just iterate through alldefs

plugins/removeHiddenElems.js

@@ -80,13 +80,6 @@ exports.fn = (root, params) => {
    */
   const allDefs = new Map();
 
-  /**
-   * Defs that may have had their children removed.
-   *
-   * @type {Set<XastParent>}
-   */
-  const affectedDefs = new Set();
-
   /**
    * @type {Map<string, Array<{node: XastElement, parentNode: XastParent }>>}
    */
@@ -102,11 +95,13 @@ exports.fn = (root, params) => {
    * @param {XastParent} parentNode
    */
   function removeElement(node, parentNode) {
-    if (parentNode.type === 'element' && parentNode.name === 'defs') {
-      affectedDefs.add(parentNode);
-      if (node.type === 'element' && node.attributes.id != null) {
-        removedDefIds.add(node.attributes.id);
-      }
+    if (
+      node.type === 'element' &&
+      node.attributes.id != null &&
+      parentNode.type === 'element' &&
+      parentNode.name === 'defs'
+    ) {
+      removedDefIds.add(node.attributes.id);
     }
 
     detachNodeFromParent(node, parentNode);
@@ -432,9 +427,8 @@ exports.fn = (root, params) => {
         }
 
         // Remove empty defs
-        for (const node of affectedDefs) {
+        for (const [node, parentNode] of allDefs.entries()) {
           if (node.children.length === 0) {
-            const parentNode = allDefs.get(node);
             detachNodeFromParent(node, parentNode);
           }
         }