartNames: false,
drawMeasureNumbers: false,
drawMetronomeMarks: false,
drawTitle: false});
var loadPromise = osmd.load(\'',xml,'\');
loadPromise.then(function(){ osmd.render() });')))
Which gives you:
<script>var osmd = new opensheetmusicdisplay.OpenSheetMusicDisplay("sheet-music",
{ drawingParameters: "compact",
drawPartNames: false,
drawMeasureNumbers: false,
drawMetronomeMarks: false,
drawTitle: false});
var loadPromise = osmd.load('<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE score-partwise PUBLIC
"-//Recordare//DTD MusicXML 3.0 Partwise//EN"
"http://www.musicxml.org/dtds/partwise.dtd">
<score-partwise version="3.0">
<part-list>
<score-part id="P1">
<part-name>Music</part-name>
</score-part>
</part-list>
<part id="P1">
<measure number="1">
<attributes>
<divisions>1</divisions>
<key>
<fifths>0</fifths>
</key>
<time>
<beats>4</beats>
<beat-type>4</beat-type>
</time>
<clef>
<sign>G</sign>
<line>2</line>
</clef>
</attributes>
<note>
<pitch>
<step>C</step>
<octave>4</octave>
</pitch>
<duration>4</duration>
<type>whole</type>
</note>
</measure>
</part>
</score-partwise>');
loadPromise.then(function(){ osmd.render() });</script>