polymer/lib/mixins/element-mixin.html

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@license
Copyright (c) 2014 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
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The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
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<link rel="import" href="../utils/boot.html">
<link rel="import" href="../utils/mixin.html">
<link rel="import" href="../utils/case-map.html">
<link rel="import" href="../utils/style-gather.html">
<link rel="import" href="../utils/resolve-url.html">
<link rel="import" href="../elements/dom-module.html">
<link rel="import" href="property-effects.html">

<script>
(function() {
  /**
   * @typedef Object<string, {
   *   value: *,
   *   type: (Function | undefined),
   *   readOnly: (boolean | undefined),
   *   computed: (string | undefined),
   *   reflectToAttribute: (boolean | undefined),
   *   notify: (boolean | undefined),
   *   observer: (string | undefined)
   * }>)
   */
  let PolymerElementProperties; // eslint-disable-line no-unused-vars

  /** @record */
  let PolymerElementConstructor = function(){}; // eslint-disable-line no-unused-vars
  /** @type {(string | undefined)} */
  PolymerElementConstructor.is;
  /** @type {(string | undefined)} */
  PolymerElementConstructor.extends;
  /** @type {(!PolymerElementProperties | undefined)} */
  PolymerElementConstructor.properties;
  /** @type {(!Array<string> | undefined)} */
  PolymerElementConstructor.observers;
  /** @type {(!HTMLTemplateElement | string | undefined)} */
  PolymerElementConstructor.template;

  /**
   * Element class mixin that provides the core API for Polymer's meta-programming
   * features including template stamping, data-binding, attribute deserialization,
   * and property change observation.
   *
   * @polymerMixin
   * @mixes Polymer.PropertyEffects
   * @memberof Polymer
   * @summary Element class mixin that provides the core API for Polymer's
   * meta-programming features.
   */
  Polymer.ElementMixin = Polymer.dedupingMixin(function(base) {

    const polymerElementBase = Polymer.PropertyEffects(base);

    let caseMap = Polymer.CaseMap;

    /**
     * Returns the `properties` object specifically on `klass`. Use for:
     * (1) super chain mixes togther to make `propertiesForClass` which is
     * then used to make `observedAttributes`.
     * (2) properties effects and observers are created from it at `finalize` time.
     * @param {HTMLElement} klass
     * @private
     */
    function ownPropertiesForClass(klass) {
      if (!klass.hasOwnProperty(
        goog.reflect.objectProperty('__ownProperties', klass))) {
        klass.__ownProperties =
          klass.hasOwnProperty(goog.reflect.objectProperty('properties', klass)) ?
          klass.properties : {};
      }
      return klass.__ownProperties;
    }

    /**
     * Returns the `observers` array specifically on `klass`. Use for
     * setting up observers.
     * @param {HTMLElement} klass
     * @private
     */
    function ownObserversForClass(klass) {
      if (!klass.hasOwnProperty(
        goog.reflect.objectProperty('__ownObservers', klass))) {
        klass.__ownObservers =
          klass.hasOwnProperty(goog.reflect.objectProperty('observers', klass)) ?
          klass.observers : [];
      }
      return klass.__ownObservers;
    }

    /**
     * Mixes `props` into `flattenedProps` but upgrades shorthand type
     * syntax to { type: Type}.
     * @param {Object} flattenedProps
     * @param {Object} props
     * @private
     */
    function flattenProperties(flattenedProps, props) {
      for (let p in props) {
        let o = props[p];
        if (typeof o == 'function') {
          o = { type: o };
        }
        flattenedProps[p] = o;
      }
      return flattenedProps;
    }

    /**
     * Returns a flattened list of properties mixed together from the chain of all
     * constructor's `config.properties`. This list is used to create
     * (1) observedAttributes,
     * (2) class property default values
     * @param {HTMLElement} klass
     * @return {PolymerElementProperties}
     * @private
     */
    function propertiesForClass(klass) {
      if (!klass.hasOwnProperty(
        goog.reflect.objectProperty('__classProperties', klass))) {
        klass.__classProperties =
        flattenProperties({}, ownPropertiesForClass(klass));
        let superCtor = Object.getPrototypeOf(klass.prototype).constructor;
        if (superCtor.prototype instanceof PolymerElement) {
          klass.__classProperties = Polymer.mixin(
            Object.create(propertiesForClass(superCtor)),
            klass.__classProperties);
        }
      }
      return klass.__classProperties;
    }

