property-effects.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
-->


<link rel="import" href="../utils/boot.html">
<link rel="import" href="../utils/mixin.html">
<link rel="import" href="../utils/path.html">
<!-- for notify, reflect -->
<link rel="import" href="../utils/case-map.html">
<link rel="import" href="property-accessors.html">
<!-- for annotated effects -->
<link rel="import" href="template-stamp.html">


<script>
(function() {

  'use strict';

  /** @const {Object} */
  const CaseMap = Polymer.CaseMap;

  // Monotonically increasing unique ID used for de-duping effects triggered
  // from multiple properties in the same turn
  let dedupeId = 0;

  /**
   * Property effect types; effects are stored on the prototype using these keys
   * @enum {string}
   */
  const TYPES = {
    COMPUTE: '__computeEffects',
    REFLECT: '__reflectEffects',
    NOTIFY: '__notifyEffects',
    PROPAGATE: '__propagateEffects',
    OBSERVE: '__observeEffects',
    READ_ONLY: '__readOnly'
  }

  /**
   * @typedef {{
   * name: (string | undefined),
   * structured: (boolean | undefined),
   * wildcard: (boolean | undefined)
   * }}
   */
  let DataTrigger; //eslint-disable-line no-unused-vars

  /**
   * @typedef {{
   * info: ?,
   * trigger: (!DataTrigger | undefined),
   * fn: (!Function | undefined)
   * }}
   */
  let DataEffect; //eslint-disable-line no-unused-vars

  let PropertyEffectsType; //eslint-disable-line no-unused-vars

  /**
   * Ensures that the model has an own-property map of effects for the given type.
   * The model may be a prototype or an instance.
   *
   * Property effects are stored as arrays of effects by property in a map,
   * by named type on the model. e.g.
   *
   *   __computeEffects: {
   *     foo: [ ... ],
   *     bar: [ ... ]
   *   }
   *
   * If the model does not yet have an effect map for the type, one is created
   * and returned.  If it does, but it is not an own property (i.e. the
   * prototype had effects), the the map is deeply cloned and the copy is
   * set on the model and returned, ready for new effects to be added.
   *
   * @param {Object} model Prototype or instance
   * @param {string} type Property effect type
   * @return {Object} The own-property map of effects for the given type
   * @private
   */
  function ensureOwnEffectMap(model, type) {
    let effects = model[type];
    if (!effects) {
      effects = model[type] = {};
    } else if (!model.hasOwnProperty(type)) {
      effects = model[type] = Object.create(model[type]);
      for (let p in effects) {
        let protoFx = effects[p];
        let instFx = effects[p] = Array(protoFx.length);
        for (let i=0; i<protoFx.length; i++) {
          instFx[i] = protoFx[i];
        }
      }
    }
    return effects;
  }

  // -- effects ----------------------------------------------

  /**
   * Runs all effects of a given type for the given set of property changes
   * on an instance.
   *
   * @param {!PropertyEffectsType} inst The instance with effects to run
   * @param {Object} effects Object map of property-to-Array of effects
   * @param {Object} props Bag of current property changes
   * @param {Object=} oldProps Bag of previous values for changed properties
   * @param {boolean=} hasPaths True with `props` contains one or more paths
   * @param {*=} extraArgs Additional metadata to pass to effect function
   * @return {boolean} True if an effect ran for this property
   * @private
   */
  function runEffects(inst, effects, props, oldProps, hasPaths, extraArgs) {
    if (effects) {
      let ran = false;
      let id = dedupeId++;
      for (let prop in props) {
        if (runEffectsForProperty(inst, effects, id, prop, props, oldProps, hasPaths, extraArgs)) {
          ran = true;
        }
      }
      return ran;
    }
    return false;
  }

  /**
   * Runs a list of effects for a given property.
   *
   * @param {!PropertyEffectsType} inst The instance with effects to run
   * @param {Object} effects Object map of property-to-Array of effects
   * @param {number} dedupeId Counter used for de-duping effects
   * @param {string} prop Name of changed property
   * @param {*} props Changed properties
   * @param {*} oldProps Old properties
   * @param {boolean=} hasPaths True with `props` contains one or more paths
   * @param {*=} extraArgs Additional metadata to pass to effect function
   * @return {boolean} True if an effect ran for this property
   * @private
   */
  function runEffectsForProperty(inst, effects, dedupeId, prop, props, oldProps, hasPaths, extraArgs) {
    let ran = false;
    let rootProperty = hasPaths ? Polymer.Path.root(prop) : prop;
    let fxs = effects[rootProperty];
    if (fxs) {
      for (let i=0, l=fxs.length, fx; (i<l) && (fx=fxs[i]); i++) {
        if ((!fx.info || fx.info.lastRun !== dedupeId) &&
            (!hasPaths || pathMatchesTrigger(prop, fx.trigger))) {
          if (fx.info) {
            fx.info.lastRun = dedupeId;
          }
          fx.fn(inst, prop, props, oldProps, fx.info, hasPaths, extraArgs);
          ran = true;
        }
      }
    }
    return ran;
  }

  /**
   * Determines whether a property/path that has changed matches the trigger
   * criteria for an effect.  A trigger is a descriptor with the following
   * structure, which matches the descriptors returned from `parseArg`.
   * e.g. for `foo.bar.*`:
   * ```
   * trigger: {
   *   name: 'a.b',
   *   structured: true,
   *   wildcard: true
   * }
   * ```
   * If no trigger is given, the path is deemed to match.
   *
   * @param {string} path Path or property that changed
   * @param {DataTrigger} trigger Descriptor
   * @return {boolean} Whether the path matched the trigger
   */
  function pathMatchesTrigger(path, trigger) {
    if (trigger) {
      let triggerPath = trigger.name;
      return (triggerPath == path) ||
        (trigger.structured && Polymer.Path.isAncestor(triggerPath, path)) ||
        (trigger.wildcard && Polymer.Path.isDescendant(triggerPath, path));
    } else {
      return true;
    }
  }

  /**
   * Implements the "observer" effect.
   *
   * Calls the method with `info.methodName` on the instance, passing the
   * new and old values.
   *
   * @param {!PropertyEffectsType} inst The instance the effect will be run on
   * @param {string} property Name of property
   * @param {Object} props Bag of current property changes
   * @param {Object} oldProps Bag of previous values for changed properties
   * @param {?} info Effect metadata
   * @private
   */
  function runObserverEffect(inst, property, props, oldProps, info) {
    let fn = inst[info.methodName];
    let changedProp = info.property;
    if (fn) {
      fn.call(inst, inst.__data[changedProp], oldProps[changedProp]);
    } else if (!info.dynamicFn) {
      console.warn('observer method `' + info.methodName + '` not defined');
    }
  }

  /**
   * Runs "notify" effects for a set of changed properties.
   *
   * This method differs from the generic `runEffects` method in that it
   * will dispatch path notification events in the case that the property
   * changed was a path and the root property for that path didn't have a
   * "notify" effect.  This is to maintain 1.0 behavior that did not require
   * `notify: true` to ensure object sub-property notifications were
   * sent.
   *
   * @param {!PropertyEffectsType} inst The instance with effects to run
   * @param {Object} notifyProps Bag of properties to notify
   * @param {Object} props Bag of current property changes
   * @param {Object} oldProps Bag of previous values for changed properties
   * @param {boolean} hasPaths True with `props` contains one or more paths
   * @private
   */
  function runNotifyEffects(inst, notifyProps, props, oldProps, hasPaths) {
    // Notify
    let fxs = inst[TYPES.NOTIFY];
    let notified;
    let id = dedupeId++;
    // Try normal notify effects; if none, fall back to try path notification
    for (let prop in notifyProps) {
      if (notifyProps[prop]) {
        if (fxs && runEffectsForProperty(inst, fxs, id, prop, props, oldProps, hasPaths)) {
          notified = true;
        } else if (hasPaths && notifyPath(inst, prop, props)) {
          notified = true;
        }
      }
    }
    // Flush host if we actually notified and host was batching
    // And the host has already initialized clients; this prevents
    // an issue with a host observing data changes before clients are ready.
    let host;
    if (notified && (host = inst.__dataHost) && host._invalidateProperties) {
      host._invalidateProperties();
    }
  }

  /**
   * Dispatches {property}-changed events with path information in the detail
   * object to indicate a sub-path of the property was changed.
   *
   * @param {!PropertyEffectsType} inst The element from which to fire the event
   * @param {string} path The path that was changed
   * @param {Object} props Bag of current property changes
   * @return {boolean} Returns true if the path was notified
   * @private
   */
  function notifyPath(inst, path, props) {
    let rootProperty = Polymer.Path.root(path);
    if (rootProperty !== path) {
      let eventName = Polymer.CaseMap.camelToDashCase(rootProperty) + '-changed';
      dispatchNotifyEvent(inst, eventName, props[path], path);
      return true;
    }
    return false;
  }

  /**
   * Dispatches {property}-changed events to indicate a property (or path)
   * changed.
   *
   * @param {!PropertyEffectsType} inst The element from which to fire the event
   * @param {string} eventName The name of the event to send ('{property}-changed')
   * @param {*} value The value of the changed property
   * @param {string | null | undefined} path If a sub-path of this property changed, the path
   *   that changed (optional).
   * @private
   * @suppress {invalidCasts}
   */
  function dispatchNotifyEvent(inst, eventName, value, path) {
    let detail = {
      value: value,
      queueProperty: true
    };
    if (path) {
      detail.path = path;
    }
    /** @type {!HTMLElement} */(inst).dispatchEvent(new CustomEvent(eventName, { detail }));
  }

  /**
   * Implements the "notify" effect.
   *
   * Dispatches a non-bubbling event named `info.eventName` on the instance
   * with a detail object containing the new `value`.
   *
   * @param {!PropertyEffectsType} inst The instance the effect will be run on
   * @param {string} property Name of property
   * @param {Object} props Bag of current property changes
   * @param {Object} oldProps Bag of previous values for changed properties
   * @param {?} info Effect metadata
   * @param {boolean} hasPaths True with `props` contains one or more paths
   * @private
   */
  function runNotifyEffect(inst, property, props, oldProps, info, hasPaths) {
    let rootProperty = hasPaths ? Polymer.Path.root(property) : property;
    let path = rootProperty != property ? property : null;
    let value = path ? Polymer.Path.get(inst, path) : inst.__data[property];
    if (path && value === undefined) {
      value = props[property];  // specifically for .splices
    }
    dispatchNotifyEvent(inst, info.eventName, value, path);
  }

  /**
   * Handler function for 2-way notification events. Receives context
   * information captured in the `addNotifyListener` closure from the
   * `__notifyListeners` metadata.
   *
   * Sets the value of the notified property to the host property or path.  If
   * the event contained path information, translate that path to the host
   * scope's name for that path first.
   *
   * @param {CustomEvent} event Notification event (e.g. '<property>-changed')
   * @param {!PropertyEffectsType} inst Host element instance handling the notification event
   * @param {string} fromProp Child element property that was bound
   * @param {string} toPath Host property/path that was bound
   * @param {boolean} negate Whether the binding was negated
   * @private
   */
  function handleNotification(event, inst, fromProp, toPath, negate) {
    let value;
    let detail = /** @type {Object} */(event.detail);
    let fromPath = detail && detail.path;
    if (fromPath) {
      toPath = Polymer.Path.translate(fromProp, toPath, fromPath);
      value = detail && detail.value;
    } else {
      value = event.target[fromProp];
    }
    value = negate ? !value : value;
    if (!inst[TYPES.READ_ONLY] || !inst[TYPES.READ_ONLY][toPath]) {
      if (inst._setPendingPropertyOrPath(toPath, value, true, Boolean(fromPath))
        && (!detail || !detail.queueProperty)) {
        inst._invalidateProperties();
      }
    }
  }

