removeUnusedNS plugin doesn't remove unused namespaces declared on non-svg nodes

[alexjlockwood]

For example:

$ svgo --pretty -o - -s  '<svg 
      xmlns="http://www.w3.org/2000/svg"
      xmlns:firstunused="http://first-unused-namespace.com">
      <path xmlns:secondunused="http://second-unused-namespace.com"
          d="M0 0l100 100" />
  </svg>'

results in:

<svg xmlns="http://www.w3.org/2000/svg">
    <path xmlns:secondunused="http://second-unused-namespace.com" d="M0 0l100 100"/>
</svg>

I would expect that the unused namespace declared on the path element would be removed in this scenario.

[GreLI]

The plugin removes only known namespaces like editor-spamming ones.

[alexjlockwood]

Still, it doesn't seem like the plugin would currently remove these "known" namespaces if they are declared on non-SVG nodes, right?

The reason I say this is because when I look at the source code, I notice that the namespaces are currently only collected while iterating over the root SVG node.

[piuccio]

Just stumbled upon this, somehow I ended up with an SVG that looks like this

<?xml version="1.0"?>
<svg width="160" height="70" xmlns="http://www.w3.org/2000/svg" xmlns:svg="http://www.w3.org/2000/svg" xmlns:se="http://svg-edit.googlecode.com" xmlns:xlink="http://www.w3.org/1999/xlink">
 <!-- Created with SVG-edit - https://github.com/SVG-Edit/svgedit-->
 <defs>
  <symbol height="70" id="svg_2" width="140" xmlns="http://www.w3.org/2000/svg" xmlns:svg="http://www.w3.org/2000/svg">

Notice the xmlns and xmlns:svg on the nested symbol

Would be great if the plugin was able to remove it.

The linked PR seems to be stale, any chance someone could have a look?