From 37fd5ffe8e4ac6fc6af1db7db0fd80df75e4d9e6 Mon Sep 17 00:00:00 2001
From: Tim van der Lippe <tvanderlippe@gmail.com>
Date: Wed, 21 Feb 2018 13:04:06 +0100
Subject: [PATCH] Add mixin to automatically detect capitalized HTML attributes

---
 externs/closure-types.js                      | 17 +++-
 lib/utils/attribute-capitalization-mixin.html | 80 +++++++++++++++++++
 test/unit/attribute-capitalization.html       | 58 ++++++++++++++
 .../utils/attribute-capitalization-mixin.d.ts | 47 +++++++++++
 4 files changed, 201 insertions(+), 1 deletion(-)
 create mode 100644 lib/utils/attribute-capitalization-mixin.html
 create mode 100644 test/unit/attribute-capitalization.html
 create mode 100644 types/lib/utils/attribute-capitalization-mixin.d.ts

diff --git a/externs/closure-types.js b/externs/closure-types.js
index 0cabb51658..5159c4d1c2 100644
--- a/externs/closure-types.js
+++ b/externs/closure-types.js
@@ -1374,4 +1374,19 @@ Polymer_ArraySelectorMixin.prototype.select = function(item){};
 * @param {number} idx Index from `items` array to select
 * @return {void}
 */
-Polymer_ArraySelectorMixin.prototype.selectIndex = function(idx){};
\ No newline at end of file
+Polymer_ArraySelectorMixin.prototype.selectIndex = function(idx){};
+/**
+* @interface
+* @extends {Polymer_PropertyEffects}
+*/
+function Polymer_AttributeCapitalization(){}
+/**
+* @override
+* @param {Node} node Node to parse
+* @param {TemplateInfo} templateInfo Template metadata for current template
+* @param {NodeInfo} nodeInfo Node metadata for current template node
+* @param {*} name 
+* @param {*} value 
+* @return {boolean}
+*/
+Polymer_AttributeCapitalization._parseTemplateNodeAttribute = function(node, templateInfo, nodeInfo, name, value){};
\ No newline at end of file
diff --git a/lib/utils/attribute-capitalization-mixin.html b/lib/utils/attribute-capitalization-mixin.html
new file mode 100644
index 0000000000..d3d856789d
--- /dev/null
+++ b/lib/utils/attribute-capitalization-mixin.html
@@ -0,0 +1,80 @@
+<!--
+@license
+Copyright (c) 2017 The Polymer Project Authors. All rights reserved.
+This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
+The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
+The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
+Code distributed by Google as part of the polymer project is also
+subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
+-->
+<link rel="import" href="boot.html">
+<link rel="import" href="mixin.html">
+<link rel="import" href="../mixins/property-effects.html">
+
+<script>
+(function() {
+
+  'use strict';
+
+  const regex = /[A-Z]/;
+
+  /**
+   * Mixin that uses an heuristic to determine the capitalization of HTML
+   * attributes. By default, all attributes are lowercased. However, some
+   * native attributes have capitalization. `Element.attributes` only returns
+   * capitalized attributes if the attribute name is exactly equal to the attribute.
+   * In other words, `viewBox$` will be lowercased to `viewbox$`. Therefore, if
+   * an attribute name still has capitaliation, we use an attribute effect to
+   * update the bindings.
+   *
+   * @mixinFunction
+   * @polymer
+   * @appliesMixin Polymer.PropertyEffects
+   * @memberof Polymer
+   * @summary Class mixin that uses an heuristic to determine the capitalization
+   * of HTML attributes.
+   */
+  Polymer.AttributeCapitalization = Polymer.dedupingMixin(superClass => {
+
+    /**
+     * @constructor
+     * @extends {superClass}
+     * @implements {Polymer_PropertyEffects}
+     * @unrestricted
+     */
+    const base = Polymer.PropertyEffects(superClass);
+
+    /**
+     * @polymer
+     * @mixinClass
+     * @implements {Polymer_PropertyEffects}
+     * @extends {propertyEffectsBase}
+     * @unrestricted
+     */
+    class AttributeCapitalization extends base {
+      /**
+       * Overrides default `PropertyEffects` implementation to automatically
+       * detect capitalized attributes.