  /**
   * Implements the "reflect" effect.
   *
   * Sets the attribute named `info.attrName` to the given property value.
   *
   * @param {!PropertyEffectsType} inst The instance the effect will be run on
   * @param {string} property Name of property
   * @param {Object} props Bag of current property changes
   * @param {Object} oldProps Bag of previous values for changed properties
   * @param {?} info Effect metadata
   * @private
   */
  function runReflectEffect(inst, property, props, oldProps, info) {
    let value = inst.__data[property];
    if (Polymer.sanitizeDOMValue) {
      value = Polymer.sanitizeDOMValue(value, info.attrName, 'attribute', /** @type {Node} */(inst));
    }
    inst._propertyToAttribute(property, info.attrName, value);
  }

  /**
   * Runs "computed" effects for a set of changed properties.
   *
   * This method differs from the generic `runEffects` method in that it
   * continues to run computed effects based on the output of each pass until
   * there are no more newly computed properties.  This ensures that all
   * properties that will be computed by the initial set of changes are
   * computed before other effects (binding propagation, observers, and notify)
   * run.
   *
   * @param {!PropertyEffectsType} inst The instance the effect will be run on
   * @param {!Object} changedProps Bag of changed properties
   * @param {!Object} oldProps Bag of previous values for changed properties
   * @param {boolean} hasPaths True with `props` contains one or more paths
   * @private
   */
  function runComputedEffects(inst, changedProps, oldProps, hasPaths) {
    let computeEffects = inst[TYPES.COMPUTE];
    if (computeEffects) {
      let inputProps = changedProps;
      while (runEffects(inst, computeEffects, inputProps, oldProps, hasPaths)) {
        Object.assign(oldProps, inst.__dataOld);
        Object.assign(changedProps, inst.__dataPending);
        inputProps = inst.__dataPending;
        inst.__dataPending = null;
      }
    }
  }

  /**
   * Implements the "computed property" effect by running the method with the
   * values of the arguments specified in the `info` object and setting the
   * return value to the computed property specified.
   *
   * @param {!PropertyEffectsType} inst The instance the effect will be run on
   * @param {string} property Name of property
   * @param {Object} props Bag of current property changes
   * @param {Object} oldProps Bag of previous values for changed properties
   * @param {?} info Effect metadata
   * @private
   */
  function runComputedEffect(inst, property, props, oldProps, info) {
    let result = runMethodEffect(inst, property, props, oldProps, info);
    let computedProp = info.methodInfo;
    if (inst.__dataHasAccessor && inst.__dataHasAccessor[computedProp]) {
      inst._setPendingProperty(computedProp, result, true);
    } else {
      inst[computedProp] = result;
    }
  }

  /**
   * Computes path changes based on path links set up using the `linkPaths`
   * API.
   *
   * @param {!PropertyEffectsType} inst The instance whose props are changing
   * @param {string | !Array<(string|number)>} path Path that has changed
   * @param {*} value Value of changed path
   * @private
   */
  function computeLinkedPaths(inst, path, value) {
    let links = inst.__dataLinkedPaths;
    if (links) {
      let link;
      for (let a in links) {
        let b = links[a];
        if (Polymer.Path.isDescendant(a, path)) {
          link = Polymer.Path.translate(a, b, path);
          inst._setPendingPropertyOrPath(link, value, true, true);
        } else if (Polymer.Path.isDescendant(b, path)) {
          link = Polymer.Path.translate(b, a, path);
          inst._setPendingPropertyOrPath(link, value, true, true);
        }
      }
    }
  }

  // -- bindings ----------------------------------------------

  /**
   * Adds binding metadata to the current `nodeInfo`, and binding effects
   * for all part dependencies to `templateInfo`.
   *
   * @param {Function} constructor Class that `_parseTemplate` is currently
   *   running on
   * @param {TemplateInfo} templateInfo Template metadata for current template
   * @param {NodeInfo} nodeInfo Node metadata for current template node
   * @param {string} kind Binding kind, either 'property', 'attribute', or 'text'
   * @param {string} target Target property name
   * @param {!Array<!BindingPart>} parts Array of binding part metadata
   * @param {string=} literal Literal text surrounding binding parts (specified
   *   only for 'property' bindings, since these must be initialized as part
   *   of boot-up)
   * @private
   */
  function addBinding(constructor, templateInfo, nodeInfo, kind, target, parts, literal) {
    // Create binding metadata and add to nodeInfo
    nodeInfo.bindings = nodeInfo.bindings || [];
    let /** Binding */ binding = { kind, target, parts, literal, isCompound: (parts.length !== 1) };
    nodeInfo.bindings.push(binding);
    // Add listener info to binding metadata
    if (shouldAddListener(binding)) {
      let {event, negate} = binding.parts[0];
      binding.listenerEvent = event || (CaseMap.camelToDashCase(target) + '-changed');
      binding.listenerNegate = negate;
    }
    // Add "propagate" property effects to templateInfo
    let index = templateInfo.nodeInfoList.length;
    for (let i=0; i<binding.parts.length; i++) {
      let part = binding.parts[i];
      part.compoundIndex = i;
      addEffectForBindingPart(constructor, templateInfo, binding, part, index);
    }
  }

  /**
   * Adds property effects to the given `templateInfo` for the given binding
   * part.
   *
   * @param {Function} constructor Class that `_parseTemplate` is currently
   *   running on
   * @param {TemplateInfo} templateInfo Template metadata for current template
   * @param {!Binding} binding Binding metadata
   * @param {!BindingPart} part Binding part metadata
   * @param {number} index Index into `nodeInfoList` for this node
   */
  function addEffectForBindingPart(constructor, templateInfo, binding, part, index) {
    if (!part.literal) {
      if (binding.kind === 'attribute' && binding.target[0] === '-') {
        console.warn('Cannot set attribute ' + binding.target +
          ' because "-" is not a valid attribute starting character');
      } else {
        let dependencies = part.dependencies;
        let info = { index, binding, part, evaluator: constructor };
        for (let j=0; j<dependencies.length; j++) {
          let trigger = dependencies[j];
          if (typeof trigger == 'string') {
            trigger = parseArg(trigger);
            trigger.wildcard = true;
          }
          constructor._addTemplatePropertyEffect(templateInfo, trigger.rootProperty, {
            fn: runBindingEffect,
            info, trigger
          });
        }
      }
    }
  }

  /**
   * Implements the "binding" (property/path binding) effect.
   *
   * Note that binding syntax is overridable via `_parseBindings` and
   * `_evaluateBinding`.  This method will call `_evaluateBinding` for any
   * non-literal parts returned from `_parseBindings`.  However,
   * there is no support for _path_ bindings via custom binding parts,
   * as this is specific to Polymer's path binding syntax.
   *
   * @param {!PropertyEffectsType} inst The instance the effect will be run on
   * @param {string} path Name of property
   * @param {Object} props Bag of current property changes
   * @param {Object} oldProps Bag of previous values for changed properties
   * @param {?} info Effect metadata
   * @param {boolean} hasPaths True with `props` contains one or more paths
   * @param {Array} nodeList List of nodes associated with `nodeInfoList` template
   *   metadata
   * @private
   */
  function runBindingEffect(inst, path, props, oldProps, info, hasPaths, nodeList) {
    let node = nodeList[info.index];
    let binding = info.binding;
    let part = info.part;
    // Subpath notification: transform path and set to client
    // e.g.: foo="{{obj.sub}}", path: 'obj.sub.prop', set 'foo.prop'=obj.sub.prop
    if (hasPaths && part.source && (path.length > part.source.length) &&
        (binding.kind == 'property') && !binding.isCompound &&
        node.__dataHasAccessor && node.__dataHasAccessor[binding.target]) {
      let value = props[path];
      path = Polymer.Path.translate(part.source, binding.target, path);
      if (node._setPendingPropertyOrPath(path, value, false, true)) {
        inst._enqueueClient(node);
      }
    } else {
      let value = info.evaluator._evaluateBinding(inst, part, path, props, oldProps, hasPaths);
      // Propagate value to child
      applyBindingValue(inst, node, binding, part, value);
    }
  }

  /**
   * Sets the value for an "binding" (binding) effect to a node,
   * either as a property or attribute.
   *
   * @param {!PropertyEffectsType} inst The instance owning the binding effect
   * @param {Node} node Target node for binding
   * @param {!Binding} binding Binding metadata
   * @param {!BindingPart} part Binding part metadata
   * @param {*} value Value to set
   * @private
   */
  function applyBindingValue(inst, node, binding, part, value) {
    value = computeBindingValue(node, value, binding, part);
    if (Polymer.sanitizeDOMValue) {
      value = Polymer.sanitizeDOMValue(value, binding.target, binding.kind, node);
    }
    if (binding.kind == 'attribute') {
      // Attribute binding
      inst._valueToNodeAttribute(/** @type {Element} */(node), value, binding.target);
    } else {
      // Property binding
      let prop = binding.target;
      if (node.__dataHasAccessor && node.__dataHasAccessor[prop]) {
        if (!node[TYPES.READ_ONLY] || !node[TYPES.READ_ONLY][prop]) {
          if (node._setPendingProperty(prop, value)) {
            inst._enqueueClient(node);
          }
        }
      } else  {
        inst._setUnmanagedPropertyToNode(node, prop, value);
      }
    }
  }

  /**
   * Transforms an "binding" effect value based on compound & negation
   * effect metadata, as well as handling for special-case properties
   *
   * @param {Node} node Node the value will be set to
   * @param {*} value Value to set
   * @param {!Binding} binding Binding metadata
   * @param {!BindingPart} part Binding part metadata
   * @return {*} Transformed value to set
   * @private
   */
  function computeBindingValue(node, value, binding, part) {
    if (binding.isCompound) {
      let storage = node.__dataCompoundStorage[binding.target];
      storage[part.compoundIndex] = value;
      value = storage.join('');
    }
    if (binding.kind !== 'attribute') {
      // Some browsers serialize `undefined` to `"undefined"`
      if (binding.target === 'textContent' ||
          (node.localName == 'input' && binding.target == 'value')) {
        value = value == undefined ? '' : value;
      }
    }
    return value;
  }

  /**
   * Returns true if a binding's metadata meets all the requirements to allow
   * 2-way binding, and therefore a `<property>-changed` event listener should be
   * added:
   * - used curly braces
   * - is a property (not attribute) binding
   * - is not a textContent binding
   * - is not compound
   *
   * @param {!Binding} binding Binding metadata
   * @return {boolean} True if 2-way listener should be added
   * @private
   */
  function shouldAddListener(binding) {
    return Boolean(binding.target) &&
           binding.kind != 'attribute' &&
           binding.kind != 'text' &&
           !binding.isCompound &&
           binding.parts[0].mode === '{';
  }