    /**
     * Returns a list of properties with default values.
     * This list is created as an optimization since it is a subset of
     * the list returned from `propertiesForClass`.
     * This list is used in `_initializeProperties` to set property defaults.
     * @param {HTMLElement} klass
     * @return {PolymerElementProperties}
     * @private
     */
    function propertyDefaultsForClass(klass) {
      if (!klass.hasOwnProperty(
        goog.reflect.objectProperty('__classPropertyDefaults', klass))) {
        this.__classPropertyDefaults = null;
        let props = propertiesForClass(klass);
        for (let p in props) {
          let info = props[p];
          if ('value' in info) {
            klass.__classPropertyDefaults = klass.__classPropertyDefaults || {};
            klass.__classPropertyDefaults[p] = info;
          }
        }
      }
      return klass.__classPropertyDefaults;
    }

    /**
     * Returns true if a `klass` has finalized. Called in `ElementClass.finalize()`
     * @param {HTMLElement} klass
     * @private
     */
    function hasClassFinalized(klass) {
      return klass.hasOwnProperty(goog.reflect.objectProperty('__finalized', klass));
    }

    /**
     * Called by `ElementClass.finalize()`. Ensures this `klass` and
     * *all superclasses* are finalized by traversing the prototype chain
     * and calling `klass.finalize()`.
     * @param {HTMLElement} klass
     * @private
     */
    function finalizeClassAndSuper(klass) {
      let proto = klass.prototype;
      let superCtor = Object.getPrototypeOf(proto).constructor;
      if (superCtor.prototype instanceof PolymerElement) {
        superCtor.finalize();
      }
      finalizeClass(klass);
    }

    /**
     * Configures a `klass` based on a staic `klass.config` object and
     * a `template`. This includes creating accessors and effects
     * for properties in `config` and the `template` as well as preparing the
     * `template` for stamping.
     */
    function finalizeClass(klass) {
      klass.__finalized = true;
      let proto = klass.prototype;
      if (klass.hasOwnProperty(
        goog.reflect.objectProperty('is', klass)) && klass.is) {
        Polymer.telemetry.register(proto);
      }
      let props = ownPropertiesForClass(klass);
      if (props) {
        finalizeProperties(proto, props);
      }
      let observers = ownObserversForClass(klass);
      if (observers) {
        finalizeObservers(proto, observers, props);
      }
      // note: create "working" template that is finalized at instance time
      let template = klass.template;
      if (template) {
        if (typeof template === 'string') {
          let t = document.createElement('template');
          t.innerHTML = template;
          template = t;
        } else {
          template = template.cloneNode(true);
        }
        proto._template = template;
      }
    }

    /**
     * Configures a `proto` based on a `properties` object.
     * Leverages `PropertyEffects` to create property accessors and effects
     * supporting, observers, reflecting to attributes, change notification,
     * computed properties, and read only properties.
     * @param {HTMLElement} proto
     * @param {Object} properties
     * @private
     */
    function finalizeProperties(proto, properties) {
      for (let p in properties) {
        createPropertyFromConfig(proto, p, properties[p], properties);
      }
    }

    /**
     * Configures a `proto` based on a `observers` array.
     * Leverages `PropertyEffects` to create observers.
     * @param {HTMLElement} proto
     * @param {Array} observers
     * @private
     */
    function finalizeObservers(proto, observers, dynamicProperties) {
      for (let i=0; i < observers.length; i++) {
        proto._createMethodObserver(observers[i], dynamicProperties);
      }
    }

