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// Copyright 2009 The Closure Library Authors. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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//      http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS-IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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/**
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 * @fileoverview Useful compiler idioms.
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 *
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 * @author [email protected] (John Lenz)
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 */
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goog.provide('goog.reflect');
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/**
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 * Syntax for object literal casts.
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 * @see http://go/jscompiler-renaming
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 * @see https://goo.gl/CRs09P
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 *
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 * Use this if you have an object literal whose keys need to have the same names
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 * as the properties of some class even after they are renamed by the compiler.
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 *
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 * @param {!Function} type Type to cast to.
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 * @param {Object} object Object literal to cast.
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 * @return {Object} The object literal.
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 */
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goog.reflect.object = function(type, object) {
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  return object;
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};
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/**
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 * Syntax for renaming property strings.
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 * @see http://go/jscompiler-renaming
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 * @see https://goo.gl/CRs09P
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 *
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 * Use this if you have an need to access a property as a string, but want
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 * to also have the property renamed by the compiler. In contrast to
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 * goog.reflect.object, this method takes an instance of an object.
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 *
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 * Properties must be simple names (not qualified names).
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 *
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 * @param {string} prop Name of the property
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 * @param {!Object} object Instance of the object whose type will be used
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 *     for renaming
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 * @return {string} The renamed property.
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 */
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goog.reflect.objectProperty = function(prop, object) {
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  return prop;
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};
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/**
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 * To assert to the compiler that an operation is needed when it would
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 * otherwise be stripped. For example:
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 * <code>
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 *     // Force a layout
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 *     goog.reflect.sinkValue(dialog.offsetHeight);
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 * </code>
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 * @param {T} x
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 * @return {T}
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 * @template T
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 */
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goog.reflect.sinkValue = function(x) {
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  goog.reflect.sinkValue[' '](x);
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  return x;
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};
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/**
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 * The compiler should optimize this function away iff no one ever uses
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 * goog.reflect.sinkValue.
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 */
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goog.reflect.sinkValue[' '] = goog.nullFunction;
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/**
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 * Check if a property can be accessed without throwing an exception.
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 * @param {Object} obj The owner of the property.
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 * @param {string} prop The property name.
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 * @return {boolean} Whether the property is accessible. Will also return true
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 *     if obj is null.
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 */
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goog.reflect.canAccessProperty = function(obj, prop) {
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  try {
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    goog.reflect.sinkValue(obj[prop]);
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    return true;
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  } catch (e) {
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  }
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  return false;
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};
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/**
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 * Retrieves a value from a cache given a key. The compiler provides special
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 * consideration for this call such that it is generally considered side-effect
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 * free. However, if the {@code opt_keyFn} or {@code valueFn} have side-effects
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 * then the entire call is considered to have side-effects.
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 *
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 * Conventionally storing the value on the cache would be considered a
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 * side-effect and preclude unused calls from being pruned, ie. even if
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 * the value was never used, it would still always be stored in the cache.
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 *
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 * Providing a side-effect free {@code valueFn} and {@code opt_keyFn}
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 * allows unused calls to {@code goog.reflect.cache} to be pruned.
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 *
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 * @param {!Object<K, V>} cacheObj The object that contains the cached values.
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 * @param {?} key The key to lookup in the cache. If it is not string or number
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 *     then a {@code opt_keyFn} should be provided. The key is also used as the
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 *     parameter to the {@code valueFn}.
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 * @param {function(?):V} valueFn The value provider to use to calculate the
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 *     value to store in the cache. This function should be side-effect free
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 *     to take advantage of the optimization.
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 * @param {function(?):K=} opt_keyFn The key provider to determine the cache
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 *     map key. This should be used if the given key is not a string or number.
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 *     If not provided then the given key is used. This function should be
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 *     side-effect free to take advantage of the optimization.
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 * @return {V} The cached or calculated value.
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 * @template K
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 * @template V
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 */
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goog.reflect.cache = function(cacheObj, key, valueFn, opt_keyFn) {
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  var storedKey = opt_keyFn ? opt_keyFn(key) : key;
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  if (Object.prototype.hasOwnProperty.call(cacheObj, storedKey)) {
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    return cacheObj[storedKey];
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  }
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  return (cacheObj[storedKey] = valueFn(key));
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};
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