  /**
   * Setup compound binding storage structures, notify listeners, and dataHost
   * references onto the bound nodeList.
   *
   * @param {!PropertyEffectsType} inst Instance that bas been previously bound
   * @param {TemplateInfo} templateInfo Template metadata
   * @private
   */
  function setupBindings(inst, templateInfo) {
    // Setup compound storage, dataHost, and notify listeners
    let {nodeList, nodeInfoList} = templateInfo;
    if (nodeInfoList.length) {
      for (let i=0; i < nodeInfoList.length; i++) {
        let info = nodeInfoList[i];
        let node = nodeList[i];
        let bindings = info.bindings;
        if (bindings) {
          for (let i=0; i<bindings.length; i++) {
            let binding = bindings[i];
            setupCompoundStorage(node, binding);
            addNotifyListener(node, inst, binding);
          }
        }
        node.__dataHost = inst;
      }
    }
  }

  /**
   * Initializes `__dataCompoundStorage` local storage on a bound node with
   * initial literal data for compound bindings, and sets the joined
   * literal parts to the bound property.
   *
   * When changes to compound parts occur, they are first set into the compound
   * storage array for that property, and then the array is joined to result in
   * the final value set to the property/attribute.
   *
   * @param {Node} node Bound node to initialize
   * @param {Binding} binding Binding metadata
   * @private
   */
  function setupCompoundStorage(node, binding) {
    if (binding.isCompound) {
      // Create compound storage map
      let storage = node.__dataCompoundStorage ||
        (node.__dataCompoundStorage = {});
      let parts = binding.parts;
      // Copy literals from parts into storage for this binding
      let literals = new Array(parts.length);
      for (let j=0; j<parts.length; j++) {
        literals[j] = parts[j].literal;
      }
      let target = binding.target;
      storage[target] = literals;
      // Configure properties with their literal parts
      if (binding.literal && binding.kind == 'property') {
        node[target] = binding.literal;
      }
    }
  }

  /**
   * Adds a 2-way binding notification event listener to the node specified
   *
   * @param {Object} node Child element to add listener to
   * @param {!PropertyEffectsType} inst Host element instance to handle notification event
   * @param {Binding} binding Binding metadata
   * @private
   */
  function addNotifyListener(node, inst, binding) {
    if (binding.listenerEvent) {
      let part = binding.parts[0];
      node.addEventListener(binding.listenerEvent, function(e) {
        handleNotification(e, inst, binding.target, part.source, part.negate);
      });
    }
  }

  // -- for method-based effects (complexObserver & computed) --------------

  /**
   * Adds property effects for each argument in the method signature (and
   * optionally, for the method name if `dynamic` is true) that calls the
   * provided effect function.
   *
   * @param {Element | Object} model Prototype or instance
   * @param {!MethodSignature} sig Method signature metadata
   * @param {string} type Type of property effect to add
   * @param {Function} effectFn Function to run when arguments change
   * @param {*=} methodInfo Effect-specific information to be included in
   *   method effect metadata
   * @param {boolean|Object=} dynamicFn Boolean or object map indicating whether
   *   method names should be included as a dependency to the effect. Note,
   *   defaults to true if the signature is static (sig.static is true).
   * @private
   */
  function createMethodEffect(model, sig, type, effectFn, methodInfo, dynamicFn) {
    dynamicFn = sig.static || (dynamicFn &&
      (typeof dynamicFn !== 'object' || dynamicFn[sig.methodName]));
    let info = {
      methodName: sig.methodName,
      args: sig.args,
      methodInfo,
      dynamicFn
    };
    for (let i=0, arg; (i<sig.args.length) && (arg=sig.args[i]); i++) {
      if (!arg.literal) {
        model._addPropertyEffect(arg.rootProperty, type, {
          fn: effectFn, info: info, trigger: arg
        });
      }
    }
    if (dynamicFn) {
      model._addPropertyEffect(sig.methodName, type, {
        fn: effectFn, info: info
      });
    }
  }

  /**
   * Calls a method with arguments marshaled from properties on the instance
   * based on the method signature contained in the effect metadata.
   *
   * Multi-property observers, computed properties, and inline computing
   * functions call this function to invoke the method, then use the return
   * value accordingly.
   *
   * @param {!PropertyEffectsType} inst The instance the effect will be run on
   * @param {string} property Name of property
   * @param {Object} props Bag of current property changes
   * @param {Object} oldProps Bag of previous values for changed properties
   * @param {?} info Effect metadata
   * @return {*} Returns the return value from the method invocation
   * @private
   */
  function runMethodEffect(inst, property, props, oldProps, info) {
    // Instances can optionally have a _methodHost which allows redirecting where
    // to find methods. Currently used by `templatize`.
    let context = inst._methodHost || inst;
    let fn = context[info.methodName];
    if (fn) {
      let args = marshalArgs(inst.__data, info.args, property, props);
      return fn.apply(context, args);
    } else if (!info.dynamicFn) {
      console.warn('method `' + info.methodName + '` not defined');
    }
  }

  const emptyArray = [];

  // Regular expressions used for binding
  const IDENT  = '(?:' + '[a-zA-Z_$][\\w.:$\\-*]*' + ')';
  const NUMBER = '(?:' + '[-+]?[0-9]*\\.?[0-9]+(?:[eE][-+]?[0-9]+)?' + ')';
  const SQUOTE_STRING = '(?:' + '\'(?:[^\'\\\\]|\\\\.)*\'' + ')';
  const DQUOTE_STRING = '(?:' + '"(?:[^"\\\\]|\\\\.)*"' + ')';
  const STRING = '(?:' + SQUOTE_STRING + '|' + DQUOTE_STRING + ')';
  const ARGUMENT = '(?:(' + IDENT + '|' + NUMBER + '|' +  STRING + ')\\s*' + ')';
  const ARGUMENTS = '(?:' + ARGUMENT + '(?:,\\s*' + ARGUMENT + ')*' + ')';
  const ARGUMENT_LIST = '(?:' + '\\(\\s*' +
                                '(?:' + ARGUMENTS + '?' + ')' +
                              '\\)\\s*' + ')';
  const BINDING = '(' + IDENT + '\\s*' + ARGUMENT_LIST + '?' + ')'; // Group 3
  const OPEN_BRACKET = '(\\[\\[|{{)' + '\\s*';
  const CLOSE_BRACKET = '(?:]]|}})';
  const NEGATE = '(?:(!)\\s*)?'; // Group 2
  const EXPRESSION = OPEN_BRACKET + NEGATE + BINDING + CLOSE_BRACKET;
  const bindingRegex = new RegExp(EXPRESSION, "g");

  /**
   * Create a string from binding parts of all the literal parts
   *
   * @param {!Array<BindingPart>} parts All parts to stringify
   * @return {string} String made from the literal parts
   */
  function literalFromParts(parts) {
    let s = '';
    for (let i=0; i<parts.length; i++) {
      let literal = parts[i].literal;
      s += literal || '';
    }
    return s;
  }

  /**
   * Parses an expression string for a method signature, and returns a metadata
   * describing the method in terms of `methodName`, `static` (whether all the
   * arguments are literals), and an array of `args`
   *
   * @param {string} expression The expression to parse
   * @return {?MethodSignature} The method metadata object if a method expression was
   *   found, otherwise `undefined`
   * @private
   */
  function parseMethod(expression) {
    // tries to match valid javascript property names
    let m = expression.match(/([^\s]+?)\(([\s\S]*)\)/);
    if (m) {
      let methodName = m[1];
      let sig = { methodName, static: true, args: emptyArray };
      if (m[2].trim()) {
        // replace escaped commas with comma entity, split on un-escaped commas
        let args = m[2].replace(/\\,/g, '&comma;').split(',');
        return parseArgs(args, sig);
      } else {
        return sig;
      }
    }
    return null;
  }

  /**
   * Parses an array of arguments and sets the `args` property of the supplied
   * signature metadata object. Sets the `static` property to false if any
   * argument is a non-literal.
   *
   * @param {!Array<string>} argList Array of argument names
   * @param {!MethodSignature} sig Method signature metadata object
   * @return {!MethodSignature} The updated signature metadata object
   * @private
   */
  function parseArgs(argList, sig) {
    sig.args = argList.map(function(rawArg) {
      let arg = parseArg(rawArg);
      if (!arg.literal) {
        sig.static = false;
      }
      return arg;
    }, this);
    return sig;
  }

  /**
   * Parses an individual argument, and returns an argument metadata object
   * with the following fields:
   *
   *   {
   *     value: 'prop',        // property/path or literal value
   *     literal: false,       // whether argument is a literal
   *     structured: false,    // whether the property is a path
   *     rootProperty: 'prop', // the root property of the path
   *     wildcard: false       // whether the argument was a wildcard '.*' path
   *   }
   *
   * @param {string} rawArg The string value of the argument
   * @return {!MethodArg} Argument metadata object
   * @private
   */
  function parseArg(rawArg) {
    // clean up whitespace
    let arg = rawArg.trim()
      // replace comma entity with comma
      .replace(/&comma;/g, ',')
      // repair extra escape sequences; note only commas strictly need
      // escaping, but we allow any other char to be escaped since its
      // likely users will do this
      .replace(/\\(.)/g, '\$1')
      ;
    // basic argument descriptor
    let a = {
      name: arg,
      value: '',
      literal: false
    };
    // detect literal value (must be String or Number)
    let fc = arg[0];
    if (fc === '-') {
      fc = arg[1];
    }
    if (fc >= '0' && fc <= '9') {
      fc = '#';
    }
    switch(fc) {
      case "'":
      case '"':
        a.value = arg.slice(1, -1);
        a.literal = true;
        break;
      case '#':
        a.value = Number(arg);
        a.literal = true;
        break;
    }
    // if not literal, look for structured path
    if (!a.literal) {
      a.rootProperty = Polymer.Path.root(arg);
      // detect structured path (has dots)
      a.structured = Polymer.Path.isPath(arg);
      if (a.structured) {
        a.wildcard = (arg.slice(-2) == '.*');
        if (a.wildcard) {
          a.name = arg.slice(0, -2);
        }
      }
    }
    return a;
  }

  /**
   * Gather the argument values for a method specified in the provided array
   * of argument metadata.
   *
   * The `path` and `value` arguments are used to fill in wildcard descriptor
   * when the method is being called as a result of a path notification.
   *
   * @param {Object} data Instance data storage object to read properties from
   * @param {!Array<!MethodArg>} args Array of argument metadata
   * @param {string} path Property/path name that triggered the method effect
   * @param {Object} props Bag of current property changes
   * @return {Array<*>} Array of argument values
   * @private
   */
  function marshalArgs(data, args, path, props) {
    let values = [];
    for (let i=0, l=args.length; i<l; i++) {
      let arg = args[i];
      let name = arg.name;
      let v;
      if (arg.literal) {
        v = arg.value;
      } else {
        if (arg.structured) {
          v = Polymer.Path.get(data, name);
          // when data is not stored e.g. `splices`
          if (v === undefined) {
            v = props[name];
          }
        } else {
          v = data[name];
        }
      }
      if (arg.wildcard) {
        // Only send the actual path changed info if the change that
        // caused the observer to run matched the wildcard
        let baseChanged = (name.indexOf(path + '.') === 0);
        let matches = (path.indexOf(name) === 0 && !baseChanged);
        values[i] = {
          path: matches ? path : name,
          value: matches ? props[path] : v,
          base: v
        };
      } else {
        values[i] = v;
      }
    }
    return values;
  }