    /**
     * Creates effects for a property.
     *
     * Note, once a property has been set to
     * `readOnly`, `computed`, `reflectToAttribute`, or `notify`
     * these values may not be changed. For example, a subclass cannot
     * alter these settings. However, additional `observers` may be added
     * by subclasses.
     *
     * @param {string} name Name of the property.
     * @param {*=} info Info object from which to create property effects.
     * Supported keys:
     *
     * * type: {function} type to which an attribute matching the property
     * is deserialized. Note the property is camel-cased from a dash-cased
     * attribute. For example, 'foo-bar' attribute is dersialized to a
     * property named 'fooBar'.
     *
     * * readOnly: {boolean} creates a readOnly property and
     * makes a private setter for the private of the form '_setFoo' for a
     * property 'foo',
     *
     * * computed: {string} creates a computed property. A computed property
     * also automatically is set to `readOnly: true`. The value is calculated
     * by running a method and arguments parsed from the given string. For
     * example 'compute(foo)' will compute a given property when the
     * 'foo' property changes by executing the 'compute' method. This method
     * must return the computed value.
     *
     * * reflectToAttriute: {boolean} If true, the property value is reflected
     * to an attribute of the same name. Note, the attribute is dash-cased
     * so a property named 'fooBar' is reflected as 'foo-bar'.
     *
     * * notify: {boolean} sends a non-bubbling notification event when
     * the property changes. For example, a property named 'foo' sends an
     * event named 'foo-changed' with `event.detail` set to the value of
     * the property.
     *
     * * observer: {string} name of a method that runs when the property
     * changes. The arguments of the method are (value, previousValue).
     *
     * @param {HTMLElement} proto
     * @param {string} name
     * @param {object} info
     * @param {object} props
     * @private
     */
    /* Note: Users may want control over modifying property
    effects via subclassing. For example, a user might want to make a
    reflectToAttribute property not do so in a subclass. We've chosen to
    disable this because it leads to additional complication.
    For example, a readOnly effect generates a special setter. If a subclass
    disables the effect, the setter would fail unexpectedly.
    Based on feedback, we may want to try to make effects more malleable
    and/or provide an advanced api for manipulating them.
    Also consider adding warnings when an effect cannot be changed.
    */
    function createPropertyFromConfig(proto, name, info, allProps) {
      // computed forces readOnly...
      if (info.computed) {
        info.readOnly = true;
      }
      // Note, since all computed properties are readOnly, this prevents
      // adding additional computed property effects (which leads to a confusing
      // setup where multiple triggers for setting a property)
      // While we do have `hasComputedEffect` this is set on the property's
      // dependencies rather than itself.
      if (info.computed  && !proto._hasReadOnlyEffect(name)) {
        proto._createComputedProperty(name, info.computed, allProps);
      }
      if (info.readOnly && !proto._hasReadOnlyEffect(name)) {
        proto._createReadOnlyProperty(name, !info.computed);
      }
      if (info.reflectToAttribute && !proto._hasReflectEffect(name)) {
        proto._createReflectedProperty(name);
      }
      if (info.notify && !proto._hasNotifyEffect(name)) {
        proto._createNotifyingProperty(name);
      }
      // always add observer
      if (info.observer) {
        proto._createPropertyObserver(name, info.observer, allProps[info.observer]);
      }
    }

    /**
     * Configures an element `proto` to function with a given `template`.
     * The element name `is` and extends `ext` must be specified for ShadyCSS
     * style scoping.
     * @param {HTMLElement} proto
     * @param {HTMLTemplateElement} template
     * @param {string} is
     * @param {string} ext
     * @private
     */
    function finalizeTemplate(proto, template, is, ext) {
      // support `include="module-name"`
      let cssText = Polymer.StyleGather.cssFromTemplate(template) +
        Polymer.StyleGather.cssFromModuleImports(is);
      if (cssText) {
        let style = document.createElement('style');
        style.textContent = cssText;
        template.content.insertBefore(style, template.content.firstChild);
      }
      if (window.ShadyCSS) {
        window.ShadyCSS.prepareTemplate(template, is, ext);
      }
      proto._bindTemplate(template, propertiesForClass(proto.constructor));
    }

    /**
     * @polymerMixinClass
     * @unrestricted
     */
    class PolymerElement extends polymerElementBase {

      static get observedAttributes() {
        if (!this.hasOwnProperty(goog.reflect.objectProperty('__observedAttributes', this))) {
          let list = [];
          let properties = propertiesForClass(this);
          for (let prop in properties) {
            list.push(Polymer.CaseMap.camelToDashCase(prop));
          }
          this.__observedAttributes = list;
        }
        return this.__observedAttributes;
      }

      /**
       * Called automatically when the first element instance is created to
       * ensure that class finalization work has been completed.
       * May be called by users to eagerly perform class finalization work
       * prior to the creation of the first element instance.
       * @public
       */
      static finalize() {
        if (!hasClassFinalized(this)) {
          finalizeClassAndSuper(this);
        }
      }

      static get template() {
        if (!this.hasOwnProperty(goog.reflect.objectProperty('_template', this))) {
          this._template = Polymer.DomModule.import(this.is, 'template') ||
            // note: implemented so a subclass can retrieve the super
            // template; call the super impl this way so that `this` points
            // to the superclass.
            Object.getPrototypeOf(this.prototype).constructor.template;
        }
        return this._template;
      }

      constructor() {
        super();
        Polymer.telemetry.instanceCount++;
        // Stamp template
        if (this._template) {
          this.root = this._stampTemplate(this._template);
        } else {
          this.root = this;
        }
      }

