Factoring improvements around attribute serialize/deserialize

lib/mixins/element-mixin.html

@@ -283,7 +283,7 @@
        * @param {Object} dynamicFns Object containing keys for any properties
        *   that are functions and should trigger the effect when the function
        *   reference is changed
-       * @private
+       * @protected
        */
       static createObservers(observers, dynamicFns) {
         const proto = this.prototype;
@@ -564,7 +564,7 @@
        */
       attributeChangedCallback(name, old, value) {
         if (old !== value) {
-          let property = caseMap.dashToCamelCase(name);
+          let property = this._attributeForProperty(name);
           if (!this._hasReadOnlyEffect(property)) {
             super.attributeChangedCallback(name, old, value);
           }

lib/mixins/properties-changed.html

@@ -56,6 +56,7 @@
         /**
          * Creates property accessors for the given property names.
          * @param {Object} props Object whose keys are names of accessors.
+         * @protected
          */
         static createProperties(props) {
           const proto = this.prototype;
@@ -88,16 +89,16 @@
           }
           if (!this.__dataHasAccessor[property]) {
             this.__dataHasAccessor[property] = true;
-            this._generatePropertyAccessor(property, readOnly);
+            this._definePropertyAccessor(property, readOnly);
           }
         }
 
         /**
-         * Generates a property accessor for the given property.
+         * Defines a property accessor for the given property.
          * @param {string} property Name of the property
          * @param {boolean=} readOnly When true, no setter is created
          */
-        _generatePropertyAccessor(property, readOnly) {
+         _definePropertyAccessor(property, readOnly) {
           Object.defineProperty(this, property, {
             /* eslint-disable valid-jsdoc */
             /** @this {PropertiesChanged} */
@@ -416,14 +417,21 @@
          *
          * This method is called when reading HTML attribute values to
          * JS properties.  Users may override this method to provide
-         * deserialization for custom `type`s.
+         * deserialization for custom `type`s. The given `type` is executed
+         * as a function with the value as an argument. The `Boolean` `type`
+         * is specially handled such that an empty string returns true.
          *
          * @param {?string} value Value to deserialize.
          * @param {*=} type Type to deserialize the string to.
          * @return {*} Typed value deserialized from the provided string.
          */
         _deserializeValue(value, type) {
-          return typeof type == 'function' ? type(value) : value;
+          switch (type) {
+            case Boolean:
+              return (value !== null);
+            default:
+              return typeof type == 'function' ? type(value) : value;
+          }
         }
 
         /**

lib/mixins/properties-mixin.html

@@ -42,28 +42,25 @@
      */
     const base = Polymer.PropertiesChanged(superClass);
 
-    function BooleanAttribute(value) {
-      return value !== null;
-    }
-
     /**
      * Mixes `moreProps` into `props` but upgrades shorthand type
      * syntax to { type: Type}.
      *
-     * @param {Object} props Bag to collect flattened properties into
-     * @param {Object} moreProps Bag of properties to add to `props`
-     * @return {Object} The input `props` bag
+     * @param {Object} props Properties to normalize
+     * @return {Object} Copy of input `props` with normalized properties that
+     * are in the form {type: Type}
      * @private
      */
-    function mixProperties(props, moreProps) {
-      for (let p in moreProps) {
-        let o = moreProps[p];
+    function normalizeProperties(props) {
+      const output = {};
+      for (let p in props) {
+        let o = props[p];
         if (typeof o == 'function') {
           o = { type: o };
         }
-        props[p] = o;
+        output[p] = o;
       }
-      return props;
+      return output;
     }
 
     /**
@@ -93,7 +90,7 @@
       if (!ctor.hasOwnProperty(
         JSCompiler_renameProperty('__ownProperties', ctor))) {
         const props = ctor.properties;
-        ctor.__ownProperties = props ? mixProperties({}, props) : null;
+        ctor.__ownProperties = props ? normalizeProperties(props) : null;
       }
       return ctor.__ownProperties;
     }

lib/mixins/property-accessors.html

@@ -204,21 +204,6 @@
         }
       }
 
-      /**
-       * Overrides PropertiesChanged implementation to calls the
-       * `_serializeValue` method to convert the typed value to a string.
-       * If the `_serializeValue` method returns `undefined`,
-       * the attribute will be removed (this is the default for boolean
-       * type `false`).
-       *
-       * @param {Element} node Element to set attribute to.
-       * @param {*} value Value to serialize.
-       * @param {string} attribute Attribute name to serialize to.
-       */
-      _valueToNodeAttribute(node, value, attribute) {
-        super._valueToNodeAttribute(node, this._serializeValue(value), attribute);
-      }
-
       /**
        * Overrides PropertiesChanged implemention to serialize objects as JSON.
        *
@@ -265,22 +250,13 @@
          */
         let outValue;
         switch (type) {
-          case Number:
-            outValue = Number(value);
-            break;
-
-          case Boolean:
-            outValue = (value !== null);
-            break;
-
           case Object:
             try {
               outValue = JSON.parse(/** @type {string} */(value));
             } catch(x) {
               // allow non-JSON literals like Strings and Numbers
             }
             break;
-
           case Array:
             try {
               outValue = JSON.parse(/** @type {string} */(value));
@@ -289,17 +265,10 @@
               console.warn(`Polymer::Attributes: couldn't decode Array as JSON: ${value}`);
             }
             break;
-
-          case Date:
-            outValue = new Date(value);
-            break;
-
-          case String:
           default:
-            outValue = value;
+            outValue = super._deserializeValue(value, type);
             break;
         }
-
         return outValue;
       }
       /* eslint-enable no-fallthrough */
@@ -318,9 +287,9 @@
        * for the values to take effect.
        * @protected
        */
-      _generatePropertyAccessor(property, readOnly) {
+       _definePropertyAccessor(property, readOnly) {
         saveAccessorValue(this, property);
-        super._generatePropertyAccessor(property, readOnly);
+        super._definePropertyAccessor(property, readOnly);
       }
 
       /**