  // data api

  /**
   * Sends array splice notifications (`.splices` and `.length`)
   *
   * Note: this implementation only accepts normalized paths
   *
   * @param {!PropertyEffectsType} inst Instance to send notifications to
   * @param {Array} array The array the mutations occurred on
   * @param {string} path The path to the array that was mutated
   * @param {Array} splices Array of splice records
   * @private
   */
  function notifySplices(inst, array, path, splices) {
    let splicesPath = path + '.splices';
    inst.notifyPath(splicesPath, { indexSplices: splices });
    inst.notifyPath(path + '.length', array.length);
    // Null here to allow potentially large splice records to be GC'ed.
    inst.__data[splicesPath] = {indexSplices: null};
  }

  /**
   * Creates a splice record and sends an array splice notification for
   * the described mutation
   *
   * Note: this implementation only accepts normalized paths
   *
   * @param {!PropertyEffectsType} inst Instance to send notifications to
   * @param {Array} array The array the mutations occurred on
   * @param {string} path The path to the array that was mutated
   * @param {number} index Index at which the array mutation occurred
   * @param {number} addedCount Number of added items
   * @param {Array} removed Array of removed items
   * @private
   */
  function notifySplice(inst, array, path, index, addedCount, removed) {
    notifySplices(inst, array, path, [{
      index: index,
      addedCount: addedCount,
      removed: removed,
      object: array,
      type: 'splice'
    }]);
  }

  /**
   * Returns an upper-cased version of the string.
   *
   * @param {string} name String to uppercase
   * @return {string} Uppercased string
   * @private
   */
  function upper(name) {
    return name[0].toUpperCase() + name.substring(1);
  }

  /**
   * Element class mixin that provides meta-programming for Polymer's template
   * binding and data observation (collectively, "property effects") system.
   *
   * This mixin uses provides the following key static methods for adding
   * property effects to an element class:
   * - `addPropertyEffect`
   * - `createPropertyObserver`
   * - `createMethodObserver`
   * - `createNotifyingProperty`
   * - `createReadOnlyProperty`
   * - `createReflectedProperty`
   * - `createComputedProperty`
   * - `bindTemplate`
   *
   * Each method creates one or more property accessors, along with metadata
   * used by this mixin's implementation of `_propertiesChanged` to perform
   * the property effects.
   *
   * Underscored versions of the above methods also exist on the element
   * prototype for adding property effects on instances at runtime.
   *
   * Note that this mixin overrides several `PropertyAccessors` methods, in
   * many cases to maintain guarantees provided by the Polymer 1.x features;
   * notably it changes property accessors to be synchronous by default
   * whereas the default when using `PropertyAccessors` standalone is to be
   * async by default.
   *
   * @mixinFunction
   * @polymer
   * @appliesMixin Polymer.TemplateStamp
   * @appliesMixin Polymer.PropertyAccessors
   * @memberof Polymer
   * @summary Element class mixin that provides meta-programming for Polymer's
   * template binding and data observation system.
   */
  Polymer.PropertyEffects = Polymer.dedupingMixin(superClass => {

    /**
     * @constructor
     * @extends {superClass}
     * @implements {Polymer_PropertyAccessors}
     * @implements {Polymer_TemplateStamp}
     * @unrestricted
     */
    const propertyEffectsBase = Polymer.TemplateStamp(Polymer.PropertyAccessors(superClass));

    /**
     * @polymer
     * @mixinClass
     * @implements {Polymer_PropertyEffects}
     * @extends {propertyEffectsBase}
     * @unrestricted
     */
    class PropertyEffects extends propertyEffectsBase {

      constructor() {
        super();
        /** @type {boolean} */
        this.__dataClientsReady;
        /** @type {Array} */
        this.__dataPendingClients;
        /** @type {Object} */
        this.__dataToNotify;
        /** @type {Object} */
        this.__dataLinkedPaths;
        /** @type {boolean} */
        this.__dataHasPaths;
        /** @type {Object} */
        this.__dataCompoundStorage;
        /** @type {Polymer_PropertyEffects} */
        this.__dataHost;
        /** @type {!Object} */
        this.__dataTemp;
        /** @type {boolean} */
        this.__dataClientsInitialized;
        /** @type {!Object} */
        this.__data;
        /** @type {!Object} */
        this.__dataPending;
        /** @type {!Object} */
        this.__dataOld;
        /** @type {Object} */
        this.__computeEffects;
        /** @type {Object} */
        this.__reflectEffects;
        /** @type {Object} */
        this.__notifyEffects;
        /** @type {Object} */
        this.__propagateEffects;
        /** @type {Object} */
        this.__observeEffects;
        /** @type {Object} */
        this.__readOnly;
        /** @type {number} */
        this.__dataCounter;
        /** @type {!TemplateInfo} */
        this.__templateInfo;
      }

      get PROPERTY_EFFECT_TYPES() {
        return TYPES;
      }

      _initializeProperties() {
        super._initializeProperties();
        hostStack.registerHost(this);
        this.__dataClientsReady = false;
        this.__dataPendingClients = null;
        this.__dataToNotify = null;
        this.__dataLinkedPaths = null;
        this.__dataHasPaths = false;
        // May be set on instance prior to upgrade
        this.__dataCompoundStorage = this.__dataCompoundStorage || null;
        this.__dataHost = this.__dataHost || null;
        this.__dataTemp = {};
        this.__dataClientsInitialized = false;
      }

      /**
       * Overrides `Polymer.PropertyAccessors` implementation to provide a
       * more efficient implementation of initializing properties from
       * the prototype on the instance.
       *
       * @override
       * @param {Object} props Properties to initialize on the prototype
       */
      _initializeProtoProperties(props) {
        this.__data = Object.create(props);
        this.__dataPending = Object.create(props);
        this.__dataOld = {};
      }

      /**
       * Overrides `Polymer.PropertyAccessors` implementation to avoid setting
       * `_setProperty`'s `shouldNotify: true`.
       *
       * @override
       * @param {Object} props Properties to initialize on the instance
       */
      _initializeInstanceProperties(props) {
        let readOnly = this[TYPES.READ_ONLY];
        for (let prop in props) {
          if (!readOnly || !readOnly[prop]) {
            this.__dataPending = this.__dataPending || {};
            this.__dataOld = this.__dataOld || {};
            this.__data[prop] = this.__dataPending[prop] = props[prop];
          }
        }
      }

      // Prototype setup ----------------------------------------

      /**
       * Equivalent to static `addPropertyEffect` API but can be called on
       * an instance to add effects at runtime.  See that method for
       * full API docs.
       *
       * @param {string} property Property that should trigger the effect
       * @param {string} type Effect type, from this.PROPERTY_EFFECT_TYPES
       * @param {Object=} effect Effect metadata object
       * @protected
       */
      _addPropertyEffect(property, type, effect) {
        this._createPropertyAccessor(property, type == TYPES.READ_ONLY);
        // effects are accumulated into arrays per property based on type
        let effects = ensureOwnEffectMap(this, type)[property];
        if (!effects) {
          effects = this[type][property] = [];
        }
        effects.push(effect);
      }

      /**
       * Removes the given property effect.
       *
       * @param {string} property Property the effect was associated with
       * @param {string} type Effect type, from this.PROPERTY_EFFECT_TYPES
       * @param {Object=} effect Effect metadata object to remove
       */
      _removePropertyEffect(property, type, effect) {
        let effects = ensureOwnEffectMap(this, type)[property];
        let idx = effects.indexOf(effect);
        if (idx >= 0) {
          effects.splice(idx, 1);
        }
      }

      /**
       * Returns whether the current prototype/instance has a property effect
       * of a certain type.
       *
       * @param {string} property Property name
       * @param {string=} type Effect type, from this.PROPERTY_EFFECT_TYPES
       * @return {boolean} True if the prototype/instance has an effect of this type
       * @protected
       */
      _hasPropertyEffect(property, type) {
        let effects = this[type];
        return Boolean(effects && effects[property]);
      }

      /**
       * Returns whether the current prototype/instance has a "read only"
       * accessor for the given property.
       *
       * @param {string} property Property name
       * @return {boolean} True if the prototype/instance has an effect of this type
       * @protected
       */
      _hasReadOnlyEffect(property) {
        return this._hasPropertyEffect(property, TYPES.READ_ONLY);
      }

      /**
       * Returns whether the current prototype/instance has a "notify"
       * property effect for the given property.
       *
       * @param {string} property Property name
       * @return {boolean} True if the prototype/instance has an effect of this type
       * @protected
       */
      _hasNotifyEffect(property) {
        return this._hasPropertyEffect(property, TYPES.NOTIFY);
      }

      /**
       * Returns whether the current prototype/instance has a "reflect to attribute"
       * property effect for the given property.
       *
       * @param {string} property Property name
       * @return {boolean} True if the prototype/instance has an effect of this type
       * @protected
       */
      _hasReflectEffect(property) {
        return this._hasPropertyEffect(property, TYPES.REFLECT);
      }

      /**
       * Returns whether the current prototype/instance has a "computed"
       * property effect for the given property.
       *
       * @param {string} property Property name
       * @return {boolean} True if the prototype/instance has an effect of this type
       * @protected
       */
      _hasComputedEffect(property) {
        return this._hasPropertyEffect(property, TYPES.COMPUTE);
      }

      // Runtime ----------------------------------------

      /**
       * Sets a pending property or path.  If the root property of the path in
       * question had no accessor, the path is set, otherwise it is enqueued
       * via `_setPendingProperty`.
       *
       * This function isolates relatively expensive functionality necessary
       * for the public API (`set`, `setProperties`, `notifyPath`, and property
       * change listeners via {{...}} bindings), such that it is only done
       * when paths enter the system, and not at every propagation step.  It
       * also sets a `__dataHasPaths` flag on the instance which is used to
       * fast-path slower path-matching code in the property effects host paths.
       *
       * `path` can be a path string or array of path parts as accepted by the
       * public API.
       *
       * @param {string | !Array<number|string>} path Path to set
       * @param {*} value Value to set
       * @param {boolean=} shouldNotify Set to true if this change should
       *  cause a property notification event dispatch
       * @param {boolean=} isPathNotification If the path being set is a path
       *   notification of an already changed value, as opposed to a request
       *   to set and notify the change.  In the latter `false` case, a dirty
       *   check is performed and then the value is set to the path before
       *   enqueuing the pending property change.
       * @return {boolean} Returns true if the property/path was enqueued in
       *   the pending changes bag.
       * @protected
       */
      _setPendingPropertyOrPath(path, value, shouldNotify, isPathNotification) {
        if (isPathNotification ||
            Polymer.Path.root(Array.isArray(path) ? path[0] : path) !== path) {
          // Dirty check changes being set to a path against the actual object,
          // since this is the entry point for paths into the system; from here
          // the only dirty checks are against the `__dataTemp` cache to prevent
          // duplicate work in the same turn only. Note, if this was a notification
          // of a change already set to a path (isPathNotification: true),
          // we always let the change through and skip the `set` since it was
          // already dirty checked at the point of entry and the underlying
          // object has already been updated
          if (!isPathNotification) {
            let old = Polymer.Path.get(this, path);
            path = /** @type {string} */ (Polymer.Path.set(this, path, value));
            // Use property-accessor's simpler dirty check
            if (!path || !super._shouldPropertyChange(path, value, old)) {
              return false;
            }
          }
          this.__dataHasPaths = true;
          if (this._setPendingProperty(/**@type{string}*/(path), value, shouldNotify)) {
            computeLinkedPaths(this, path, value);
            return true;
          }
        } else {
          if (this.__dataHasAccessor && this.__dataHasAccessor[path]) {
            return this._setPendingProperty(/**@type{string}*/(path), value, shouldNotify);
          } else {
            this[path] = value;
          }
        }
        return false;
      }