      _initializeProperties() {
        this.constructor.finalize();
        // note: finalize template when we have access to `localName` to
        // avoid dependence on `is` for polyfilling styling.
        if (this._template && !this._template.__polymerFinalized) {
          this._template.__polymerFinalized = true;
          finalizeTemplate(this.__proto__, this._template, this.localName);
        }
        super._initializeProperties();
        // apply property defaults...
        let p$ = propertyDefaultsForClass(this.constructor);
        if (!p$) {
          return;
        }
        for (let p in p$) {
          let info = p$[p];
          if (!this._isPropertyPending(p)) {
            var value = typeof info.value == 'function' ?
              info.value.call(this) :
              info.value;
            if (this._hasPropertyEffect(p)) {
              this._setProperty(p, value)
            } else {
              this[p] = value;
            }
          }
        }
      }

      connectedCallback() {
        if (window.ShadyCSS) {
          window.ShadyCSS.styleElement(this);
        }
        this._flushProperties();
      }

      disconnectedCallback() {}

      ready() {
        super.ready();
        if (this._template) {
          this.root = this._attachDom(this.root);
        }
      }

      /**
       * Attach an element's stamped dom to itself. By default,
       * this method creates a `shadowRoot` and adds the dom to it.
       * However, this method may be overridden to allow an element
       * to put its dom in another location.
       *
       * @method _attachDom
       * @throws {Error}
       * @suppress {missingReturn}
       * @param {NodeList} dom to attach to the element.
       * @return {Node} node to which the dom has been attached.
       */
      _attachDom(dom) {
        if (this.attachShadow) {
          if (dom) {
            if (!this.shadowRoot) {
              this.attachShadow({mode: 'open'});
            }
            this.shadowRoot.appendChild(dom);
            return this.shadowRoot;
          }
        } else {
          throw new Error('ShadowDOM not available. ' +
            // TODO(sorvell): move to compile-time conditional when supported
          'Polymer.Element can create dom as children instead of in ' +
          'ShadowDOM by setting `this.root = this;\` before \`ready\`.');
        }
      }

      attributeChangedCallback(name, old, value) {
        if (old !== value) {
          let property = caseMap.dashToCamelCase(name);
          let type = propertiesForClass(this.constructor)[property].type;
          if (!this._hasReadOnlyEffect(property)) {
            this._attributeToProperty(name, value, type);
          }
        }
      }

      /**
       * Update styling for this element
       *
       * @param {Object=} properties
       *  Override styling with an object of properties where the keys are css properties, and the values are strings
       *  Example: `this.updateStyles({'color': 'blue'})`
       *  These properties are retained unless a value of `null` is set.
       */
      updateStyles(properties) {
        if (window.ShadyCSS) {
          window.ShadyCSS.styleSubtree(this, properties);
        }
      }

      /**
       * Rewrites a given URL relative to a base URL. The base URL defaults to
       * the original location of the document containing the `dom-module` for
       * this element. This method will return the same URL before and after
       * bundling.
       *
       * @param {string} url URL to resolve.
       * @param {string=} base Optional base URL to resolve against, defaults
       * to the element template's ownerDocument baseURI.
       * @return {string} Rewritten URL relative to the import
       */
      resolveUrl(url, base) {
        if (!base) {
          const module = Polymer.DomModule.import(this.constructor.is);
          base = module ? module.assetpath : document.baseURI;
        }
        return Polymer.ResolveUrl.resolveUrl(url, base);
      }

    }

    return PolymerElement;
  });

  // telemetry
  Polymer.telemetry = {
    instanceCount: 0,
    registrations: [],
    _regLog: function(prototype) {
      console.log('[' + prototype.is + ']: registered')
    },
    register: function(prototype) {
      this.registrations.push(prototype);
      Polymer.log && this._regLog(prototype);
    },
    dumpRegistrations: function() {
      this.registrations.forEach(this._regLog);
    }
  };

  Polymer.updateStyles = function(props) {
    if (window.ShadyCSS) {
      window.ShadyCSS.styleDocument(props);
    }
  };

})();
</script>