From bd750ceebb9008ecc0ed1e541ee9005f6af26302 Mon Sep 17 00:00:00 2001
From: Seth Falco <seth@falco.fun>
Date: Sat, 23 Sep 2023 21:47:04 +0100
Subject: [PATCH] fix(reusePaths): dont reuse id if referenced in href (#1784)

Fixes a bug where the reusePaths plugin would reuse the node ID that
it's optimizing, but that ID was also referenced in a href elsewhere
in the document, so it unintentionally applied the path to other nodes.
---
 plugins/reusePaths.js          | 23 +++++++++++++++----
 test/plugins/reusePaths.06.svg | 40 ++++++++++++++++++++++++++++++++++
 2 files changed, 59 insertions(+), 4 deletions(-)
 create mode 100644 test/plugins/reusePaths.06.svg

diff --git a/plugins/reusePaths.js b/plugins/reusePaths.js
index d1cb53b14..022b1c036 100644
--- a/plugins/reusePaths.js
+++ b/plugins/reusePaths.js
@@ -37,6 +37,13 @@ exports.fn = () => {
    */
   let svgDefs;
 
+  /**
+   * Set of hrefs that reference the id of another node.
+   *
+   * @type {Set<string>}
+   */
+  const hrefs = new Set();
+
   return {
     element: {
       enter: (node, parentNode) => {
@@ -61,13 +68,20 @@ exports.fn = () => {
         ) {
           svgDefs = node;
         }
+
+        if (node.name === 'use') {
+          for (const name of ['href', 'xlink:href']) {
+            const href = node.attributes[name];
+
+            if (href != null && href.startsWith('#') && href.length > 1) {
+              hrefs.add(href.slice(1));
+            }
+          }
+        }
       },
 
       exit: (node, parentNode) => {
         if (node.name === 'svg' && parentNode.type === 'root') {
-          /**
-           * @type {XastElement}
-           */
           let defsTag = svgDefs;
 
           if (defsTag == null) {
@@ -99,7 +113,8 @@ exports.fn = () => {
               };
               delete reusablePath.attributes.transform;
               let id;
-              if (reusablePath.attributes.id == null) {
+              const reusablePathId = reusablePath.attributes.id;
+              if (reusablePathId == null || hrefs.has(reusablePathId)) {
                 id = 'reuse-' + index;
                 index += 1;
                 reusablePath.attributes.id = id;
diff --git a/test/plugins/reusePaths.06.svg b/test/plugins/reusePaths.06.svg
new file mode 100644
index 000000000..a96d550c4
--- /dev/null
+++ b/test/plugins/reusePaths.06.svg
@@ -0,0 +1,40 @@
+Don't remove and reuse the ID of the duplicate path if it's already being linked
+in an href by another node.
+
+===
+
+<svg xmlns="http://www.w3.org/2000/svg"
+  xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="-29.947 60.987 69.975 102.505">
+  <g transform="translate(-59 64)">
+    <g id="b">
+      <path id="a" fill="#000" d="M0 0v1h.5Z" transform="rotate(18 3.157 -.5)"/>
+      <use xlink:href="#a" width="1" height="1" transform="scale(-1 1)"/>
+    </g>
+    <use xlink:href="#b" width="1" height="1" transform="rotate(72)"/>
+    <use xlink:href="#b" width="1" height="1" transform="rotate(-72)"/>
+    <use xlink:href="#b" width="1" height="1" transform="rotate(144)"/>
+    <use xlink:href="#b" width="1" height="1" transform="rotate(-144)"/>
+  </g>
+  <path id="c" fill="#000" d="M0 0v1h.5Z" transform="rotate(18 3.157 -.5)"/>
+  <use xlink:href="#c" width="1" height="1" transform="scale(-1 1)"/>
+</svg>
+
+@@@
+
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="-29.947 60.987 69.975 102.505">
+    <defs>
+        <path id="reuse-0" fill="#000" d="M0 0v1h.5Z"/>
+    </defs>
+    <g transform="translate(-59 64)">
+        <g id="b">
+            <use id="a" transform="rotate(18 3.157 -.5)" xlink:href="#reuse-0"/>
+            <use xlink:href="#a" width="1" height="1" transform="scale(-1 1)"/>
+        </g>
+        <use xlink:href="#b" width="1" height="1" transform="rotate(72)"/>
+        <use xlink:href="#b" width="1" height="1" transform="rotate(-72)"/>
+        <use xlink:href="#b" width="1" height="1" transform="rotate(144)"/>
+        <use xlink:href="#b" width="1" height="1" transform="rotate(-144)"/>
+    </g>
+    <use id="c" transform="rotate(18 3.157 -.5)" xlink:href="#reuse-0"/>
+    <use xlink:href="#c" width="1" height="1" transform="scale(-1 1)"/>
+</svg>