      /**
       * Applies a value to a non-Polymer element/node's property.
       *
       * The implementation makes a best-effort at binding interop:
       * Some native element properties have side-effects when
       * re-setting the same value (e.g. setting `<input>.value` resets the
       * cursor position), so we do a dirty-check before setting the value.
       * However, for better interop with non-Polymer custom elements that
       * accept objects, we explicitly re-set object changes coming from the
       * Polymer world (which may include deep object changes without the
       * top reference changing), erring on the side of providing more
       * information.
       *
       * Users may override this method to provide alternate approaches.
       *
       * @param {Node} node The node to set a property on
       * @param {string} prop The property to set
       * @param {*} value The value to set
       * @protected
       */
      _setUnmanagedPropertyToNode(node, prop, value) {
        // It is a judgment call that resetting primitives is
        // "bad" and resettings objects is also "good"; alternatively we could
        // implement a whitelist of tag & property values that should never
        // be reset (e.g. <input>.value && <select>.value)
        if (value !== node[prop] || typeof value == 'object') {
          node[prop] = value;
        }
      }

      /**
       * Overrides the `PropertyAccessors` implementation to introduce special
       * dirty check logic depending on the property & value being set:
       *
       * 1. Any value set to a path (e.g. 'obj.prop': 42 or 'obj.prop': {...})
       *    Stored in `__dataTemp`, dirty checked against `__dataTemp`
       * 2. Object set to simple property (e.g. 'prop': {...})
       *    Stored in `__dataTemp` and `__data`, dirty checked against
       *    `__dataTemp` by default implementation of `_shouldPropertyChange`
       * 3. Primitive value set to simple property (e.g. 'prop': 42)
       *    Stored in `__data`, dirty checked against `__data`
       *
       * The dirty-check is important to prevent cycles due to two-way
       * notification, but paths and objects are only dirty checked against any
       * previous value set during this turn via a "temporary cache" that is
       * cleared when the last `_propertiesChaged` exits. This is so:
       * a. any cached array paths (e.g. 'array.3.prop') may be invalidated
       *    due to array mutations like shift/unshift/splice; this is fine
       *    since path changes are dirty-checked at user entry points like `set`
       * b. dirty-checking for objects only lasts one turn to allow the user
       *    to mutate the object in-place and re-set it with the same identity
       *    and have all sub-properties re-propagated in a subsequent turn.
       *
       * The temp cache is not necessarily sufficient to prevent invalid array
       * paths, since a splice can happen during the same turn (with pathological
       * user code); we could introduce a "fixup" for temporarily cached array
       * paths if needed: https://github.com/Polymer/polymer/issues/4227
       *
       * @param {string} property Name of the property
       * @param {*} value Value to set
       * @param {boolean=} shouldNotify True if property should fire notification
       *   event (applies only for `notify: true` properties)
       * @return {boolean} Returns true if the property changed
       * @override
       */
      _setPendingProperty(property, value, shouldNotify) {
        let isPath = this.__dataHasPaths && Polymer.Path.isPath(property);
        let prevProps = isPath ? this.__dataTemp : this.__data;
        if (this._shouldPropertyChange(property, value, prevProps[property])) {
          if (!this.__dataPending) {
            this.__dataPending = {};
            this.__dataOld = {};
          }
          // Ensure old is captured from the last turn
          if (!(property in this.__dataOld)) {
            this.__dataOld[property] = this.__data[property];
          }
          // Paths are stored in temporary cache (cleared at end of turn),
          // which is used for dirty-checking, all others stored in __data
          if (isPath) {
            this.__dataTemp[property] = value;
          } else {
            this.__data[property] = value;
          }
          // All changes go into pending property bag, passed to _propertiesChanged
          this.__dataPending[property] = value;
          // Track properties that should notify separately
          if (isPath || (this[TYPES.NOTIFY] && this[TYPES.NOTIFY][property])) {
            this.__dataToNotify = this.__dataToNotify || {};
            this.__dataToNotify[property] = shouldNotify;
          }
          return true;
        }
        return false;
      }

      /**
       * Overrides base implementation to ensure all accessors set `shouldNotify`
       * to true, for per-property notification tracking.
       *
       * @override
       */
      _setProperty(property, value) {
        if (this._setPendingProperty(property, value, true)) {
          this._invalidateProperties();
        }
      }

      /**
       * Overrides `PropertyAccessor`'s default async queuing of
       * `_propertiesChanged`: if `__dataReady` is false (has not yet been
       * manually flushed), the function no-ops; otherwise flushes
       * `_propertiesChanged` synchronously.
       *
       * @override
       */
      _invalidateProperties() {
        if (this.__dataReady) {
          this._flushProperties();
        }
      }

      /**
       * Enqueues the given client on a list of pending clients, whose
       * pending property changes can later be flushed via a call to
       * `_flushClients`.
       *
       * @param {Object} client PropertyEffects client to enqueue
       * @protected
       */
      _enqueueClient(client) {
        this.__dataPendingClients = this.__dataPendingClients || [];
        if (client !== this) {
          this.__dataPendingClients.push(client);
        }
      }

      /**
       * Flushes any clients previously enqueued via `_enqueueClient`, causing
       * their `_flushProperties` method to run.
       *
       * @protected
       */
      _flushClients() {
        if (!this.__dataClientsReady) {
          this.__dataClientsReady = true;
          this._readyClients();
          // Override point where accessors are turned on; importantly,
          // this is after clients have fully readied, providing a guarantee
          // that any property effects occur only after all clients are ready.
          this.__dataReady = true;
        } else {
          this.__enableOrFlushClients();
        }
      }

      // NOTE: We ensure clients either enable or flush as appropriate. This
      // handles two corner cases:
      // (1) clients flush properly when connected/enabled before the host
      // enables; e.g.
      //   (a) Templatize stamps with no properties and does not flush and
      //   (b) the instance is inserted into dom and
      //   (c) then the instance flushes.
      // (2) clients enable properly when not connected/enabled when the host
      // flushes; e.g.
      //   (a) a template is runtime stamped and not yet connected/enabled
      //   (b) a host sets a property, causing stamped dom to flush
      //   (c) the stamped dom enables.
      __enableOrFlushClients() {
        let clients = this.__dataPendingClients;
        if (clients) {
          this.__dataPendingClients = null;
          for (let i=0; i < clients.length; i++) {
            let client = clients[i];
            if (!client.__dataEnabled) {
              client._enableProperties();
            } else if (client.__dataPending) {
              client._flushProperties();
            }
          }
        }
      }

      /**
       * Perform any initial setup on client dom. Called before the first
       * `_flushProperties` call on client dom and before any element
       * observers are called.
       *
       * @protected
       */
      _readyClients() {
        this.__enableOrFlushClients();
      }

      /**
       * Sets a bag of property changes to this instance, and
       * synchronously processes all effects of the properties as a batch.
       *
       * Property names must be simple properties, not paths.  Batched
       * path propagation is not supported.
       *
       * @param {Object} props Bag of one or more key-value pairs whose key is
       *   a property and value is the new value to set for that property.
       * @param {boolean=} setReadOnly When true, any private values set in
       *   `props` will be set. By default, `setProperties` will not set
       *   `readOnly: true` root properties.
       * @public
       */
      setProperties(props, setReadOnly) {
        for (let path in props) {
          if (setReadOnly || !this[TYPES.READ_ONLY] || !this[TYPES.READ_ONLY][path]) {
            //TODO(kschaaf): explicitly disallow paths in setProperty?
            // wildcard observers currently only pass the first changed path
            // in the `info` object, and you could do some odd things batching
            // paths, e.g. {'foo.bar': {...}, 'foo': null}
            this._setPendingPropertyOrPath(path, props[path], true);
          }
        }
        this._invalidateProperties();
      }

      /**
       * Overrides `PropertyAccessors` so that property accessor
       * side effects are not enabled until after client dom is fully ready.
       * Also calls `_flushClients` callback to ensure client dom is enabled
       * that was not enabled as a result of flushing properties.
       *
       * @override
       */
      ready() {
        // It is important that `super.ready()` is not called here as it
        // immediately turns on accessors. Instead, we wait until `readyClients`
        // to enable accessors to provide a guarantee that clients are ready
        // before processing any accessors side effects.
        this._flushProperties();
        // If no data was pending, `_flushProperties` will not `flushClients`
        // so ensure this is done.
        if (!this.__dataClientsReady) {
          this._flushClients();
        }
        // Before ready, client notifications do not trigger _flushProperties.
        // Therefore a flush is necessary here if data has been set.
        if (this.__dataPending) {
          this._flushProperties();
        }
      }

      /**
       * Implements `PropertyAccessors`'s properties changed callback.
       *
       * Runs each class of effects for the batch of changed properties in
       * a specific order (compute, propagate, reflect, observe, notify).
       *
       * @override
       */
      _propertiesChanged(currentProps, changedProps, oldProps) {
        // ----------------------------
        // let c = Object.getOwnPropertyNames(changedProps || {});
        // window.debug && console.group(this.localName + '#' + this.id + ': ' + c);
        // if (window.debug) { debugger; }
        // ----------------------------
        let hasPaths = this.__dataHasPaths;
        this.__dataHasPaths = false;
        // Compute properties
        runComputedEffects(this, changedProps, oldProps, hasPaths);
        // Clear notify properties prior to possible reentry (propagate, observe),
        // but after computing effects have a chance to add to them
        let notifyProps = this.__dataToNotify;
        this.__dataToNotify = null;
        // Propagate properties to clients
        this._propagatePropertyChanges(changedProps, oldProps, hasPaths);
        // Flush clients
        this._flushClients();
        // Reflect properties
        runEffects(this, this[TYPES.REFLECT], changedProps, oldProps, hasPaths);
        // Observe properties
        runEffects(this, this[TYPES.OBSERVE], changedProps, oldProps, hasPaths);
        // Notify properties to host
        if (notifyProps) {
          runNotifyEffects(this, notifyProps, changedProps, oldProps, hasPaths);
        }
        // Clear temporary cache at end of turn
        if (this.__dataCounter == 1) {
          this.__dataTemp = {};
        }
        // ----------------------------
        // window.debug && console.groupEnd(this.localName + '#' + this.id + ': ' + c);
        // ----------------------------
      }