+       *
+       * @override
+       * @param {Node} node Node to parse
+       * @param {TemplateInfo} templateInfo Template metadata for current template
+       * @param {NodeInfo} nodeInfo Node metadata for current template node
+       * @return {boolean} `true` if the visited node added node-specific
+       *   metadata to `nodeInfo`
+       * @protected
+       * @suppress {missingProperties} Interfaces in closure do not inherit statics, but classes do
+       */
+      static _parseTemplateNodeAttribute(node, templateInfo, nodeInfo, name, value) {
+        if (regex.test(name)) {
+          node.removeAttribute(name);
+          name = name + '$';
+        }
+        return super._parseTemplateNodeAttribute(node, templateInfo, nodeInfo, name, value);
+      }
+    }
+
+    return AttributeCapitalization;
+  });
+})();
+</script>
diff --git a/test/unit/attribute-capitalization.html b/test/unit/attribute-capitalization.html
new file mode 100644
index 0000000000..f7927a822f
--- /dev/null
+++ b/test/unit/attribute-capitalization.html
@@ -0,0 +1,58 @@
+<!doctype html>
+<!--
+@license
+Copyright (c) 2017 The Polymer Project Authors. All rights reserved.
+This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
+The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
+The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
+Code distributed by Google as part of the polymer project is also
+subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
+-->
+<html>
+<head>
+  <meta charset="utf-8">
+  <script src="../../../webcomponentsjs/webcomponents-lite.js"></script>
+  <script src="../../../web-component-tester/browser.js"></script>
+  <link rel="import" href="../../polymer.html">
+  <link rel="import" href="../../lib/utils/attribute-capitalization-mixin.html">
+</head>
+<body>
+
+  <dom-module id="svg-element">
+    <template>
+      <svg id="svg" viewBox="[[value]]"></svg>
+    </template>
+    <script>
+      class SVGElement extends Polymer.AttributeCapitalization(Polymer.Element) {
+        static get is() { return 'svg-element'; }
+        static get properties() {
+          return {
+            value: {
+              type: String,
+              value: '0 0 50 50'
+            }
+          };
+        }
+      }
+      customElements.define(SVGElement.is, SVGElement);
+    </script>
+  </dom-module>
+
+<script>
+suite('automated attribute capitalization detection', function() {
+  let el;
+
+  setup(function() {
+    el = document.createElement('svg-element');
+    document.body.appendChild(el);
+  });
+
+  teardown(function() {
+    document.body.removeChild(el);
+  });
+
+  test('can handle capitalized HTML attribute', function() {
+    assert.equal(el.$.svg.getAttribute('viewBox'), el.value);
+  });
+});
+</script>
diff --git a/types/lib/utils/attribute-capitalization-mixin.d.ts b/types/lib/utils/attribute-capitalization-mixin.d.ts
new file mode 100644
index 0000000000..0188ffeb3e
--- /dev/null
+++ b/types/lib/utils/attribute-capitalization-mixin.d.ts
@@ -0,0 +1,47 @@
+/**
+ * DO NOT EDIT
+ *
+ * This file was automatically generated by
+ *   https://github.com/Polymer/gen-typescript-declarations
+ *
+ * To modify these typings, edit the source file(s):
+ *   lib/utils/attribute-capitalization-mixin.html
+ */
+
+/// <reference path="boot.d.ts" />
+/// <reference path="mixin.d.ts" />
+/// <reference path="../mixins/property-effects.d.ts" />
+
+declare namespace Polymer {
+
+
+  /**
+   * Mixin that uses an heuristic to determine the capitalization of HTML
+   * attributes. By default, all attributes are lowercased. However, some
+   * native attributes have capitalization. `Element.attributes` only returns
+   * capitalized attributes if the attribute name is exactly equal to the attribute.
+   * In other words, `viewBox$` will be lowercased to `viewbox$`. Therefore, if
+   * an attribute name still has capitaliation, we use an attribute effect to
+   * update the bindings.
+   */
+  function AttributeCapitalization<T extends new (...args: any[]) => {}>(base: T): T & AttributeCapitalizationConstructor & Polymer.PropertyEffectsConstructor & Polymer.TemplateStampConstructor & Polymer.PropertyAccessorsConstructor & Polymer.PropertiesChangedConstructor;
+
+  interface AttributeCapitalizationConstructor {
+    new(...args: any[]): AttributeCapitalization;
+
+    /**
+     * Overrides default `PropertyEffects` implementation to automatically
+     * detect capitalized attributes.
+     *
+     * @param node Node to parse
+     * @param templateInfo Template metadata for current template
+     * @param nodeInfo Node metadata for current template node
+     * @returns `true` if the visited node added node-specific
+     *   metadata to `nodeInfo`
+     */
+    _parseTemplateNodeAttribute(node: Node|null, templateInfo: TemplateInfo|null, nodeInfo: NodeInfo|null, name: any, value: any): boolean;
+  }
+
+  interface AttributeCapitalization {
+  }
+}