From 5a0bfb3ee3dc88d9ca99fe6572cea0079dc86f69 Mon Sep 17 00:00:00 2001
From: Bogdan Chadkin <trysound@yandex.ru>
Date: Sun, 22 Aug 2021 13:11:03 +0300
Subject: [PATCH] [new plugin] remove-xlink-ns

Ref https://github.com/svg/svgo/pull/1508

The new plugin removes xmlns:xlink from <svg> and replaces xlink:href
with href attribute.

xlink namespace is obsolete in SVG 2. Href attribute is recommended
replacement to xlink:href.

This plugin will be enabled by default in SVGO 3.

See https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/href
---
 plugins/plugins.js                  |  1 +
 plugins/remove-xlink-ns.js          | 33 +++++++++++++++++++++++++++++
 test/plugins/remove-xlink-ns.01.svg | 26 +++++++++++++++++++++++
 3 files changed, 60 insertions(+)
 create mode 100644 plugins/remove-xlink-ns.js
 create mode 100644 test/plugins/remove-xlink-ns.01.svg

diff --git a/plugins/plugins.js b/plugins/plugins.js
index 409e07b11..4d0be8fcc 100644
--- a/plugins/plugins.js
+++ b/plugins/plugins.js
@@ -4,6 +4,7 @@
 exports['preset-default'] = require('./preset-default.js');
 
 // builtin plugins
+exports['remove-xlink-ns'] = require('./remove-xlink-ns.js');
 exports.addAttributesToSVGElement = require('./addAttributesToSVGElement.js');
 exports.addClassesToSVGElement = require('./addClassesToSVGElement.js');
 exports.cleanupAttrs = require('./cleanupAttrs.js');
diff --git a/plugins/remove-xlink-ns.js b/plugins/remove-xlink-ns.js
new file mode 100644
index 000000000..2bce38e2d
--- /dev/null
+++ b/plugins/remove-xlink-ns.js
@@ -0,0 +1,33 @@
+'use strict';
+
+exports.name = 'remove-xlink-ns';
+exports.type = 'visitor';
+exports.active = false;
+exports.description =
+  'removes xmlns:xlink and replaces xlink:href with href attribute';
+
+/**
+ * removes xmlns:xlink from <svg> and replaces xlink:href with href attribute
+ *
+ * xlink namespace is obsolete in SVG 2. Href attribute is recommended
+ * replacement to xlink:href.
+ *
+ * https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/href
+ *
+ * @type {import('../lib/types').Plugin<void>}
+ */
+exports.fn = () => {
+  return {
+    element: {
+      enter: (node) => {
+        if (node.attributes['xmlns:xlink'] != null) {
+          delete node.attributes['xmlns:xlink'];
+        }
+        if (node.attributes['xlink:href'] != null) {
+          node.attributes['href'] = node.attributes['xlink:href'];
+          delete node.attributes['xlink:href'];
+        }
+      },
+    },
+  };
+};
diff --git a/test/plugins/remove-xlink-ns.01.svg b/test/plugins/remove-xlink-ns.01.svg
new file mode 100644
index 000000000..94d262bc5
--- /dev/null
+++ b/test/plugins/remove-xlink-ns.01.svg
@@ -0,0 +1,26 @@
+Remove xmlns:xlink and replace xlink:href with href attribute
+
+===
+
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 348.61 100">
+  <defs>
+    <linearGradient id="a" x1="263.36" y1="14.74" x2="333.47" y2="84.85" gradientUnits="userSpaceOnUse">
+      <stop offset="0" stop-color="#45afe4"/>
+      <stop offset="1" stop-color="#364f9e"/>
+    </linearGradient>
+    <linearGradient id="b" x1="262.64" y1="15.46" x2="332.75" y2="85.57" xlink:href="#a"/>
+  </defs>
+</svg>
+
+@@@
+
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 348.61 100">
+    <defs>
+        <linearGradient id="a" x1="263.36" y1="14.74" x2="333.47" y2="84.85" gradientUnits="userSpaceOnUse">
+            <stop offset="0" stop-color="#45afe4"/>
+            <stop offset="1" stop-color="#364f9e"/>
+        </linearGradient>
+        <linearGradient id="b" x1="262.64" y1="15.46" x2="332.75" y2="85.57" href="#a"/>
+    </defs>
+</svg>
+