      /**
       * Called to propagate any property changes to stamped template nodes
       * managed by this element.
       *
       * @param {Object} changedProps Bag of changed properties
       * @param {Object} oldProps Bag of previous values for changed properties
       * @param {boolean} hasPaths True with `props` contains one or more paths
       * @protected
       */
      _propagatePropertyChanges(changedProps, oldProps, hasPaths) {
        if (this[TYPES.PROPAGATE]) {
          runEffects(this, this[TYPES.PROPAGATE], changedProps, oldProps, hasPaths);
        }
        let templateInfo = this.__templateInfo;
        while (templateInfo) {
          runEffects(this, templateInfo.propertyEffects, changedProps, oldProps,
            hasPaths, templateInfo.nodeList);
          templateInfo = templateInfo.nextTemplateInfo;
        }
      }

      /**
       * Aliases one data path as another, such that path notifications from one
       * are routed to the other.
       *
       * @param {string | !Array<string|number>} to Target path to link.
       * @param {string | !Array<string|number>} from Source path to link.
       * @public
       */
      linkPaths(to, from) {
        to = Polymer.Path.normalize(to);
        from = Polymer.Path.normalize(from);
        this.__dataLinkedPaths = this.__dataLinkedPaths || {};
        this.__dataLinkedPaths[to] = from;
      }

      /**
       * Removes a data path alias previously established with `_linkPaths`.
       *
       * Note, the path to unlink should be the target (`to`) used when
       * linking the paths.
       *
       * @param {string | !Array<string|number>} path Target path to unlink.
       * @public
       */
      unlinkPaths(path) {
        path = Polymer.Path.normalize(path);
        if (this.__dataLinkedPaths) {
          delete this.__dataLinkedPaths[path];
        }
      }

      /**
       * Notify that an array has changed.
       *
       * Example:
       *
       *     this.items = [ {name: 'Jim'}, {name: 'Todd'}, {name: 'Bill'} ];
       *     ...
       *     this.items.splice(1, 1, {name: 'Sam'});
       *     this.items.push({name: 'Bob'});
       *     this.notifySplices('items', [
       *       { index: 1, removed: [{name: 'Todd'}], addedCount: 1, obect: this.items, type: 'splice' },
       *       { index: 3, removed: [], addedCount: 1, object: this.items, type: 'splice'}
       *     ]);
       *
       * @param {string} path Path that should be notified.
       * @param {Array} splices Array of splice records indicating ordered
       *   changes that occurred to the array. Each record should have the
       *   following fields:
       *    * index: index at which the change occurred
       *    * removed: array of items that were removed from this index
       *    * addedCount: number of new items added at this index
       *    * object: a reference to the array in question
       *    * type: the string literal 'splice'
       *
       *   Note that splice records _must_ be normalized such that they are
       *   reported in index order (raw results from `Object.observe` are not
       *   ordered and must be normalized/merged before notifying).
       * @public
      */
      notifySplices(path, splices) {
        let info = {path: ''};
        let array = /** @type {Array} */(Polymer.Path.get(this, path, info));
        notifySplices(this, array, info.path, splices);
      }

      /**
       * Convenience method for reading a value from a path.
       *
       * Note, if any part in the path is undefined, this method returns
       * `undefined` (this method does not throw when dereferencing undefined
       * paths).
       *
       * @param {(string|!Array<(string|number)>)} path Path to the value
       *   to read.  The path may be specified as a string (e.g. `foo.bar.baz`)
       *   or an array of path parts (e.g. `['foo.bar', 'baz']`).  Note that
       *   bracketed expressions are not supported; string-based path parts
       *   *must* be separated by dots.  Note that when dereferencing array
       *   indices, the index may be used as a dotted part directly
       *   (e.g. `users.12.name` or `['users', 12, 'name']`).
       * @param {Object=} root Root object from which the path is evaluated.
       * @return {*} Value at the path, or `undefined` if any part of the path
       *   is undefined.
       * @public
       */
      get(path, root) {
        return Polymer.Path.get(root || this, path);
      }

      /**
       * Convenience method for setting a value to a path and notifying any
       * elements bound to the same path.
       *
       * Note, if any part in the path except for the last is undefined,
       * this method does nothing (this method does not throw when
       * dereferencing undefined paths).
       *
       * @param {(string|!Array<(string|number)>)} path Path to the value
       *   to write.  The path may be specified as a string (e.g. `'foo.bar.baz'`)
       *   or an array of path parts (e.g. `['foo.bar', 'baz']`).  Note that
       *   bracketed expressions are not supported; string-based path parts
       *   *must* be separated by dots.  Note that when dereferencing array
       *   indices, the index may be used as a dotted part directly
       *   (e.g. `'users.12.name'` or `['users', 12, 'name']`).
       * @param {*} value Value to set at the specified path.
       * @param {Object=} root Root object from which the path is evaluated.
       *   When specified, no notification will occur.
       * @public
      */
      set(path, value, root) {
        if (root) {
          Polymer.Path.set(root, path, value);
        } else {
          if (!this[TYPES.READ_ONLY] || !this[TYPES.READ_ONLY][/** @type {string} */(path)]) {
            if (this._setPendingPropertyOrPath(path, value, true)) {
              this._invalidateProperties();
            }
          }
        }
      }

      /**
       * Adds items onto the end of the array at the path specified.
       *
       * The arguments after `path` and return value match that of
       * `Array.prototype.push`.
       *
       * This method notifies other paths to the same array that a
       * splice occurred to the array.
       *
       * @param {string | !Array<string|number>} path Path to array.
       * @param {...*} items Items to push onto array
       * @return {number} New length of the array.
       * @public
       */
      push(path, ...items) {
        let info = {path: ''};
        let array = /** @type {Array}*/(Polymer.Path.get(this, path, info));
        let len = array.length;
        let ret = array.push(...items);
        if (items.length) {
          notifySplice(this, array, info.path, len, items.length, []);
        }
        return ret;
      }

      /**
       * Removes an item from the end of array at the path specified.
       *
       * The arguments after `path` and return value match that of
       * `Array.prototype.pop`.
       *
       * This method notifies other paths to the same array that a
       * splice occurred to the array.
       *
       * @param {string | !Array<string|number>} path Path to array.
       * @return {*} Item that was removed.
       * @public
       */
      pop(path) {
        let info = {path: ''};
        let array = /** @type {Array} */(Polymer.Path.get(this, path, info));
        let hadLength = Boolean(array.length);
        let ret = array.pop();
        if (hadLength) {
          notifySplice(this, array, info.path, array.length, 0, [ret]);
        }
        return ret;
      }

      /**
       * Starting from the start index specified, removes 0 or more items
       * from the array and inserts 0 or more new items in their place.
       *
       * The arguments after `path` and return value match that of
       * `Array.prototype.splice`.
       *
       * This method notifies other paths to the same array that a
       * splice occurred to the array.
       *
       * @param {string | !Array<string|number>} path Path to array.
       * @param {number} start Index from which to start removing/inserting.
       * @param {number} deleteCount Number of items to remove.
       * @param {...*} items Items to insert into array.
       * @return {Array} Array of removed items.
       * @public
       */
      splice(path, start, deleteCount, ...items) {
        let info = {path : ''};
        let array = /** @type {Array} */(Polymer.Path.get(this, path, info));
        // Normalize fancy native splice handling of crazy start values
        if (start < 0) {
          start = array.length - Math.floor(-start);
        } else {
          start = Math.floor(start);
        }
        if (!start) {
          start = 0;
        }
        let ret = array.splice(start, deleteCount, ...items);
        if (items.length || ret.length) {
          notifySplice(this, array, info.path, start, items.length, ret);
        }
        return ret;
      }

      /**
       * Removes an item from the beginning of array at the path specified.
       *
       * The arguments after `path` and return value match that of
       * `Array.prototype.pop`.
       *
       * This method notifies other paths to the same array that a
       * splice occurred to the array.
       *
       * @param {string | !Array<string|number>} path Path to array.
       * @return {*} Item that was removed.
       * @public
       */
      shift(path) {
        let info = {path: ''};
        let array = /** @type {Array} */(Polymer.Path.get(this, path, info));
        let hadLength = Boolean(array.length);
        let ret = array.shift();
        if (hadLength) {
          notifySplice(this, array, info.path, 0, 0, [ret]);
        }
        return ret;
      }

      /**
       * Adds items onto the beginning of the array at the path specified.
       *
       * The arguments after `path` and return value match that of
       * `Array.prototype.push`.
       *
       * This method notifies other paths to the same array that a
       * splice occurred to the array.
       *
       * @param {string | !Array<string|number>} path Path to array.
       * @param {...*} items Items to insert info array
       * @return {number} New length of the array.
       * @public
       */
      unshift(path, ...items) {
        let info = {path: ''};
        let array = /** @type {Array} */(Polymer.Path.get(this, path, info));
        let ret = array.unshift(...items);
        if (items.length) {
          notifySplice(this, array, info.path, 0, items.length, []);
        }
        return ret;
      }

      /**
       * Notify that a path has changed.
       *
       * Example:
       *
       *     this.item.user.name = 'Bob';
       *     this.notifyPath('item.user.name');
       *
       * @param {string} path Path that should be notified.
       * @param {*=} value Value at the path (optional).
       * @public
      */
      notifyPath(path, value) {
        /** @type {string} */
        let propPath;
        if (arguments.length == 1) {
          // Get value if not supplied
          let info = {path: ''};
          value = Polymer.Path.get(this, path, info);
          propPath = info.path;
        } else if (Array.isArray(path)) {
          // Normalize path if needed
          propPath = Polymer.Path.normalize(path);
        } else {
          propPath = /** @type{string} */(path);
        }
        if (this._setPendingPropertyOrPath(propPath, value, true, true)) {
          this._invalidateProperties();
        }
      }

      /**
       * Equivalent to static `createReadOnlyProperty` API but can be called on
       * an instance to add effects at runtime.  See that method for
       * full API docs.
       *
       * @param {string} property Property name
       * @param {boolean=} protectedSetter Creates a custom protected setter
       *   when `true`.
       * @protected
       */
      _createReadOnlyProperty(property, protectedSetter) {
        this._addPropertyEffect(property, TYPES.READ_ONLY);
        if (protectedSetter) {
          this['_set' + upper(property)] = /** @this {PropertyEffects} */function(value) {
            this._setProperty(property, value);
          }
        }
      }

      /**
       * Equivalent to static `createPropertyObserver` API but can be called on
       * an instance to add effects at runtime.  See that method for
       * full API docs.
       *
       * @param {string} property Property name
       * @param {string} methodName Name of observer method to call
       * @param {boolean=} dynamicFn Whether the method name should be included as
       *   a dependency to the effect.
       * @protected
       */
      _createPropertyObserver(property, methodName, dynamicFn) {
        let info = { property, methodName, dynamicFn: Boolean(dynamicFn) };
        this._addPropertyEffect(property, TYPES.OBSERVE, {
          fn: runObserverEffect, info, trigger: {name: property}
        });
        if (dynamicFn) {
          this._addPropertyEffect(methodName, TYPES.OBSERVE, {
            fn: runObserverEffect, info, trigger: {name: methodName}
          });
        }
      }

