From 4da8b38fee04a15cd814028c6d0ebf69a2b326c2 Mon Sep 17 00:00:00 2001
From: johnkenny54 <45182853+johnkenny54@users.noreply.github.com>
Date: Sat, 6 Jan 2024 06:55:24 -0800
Subject: [PATCH] fix(removeHiddenElems): dont remove node if children have
 referenced id (#1925)

---
 plugins/removeHiddenElems.js          | 26 ++++++++++++++++++--------
 test/plugins/removeHiddenElems.16.svg | 23 +++++++++++++++++++++++
 test/plugins/removeHiddenElems.17.svg | 23 +++++++++++++++++++++++
 test/plugins/removeHiddenElems.18.svg | 23 +++++++++++++++++++++++
 4 files changed, 87 insertions(+), 8 deletions(-)
 create mode 100644 test/plugins/removeHiddenElems.16.svg
 create mode 100644 test/plugins/removeHiddenElems.17.svg
 create mode 100644 test/plugins/removeHiddenElems.18.svg

diff --git a/plugins/removeHiddenElems.js b/plugins/removeHiddenElems.js
index 9713d5c52..995ecff65 100644
--- a/plugins/removeHiddenElems.js
+++ b/plugins/removeHiddenElems.js
@@ -91,6 +91,23 @@ export const fn = (root, params) => {
    */
   let deoptimized = false;
 
+  /**
+   * Nodes can't be removed if they or any of their children have an id attribute that is referenced.
+   * @param {XastElement} node
+   * @returns boolean
+   */
+  function canRemoveNonRenderingNode(node) {
+    if (allReferences.has(node.attributes.id)) {
+      return false;
+    }
+    for (const child of node.children) {
+      if (child.type === 'element' && !canRemoveNonRenderingNode(child)) {
+        return false;
+      }
+    }
+    return true;
+  }
+
   /**
    * @param {XastChild} node
    * @param {XastParent} parentNode
@@ -113,11 +130,6 @@ export const fn = (root, params) => {
       enter: (node, parentNode) => {
         // transparent non-rendering elements still apply where referenced
         if (nonRendering.has(node.name)) {
-          if (node.attributes.id == null) {
-            detachNodeFromParent(node, parentNode);
-            return visitSkip;
-          }
-
           nonRenderedNodes.set(node, parentNode);
           return visitSkip;
         }
@@ -419,9 +431,7 @@ export const fn = (root, params) => {
             nonRenderedNode,
             nonRenderedParent,
           ] of nonRenderedNodes.entries()) {
-            const id = nonRenderedNode.attributes.id;
-
-            if (!allReferences.has(id)) {
+            if (canRemoveNonRenderingNode(nonRenderedNode)) {
               detachNodeFromParent(nonRenderedNode, nonRenderedParent);
             }
           }
diff --git a/test/plugins/removeHiddenElems.16.svg b/test/plugins/removeHiddenElems.16.svg
new file mode 100644
index 000000000..9795db0b9
--- /dev/null
+++ b/test/plugins/removeHiddenElems.16.svg
@@ -0,0 +1,23 @@
+Don't remove non-rendering elements if children have IDs. 
+
+===
+
+<svg xmlns="http://www.w3.org/2000/svg">
+    <rect fill="url(#a)" width="64" height="64"/>
+    <symbol>
+        <linearGradient id="a">
+            <stop offset="5%" stop-color="gold" />
+        </linearGradient>
+    </symbol>
+</svg>
+
+@@@
+
+<svg xmlns="http://www.w3.org/2000/svg">
+    <rect fill="url(#a)" width="64" height="64"/>
+    <symbol>
+        <linearGradient id="a">
+            <stop offset="5%" stop-color="gold"/>
+        </linearGradient>
+    </symbol>
+</svg>
\ No newline at end of file
diff --git a/test/plugins/removeHiddenElems.17.svg b/test/plugins/removeHiddenElems.17.svg
new file mode 100644
index 000000000..ef3557e0a
--- /dev/null
+++ b/test/plugins/removeHiddenElems.17.svg
@@ -0,0 +1,23 @@
+Don't remove used symbols.
+
+===
+
+<svg xmlns="http://www.w3.org/2000/svg">
+    <rect fill="url(#a)" width="64" height="64"/>
+    <g>
+        <linearGradient id="a">
+            <stop offset="5%" stop-color="gold" />
+        </linearGradient>
+    </g>
+</svg>
+
+@@@
+
+<svg xmlns="http://www.w3.org/2000/svg">
+    <rect fill="url(#a)" width="64" height="64"/>
+    <g>
+        <linearGradient id="a">
+            <stop offset="5%" stop-color="gold"/>
+        </linearGradient>
+    </g>
+</svg>
\ No newline at end of file
diff --git a/test/plugins/removeHiddenElems.18.svg b/test/plugins/removeHiddenElems.18.svg
new file mode 100644
index 000000000..ad1bb7f34
--- /dev/null
+++ b/test/plugins/removeHiddenElems.18.svg
@@ -0,0 +1,23 @@
+Preserve <defs> with referenced path.
+
+===
+
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
+    <g id="test-body-content">
+        <defs>
+            <path id="reference" d="M240 1h239v358H240z"/>
+        </defs>
+        <use xlink:href="#reference" id="use" fill="gray" onclick="test(evt)"/>
+    </g>
+</svg>
+
+@@@
+
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
+    <g id="test-body-content">
+        <defs>
+            <path id="reference" d="M240 1h239v358H240z"/>
+        </defs>
+        <use xlink:href="#reference" id="use" fill="gray" onclick="test(evt)"/>
+    </g>
+</svg>