Marker tags removed despite being used

[kv-bh]

Simple optimize command can result in markers being removed:
svgo -i input.svg -o output.svg

Input file:

<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100">
  <style>
.line {
  fill: none;
  stroke: #f00;
  stroke-width: 4px;
  marker-end: url(#arrow);
}
#arrow {}
  </style>
  <defs>
    <marker id="arrow" class="arrow" overflow="visible" markerHeight="1" markerWidth="1" orient="auto-start-reverse" preserveAspectRatio="xMidYMid" viewBox="0 0 1 1">
      <path d="M-3-3 0 0l-3 3"/>
    </marker>
  </defs>
  <path d="M 0 50 H 100" class="line"/>
</svg>

Output file:

<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100"><path d="M0 50h100" style="fill:none;stroke:red;stroke-width:4px;marker-end:url(#arrow)"/></svg>

Note that the arrow marker is missing in the output.

In the input file, if #arrow {} is either removed or changed to .arrow {}, the problem doesn't occur.

SVGO 3.3.2
Node 20.10.0

[johnkenny54]

SVGO doesn't handle <style> elements well. I've been working on a version that addresses some of the limitations of SVGO, at https://www.npmjs.com/package/svgo-ll

svgo-ll keeps the <marker> element, though I did notice that it fails to delete class="line" (which doesn't cause any display problems, but it should be removed).