      /**
       * Equivalent to static `createMethodObserver` API but can be called on
       * an instance to add effects at runtime.  See that method for
       * full API docs.
       *
       * @param {string} expression Method expression
       * @param {boolean|Object=} dynamicFn Boolean or object map indicating
       *   whether method names should be included as a dependency to the effect.
       * @protected
       */
      _createMethodObserver(expression, dynamicFn) {
        let sig = parseMethod(expression);
        if (!sig) {
          throw new Error("Malformed observer expression '" + expression + "'");
        }
        createMethodEffect(this, sig, TYPES.OBSERVE, runMethodEffect, null, dynamicFn);
      }

      /**
       * Equivalent to static `createNotifyingProperty` API but can be called on
       * an instance to add effects at runtime.  See that method for
       * full API docs.
       *
       * @param {string} property Property name
       * @protected
       */
      _createNotifyingProperty(property) {
        this._addPropertyEffect(property, TYPES.NOTIFY, {
          fn: runNotifyEffect,
          info: {
            eventName: CaseMap.camelToDashCase(property) + '-changed',
            property: property
          }
        });
      }

      /**
       * Equivalent to static `createReflectedProperty` API but can be called on
       * an instance to add effects at runtime.  See that method for
       * full API docs.
       *
       * @param {string} property Property name
       * @protected
       */
      _createReflectedProperty(property) {
        let attr = CaseMap.camelToDashCase(property);
        if (attr[0] === '-') {
          console.warn('Property ' + property + ' cannot be reflected to attribute ' +
            attr + ' because "-" is not a valid starting attribute name. Use a lowercase first letter for the property thisead.');
        } else {
          this._addPropertyEffect(property, TYPES.REFLECT, {
            fn: runReflectEffect,
            info: {
              attrName: attr
            }
          });
        }
      }

      /**
       * Equivalent to static `createComputedProperty` API but can be called on
       * an instance to add effects at runtime.  See that method for
       * full API docs.
       *
       * @param {string} property Name of computed property to set
       * @param {string} expression Method expression
       * @param {boolean|Object=} dynamicFn Boolean or object map indicating
       *   whether method names should be included as a dependency to the effect.
       * @protected
       */
      _createComputedProperty(property, expression, dynamicFn) {
        let sig = parseMethod(expression);
        if (!sig) {
          throw new Error("Malformed computed expression '" + expression + "'");
        }
        createMethodEffect(this, sig, TYPES.COMPUTE, runComputedEffect, property, dynamicFn);
      }

      // -- static class methods ------------

      /**
       * Ensures an accessor exists for the specified property, and adds
       * to a list of "property effects" that will run when the accessor for
       * the specified property is set.  Effects are grouped by "type", which
       * roughly corresponds to a phase in effect processing.  The effect
       * metadata should be in the following form:
       *
       *     {
       *       fn: effectFunction, // Reference to function to call to perform effect
       *       info: { ... }       // Effect metadata passed to function
       *       trigger: {          // Optional triggering metadata; if not provided
       *         name: string      // the property is treated as a wildcard
       *         structured: boolean
       *         wildcard: boolean
       *       }
       *     }
       *
       * Effects are called from `_propertiesChanged` in the following order by
       * type:
       *
       * 1. COMPUTE
       * 2. PROPAGATE
       * 3. REFLECT
       * 4. OBSERVE
       * 5. NOTIFY
       *
       * Effect functions are called with the following signature:
       *
       *     effectFunction(inst, path, props, oldProps, info, hasPaths)
       *
       * @param {string} property Property that should trigger the effect
       * @param {string} type Effect type, from this.PROPERTY_EFFECT_TYPES
       * @param {Object=} effect Effect metadata object
       * @protected
       */
      static addPropertyEffect(property, type, effect) {
        this.prototype._addPropertyEffect(property, type, effect);
      }

      /**
       * Creates a single-property observer for the given property.
       *
       * @param {string} property Property name
       * @param {string} methodName Name of observer method to call
       * @param {boolean=} dynamicFn Whether the method name should be included as
       *   a dependency to the effect.
       * @protected
       */
      static createPropertyObserver(property, methodName, dynamicFn) {
        this.prototype._createPropertyObserver(property, methodName, dynamicFn);
      }

      /**
       * Creates a multi-property "method observer" based on the provided
       * expression, which should be a string in the form of a normal Javascript
       * function signature: `'methodName(arg1, [..., argn])'`.  Each argument
       * should correspond to a property or path in the context of this
       * prototype (or instance), or may be a literal string or number.
       *
       * @param {string} expression Method expression
       * @param {boolean|Object=} dynamicFn Boolean or object map indicating
       *   whether method names should be included as a dependency to the effect.
       * @protected
       */
      static createMethodObserver(expression, dynamicFn) {
        this.prototype._createMethodObserver(expression, dynamicFn);
      }

      /**
       * Causes the setter for the given property to dispatch `<property>-changed`
       * events to notify of changes to the property.
       *
       * @param {string} property Property name
       * @protected
       */
      static createNotifyingProperty(property) {
        this.prototype._createNotifyingProperty(property);
      }

      /**
       * Creates a read-only accessor for the given property.
       *
       * To set the property, use the protected `_setProperty` API.
       * To create a custom protected setter (e.g. `_setMyProp()` for
       * property `myProp`), pass `true` for `protectedSetter`.
       *
       * Note, if the property will have other property effects, this method
       * should be called first, before adding other effects.
       *
       * @param {string} property Property name
       * @param {boolean=} protectedSetter Creates a custom protected setter
       *   when `true`.
       * @protected
       */
      static createReadOnlyProperty(property, protectedSetter) {
        this.prototype._createReadOnlyProperty(property, protectedSetter);
      }

      /**
       * Causes the setter for the given property to reflect the property value
       * to a (dash-cased) attribute of the same name.
       *
       * @param {string} property Property name
       * @protected
       */
      static createReflectedProperty(property) {
        this.prototype._createReflectedProperty(property);
      }

      /**
       * Creates a computed property whose value is set to the result of the
       * method described by the given `expression` each time one or more
       * arguments to the method changes.  The expression should be a string
       * in the form of a normal Javascript function signature:
       * `'methodName(arg1, [..., argn])'`
       *
       * @param {string} property Name of computed property to set
       * @param {string} expression Method expression
       * @param {boolean|Object=} dynamicFn Boolean or object map indicating whether
       *   method names should be included as a dependency to the effect.
       * @protected
       */
      static createComputedProperty(property, expression, dynamicFn) {
        this.prototype._createComputedProperty(property, expression, dynamicFn);
      }

      /**
       * Parses the provided template to ensure binding effects are created
       * for them, and then ensures property accessors are created for any
       * dependent properties in the template.  Binding effects for bound
       * templates are stored in a linked list on the instance so that
       * templates can be efficiently stamped and unstamped.
       *
       * @param {HTMLTemplateElement} template Template containing binding
       *   bindings
       * @return {Object} Template metadata object
       * @protected
       */
      static bindTemplate(template) {
        return this.prototype._bindTemplate(template);
      }

      // -- binding ----------------------------------------------

      /**
       * Equivalent to static `bindTemplate` API but can be called on
       * an instance to add effects at runtime.  See that method for
       * full API docs.
       *
       * This method may be called on the prototype (for prototypical template
       * binding, to avoid creating accessors every instance) once per prototype,
       * and will be called with `runtimeBinding: true` by `_stampTemplate` to
       * create and link an instance of the template metadata associated with a
       * particular stamping.
       *
       * @param {HTMLTemplateElement} template Template containing binding
       *   bindings
       * @param {boolean=} instanceBinding When false (default), performs
       *   "prototypical" binding of the template and overwrites any previously
       *   bound template for the class. When true (as passed from
       *   `_stampTemplate`), the template info is instanced and linked into
       *   the list of bound templates.
       * @return {!TemplateInfo} Template metadata object; for `runtimeBinding`,
       *   this is an instance of the prototypical template info
       * @protected
       */
      _bindTemplate(template, instanceBinding) {
        let templateInfo = this.constructor._parseTemplate(template);
        let wasPreBound = this.__templateInfo == templateInfo;
        // Optimization: since this is called twice for proto-bound templates,
        // don't attempt to recreate accessors if this template was pre-bound
        if (!wasPreBound) {
          for (let prop in templateInfo.propertyEffects) {
            this._createPropertyAccessor(prop);
          }
        }
        if (instanceBinding) {
          // For instance-time binding, create instance of template metadata
          // and link into list of templates if necessary
          templateInfo = /** @type {!TemplateInfo} */(Object.create(templateInfo));
          templateInfo.wasPreBound = wasPreBound;
          if (!wasPreBound && this.__templateInfo) {
            let last = this.__templateInfoLast || this.__templateInfo;
            this.__templateInfoLast = last.nextTemplateInfo = templateInfo;
            templateInfo.previousTemplateInfo = last;
            return templateInfo;
          }
        }
        return this.__templateInfo = templateInfo;
      }

      /**
       * Adds a property effect to the given template metadata, which is run
       * at the "propagate" stage of `_propertiesChanged` when the template
       * has been bound to the element via `_bindTemplate`.
       *
       * The `effect` object should match the format in `_addPropertyEffect`.
       *
       * @param {Object} templateInfo Template metadata to add effect to
       * @param {string} prop Property that should trigger the effect
       * @param {Object=} effect Effect metadata object
       * @protected
       */
      static _addTemplatePropertyEffect(templateInfo, prop, effect) {
        let hostProps = templateInfo.hostProps = templateInfo.hostProps || {};
        hostProps[prop] = true;
        let effects = templateInfo.propertyEffects = templateInfo.propertyEffects || {};
        let propEffects = effects[prop] = effects[prop] || [];
        propEffects.push(effect);
      }

      /**
       * Stamps the provided template and performs instance-time setup for
       * Polymer template features, including data bindings, declarative event
       * listeners, and the `this.$` map of `id`'s to nodes.  A document fragment
       * is returned containing the stamped DOM, ready for insertion into the
       * DOM.
       *
       * This method may be called more than once; however note that due to
       * `shadycss` polyfill limitations, only styles from templates prepared
       * using `ShadyCSS.prepareTemplate` will be correctly polyfilled (scoped
       * to the shadow root and support CSS custom properties), and note that
       * `ShadyCSS.prepareTemplate` may only be called once per element. As such,
       * any styles required by in runtime-stamped templates must be included
       * in the main element template.
       *
       * @param {!HTMLTemplateElement} template Template to stamp
       * @return {!StampedTemplate} Cloned template content
       * @override
       * @protected
       */
      _stampTemplate(template) {
        // Ensures that created dom is `_enqueueClient`'d to this element so
        // that it can be flushed on next call to `_flushProperties`
        hostStack.beginHosting(this);
        let dom = super._stampTemplate(template);
        hostStack.endHosting(this);
        let templateInfo = /** @type {!TemplateInfo} */(this._bindTemplate(template, true));
        // Add template-instance-specific data to instanced templateInfo
        templateInfo.nodeList = dom.nodeList;
        // Capture child nodes to allow unstamping of non-prototypical templates
        if (!templateInfo.wasPreBound) {
          let nodes = templateInfo.childNodes = [];
          for (let n=dom.firstChild; n; n=n.nextSibling) {
            nodes.push(n);
          }
        }
        dom.templateInfo = templateInfo;
        // Setup compound storage, 2-way listeners, and dataHost for bindings
        setupBindings(this, templateInfo);
        // Flush properties into template nodes if already booted
        if (this.__dataReady) {
          runEffects(this, templateInfo.propertyEffects, this.__data, null,
            false, templateInfo.nodeList);
        }
        return dom;
      }

      /**
       * Removes and unbinds the nodes previously contained in the provided
       * DocumentFragment returned from `_stampTemplate`.
       *
       * @param {!StampedTemplate} dom DocumentFragment previously returned
       *   from `_stampTemplate` associated with the nodes to be removed
       * @protected
       */
      _removeBoundDom(dom) {
        // Unlink template info
        let templateInfo = dom.templateInfo;
        if (templateInfo.previousTemplateInfo) {
          templateInfo.previousTemplateInfo.nextTemplateInfo =
            templateInfo.nextTemplateInfo;
        }
        if (templateInfo.nextTemplateInfo) {
          templateInfo.nextTemplateInfo.previousTemplateInfo =
            templateInfo.previousTemplateInfo;
        }
        if (this.__templateInfoLast == templateInfo) {
          this.__templateInfoLast = templateInfo.previousTemplateInfo;
        }
        templateInfo.previousTemplateInfo = templateInfo.nextTemplateInfo = null;
        // Remove stamped nodes
        let nodes = templateInfo.childNodes;
        for (let i=0; i<nodes.length; i++) {
          let node = nodes[i];
          node.parentNode.removeChild(node);
        }
      }

      /**
       * Overrides default `TemplateStamp` implementation to add support for
       * parsing bindings from `TextNode`'s' `textContent`.  A `bindings`
       * array is added to `nodeInfo` and populated with binding metadata
       * with information capturing the binding target, and a `parts` array
       * with one or more metadata objects capturing the source(s) of the
       * binding.
       *
       * @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 _parseTemplateNode(node, templateInfo, nodeInfo) {
        let noted = super._parseTemplateNode(node, templateInfo, nodeInfo);
        if (node.nodeType === Node.TEXT_NODE) {
          let parts = this._parseBindings(node.textContent, templateInfo);
          if (parts) {
            // Initialize the textContent with any literal parts
            // NOTE: default to a space here so the textNode remains; some browsers
            // (IE) evacipate an empty textNode following cloneNode/importNode.
            node.textContent = literalFromParts(parts) || ' ';
            addBinding(this, templateInfo, nodeInfo, 'text', 'textContent', parts);
            noted = true;
          }
        }
        return noted;
      }

      /**
       * Overrides default `TemplateStamp` implementation to add support for
       * parsing bindings from attributes.  A `bindings`
       * array is added to `nodeInfo` and populated with binding metadata
       * with information capturing the binding target, and a `parts` array
       * with one or more metadata objects capturing the source(s) of the
       * binding.
       *
       * @override
       * @param {Element} 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) {
        let parts = this._parseBindings(value, templateInfo);
        if (parts) {
          // Attribute or property
          let origName = name;
          let kind = 'property';
          if (name[name.length-1] == '$') {
            name = name.slice(0, -1);
            kind = 'attribute';
          }
          // Initialize attribute bindings with any literal parts
          let literal = literalFromParts(parts);
          if (literal && kind == 'attribute') {
            node.setAttribute(name, literal);
          }
          // Clear attribute before removing, since IE won't allow removing
          // `value` attribute if it previously had a value (can't
          // unconditionally set '' before removing since attributes with `$`
          // can't be set using setAttribute)
          if (node.localName === 'input' && origName === 'value') {
            node.setAttribute(origName, '');
          }
          // Remove annotation
          node.removeAttribute(origName);
          // Case hackery: attributes are lower-case, but bind targets
          // (properties) are case sensitive. Gambit is to map dash-case to
          // camel-case: `foo-bar` becomes `fooBar`.
          // Attribute bindings are excepted.
          if (kind === 'property') {
            name = Polymer.CaseMap.dashToCamelCase(name);
          }
          addBinding(this, templateInfo, nodeInfo, kind, name, parts, literal);
          return true;
        } else {
          return super._parseTemplateNodeAttribute(node, templateInfo, nodeInfo, name, value);
        }
      }

      /**
       * Overrides default `TemplateStamp` implementation to add support for
       * binding the properties that a nested template depends on to the template
       * as `_host_<property>`.
       *
       * @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 _parseTemplateNestedTemplate(node, templateInfo, nodeInfo) {
        let noted = super._parseTemplateNestedTemplate(node, templateInfo, nodeInfo);
        // Merge host props into outer template and add bindings
        let hostProps = nodeInfo.templateInfo.hostProps;
        let mode = '{';
        for (let source in hostProps) {
          let parts = [{ mode, source, dependencies: [source] }];
          addBinding(this, templateInfo, nodeInfo, 'property', '_host_' + source, parts);
        }
        return noted;
      }

      /**
       * Called to parse text in a template (either attribute values or
       * textContent) into binding metadata.
       *
       * Any overrides of this method should return an array of binding part
       * metadata  representing one or more bindings found in the provided text
       * and any "literal" text in between.  Any non-literal parts will be passed
       * to `_evaluateBinding` when any dependencies change.  The only required
       * fields of each "part" in the returned array are as follows:
       *
       * - `dependencies` - Array containing trigger metadata for each property
       *   that should trigger the binding to update
       * - `literal` - String containing text if the part represents a literal;
       *   in this case no `dependencies` are needed
       *
       * Additional metadata for use by `_evaluateBinding` may be provided in
       * each part object as needed.
       *
       * The default implementation handles the following types of bindings
       * (one or more may be intermixed with literal strings):
       * - Property binding: `[[prop]]`
       * - Path binding: `[[object.prop]]`
       * - Negated property or path bindings: `[[!prop]]` or `[[!object.prop]]`
       * - Two-way property or path bindings (supports negation):
       *   `{{prop}}`, `{{object.prop}}`, `{{!prop}}` or `{{!object.prop}}`
       * - Inline computed method (supports negation):
       *   `[[compute(a, 'literal', b)]]`, `[[!compute(a, 'literal', b)]]`
       *
       * @param {string} text Text to parse from attribute or textContent
       * @param {Object} templateInfo Current template metadata
       * @return {Array<!BindingPart>} Array of binding part metadata
       * @protected
       */
      static _parseBindings(text, templateInfo) {
        let parts = [];
        let lastIndex = 0;
        let m;
        // Example: "literal1{{prop}}literal2[[!compute(foo,bar)]]final"
        // Regex matches:
        //        Iteration 1:  Iteration 2:
        // m[1]: '{{'          '[['
        // m[2]: ''            '!'
        // m[3]: 'prop'        'compute(foo,bar)'
        while ((m = bindingRegex.exec(text)) !== null) {
          // Add literal part
          if (m.index > lastIndex) {
            parts.push({literal: text.slice(lastIndex, m.index)});
          }
          // Add binding part
          let mode = m[1][0];
          let negate = Boolean(m[2]);
          let source = m[3].trim();
          let customEvent = false, notifyEvent = '', colon = -1;
          if (mode == '{' && (colon = source.indexOf('::')) > 0) {
            notifyEvent = source.substring(colon + 2);
            source = source.substring(0, colon);
            customEvent = true;
          }
          let signature = parseMethod(source);
          let dependencies = [];
          if (signature) {
            // Inline computed function
            let {args, methodName} = signature;
            for (let i=0; i<args.length; i++) {
              let arg = args[i];
              if (!arg.literal) {
                dependencies.push(arg);
              }
            }
            let dynamicFns = templateInfo.dynamicFns;
            if (dynamicFns && dynamicFns[methodName] || signature.static) {
              dependencies.push(methodName);
              signature.dynamicFn = true;
            }
          } else {
            // Property or path
            dependencies.push(source);
          }
          parts.push({
            source, mode, negate, customEvent, signature, dependencies,
            event: notifyEvent
          });
          lastIndex = bindingRegex.lastIndex;
        }
        // Add a final literal part
        if (lastIndex && lastIndex < text.length) {
          let literal = text.substring(lastIndex);
          if (literal) {
            parts.push({
              literal: literal
            });
          }
        }
        if (parts.length) {
          return parts;
        } else {
          return null;
        }
      }

      /**
       * Called to evaluate a previously parsed binding part based on a set of
       * one or more changed dependencies.
       *
       * @param {this} inst Element that should be used as scope for
       *   binding dependencies
       * @param {BindingPart} part Binding part metadata
       * @param {string} path Property/path that triggered this effect
       * @param {Object} props Bag of current property changes
       * @param {Object} oldProps Bag of previous values for changed properties
       * @param {boolean} hasPaths True with `props` contains one or more paths
       * @return {*} Value the binding part evaluated to
       * @protected
       */
      static _evaluateBinding(inst, part, path, props, oldProps, hasPaths) {
        let value;
        if (part.signature) {
          value = runMethodEffect(inst, path, props, oldProps, part.signature);
        } else if (path != part.source) {
          value = Polymer.Path.get(inst, part.source);
        } else {
          if (hasPaths && Polymer.Path.isPath(path)) {
            value = Polymer.Path.get(inst, path);
          } else {
            value = inst.__data[path];
          }
        }
        if (part.negate) {
          value = !value;
        }
        return value;
      }

    }

    // make a typing for closure :P
    PropertyEffectsType = PropertyEffects;

    return PropertyEffects;
  });

  /**
   * Helper api for enqueing client dom created by a host element.
   *
   * By default elements are flushed via `_flushProperties` when
   * `connectedCallback` is called. Elements attach their client dom to
   * themselves at `ready` time which results from this first flush.
   * This provides an ordering guarantee that the client dom an element
   * creates is flushed before the element itself (i.e. client `ready`
   * fires before host `ready`).
   *
   * However, if `_flushProperties` is called *before* an element is connected,
   * as for example `Templatize` does, this ordering guarantee cannot be
   * satisfied because no elements are connected. (Note: Bound elements that
   * receive data do become enqueued clients and are properly ordered but
   * unbound elements are not.)
   *
   * To maintain the desired "client before host" ordering guarantee for this
   * case we rely on the "host stack. Client nodes registers themselves with
   * the creating host element when created. This ensures that all client dom
   * is readied in the proper order, maintaining the desired guarantee.
   *
   * @private
   */
  let hostStack = {

    stack: [],

    /**
     * @param {*} inst Instance to add to hostStack
     * @this {hostStack}
     */
    registerHost(inst) {
      if (this.stack.length) {
        let host = this.stack[this.stack.length-1];
        host._enqueueClient(inst);
      }
    },

    /**
     * @param {*} inst Instance to begin hosting
     * @this {hostStack}
     */
    beginHosting(inst) {
      this.stack.push(inst);
    },

    /**
     * @param {*} inst Instance to end hosting
     * @this {hostStack}
     */
    endHosting(inst) {
      let stackLen = this.stack.length;
      if (stackLen && this.stack[stackLen-1] == inst) {
        this.stack.pop();
      }
    }

  }

})();
</script>