420 lines
13 KiB
JavaScript
420 lines
13 KiB
JavaScript
/**
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* Handles building members (properties, methods)
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*
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* This prototype could have easily been refactored into a number of others
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* (e.g. one for each type of member), but that refactoring has been deferred
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* until necessary to ensure ease.js maintains a relatively small footprint.
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* Ultimately, however, such a decision is a micro-optimization and shouldn't
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* harm the design and maintainability of the software.
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*
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* TODO: Implementation is inconsistent between various members. For example,
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* methods use ___$$keywords$$, whereas properties use [ val, keywords ]. Decide
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* on a common format.
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*
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* Copyright (C) 2010 Mike Gerwitz
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*
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* This file is part of ease.js.
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*
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* ease.js is free software: you can redistribute it and/or modify it under the
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* terms of the GNU Lesser General Public License as published by the Free
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* Software Foundation, either version 3 of the License, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
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* for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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* @author Mike Gerwitz
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* @package core
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*/
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var util = require( __dirname + '/util' ),
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Warning = require( __dirname + '/warn' ).Warning,
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visibility = [ 'public', 'protected', 'private' ]
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;
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/**
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* Responsible for building class members
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*/
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module.exports = function MemberBuilder( wrap_method, wrap_override, validate )
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{
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// permit omitting 'new' keyword
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if ( !( this instanceof module.exports ) )
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{
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return new module.exports( wrap_method, wrap_override, validate );
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}
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this._wrapMethod = wrap_method;
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this._wrapOverride = wrap_override;
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this._validate = validate;
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};
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// we're throwing everything into the prototype
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exports = module.exports.prototype;
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/**
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* Initializes member object
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*
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* The member object contains members for each level of visibility (public,
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* protected and private).
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*
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* @param {Object} mpublic default public members
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* @param {Object} mprotected default protected members
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* @param {Object} mprivate default private members
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*
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* @return {{public: Object, protected: Object, private: Object}}
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*/
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exports.initMembers = function( mpublic, mprotected, mprivate )
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{
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return {
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'public': mpublic || {},
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'protected': mprotected || {},
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'private': mprivate || {},
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};
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};
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/**
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* Copies a method to the appropriate member prototype, depending on
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* visibility, and assigns necessary metadata from keywords
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*
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* @param {{public: Object, protected: Object, private: Object}} members
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*
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* @param {Object} meta metadata container
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* @param {string} name property name
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* @param {*} value property value
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*
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* @param {Object.<string,boolean>} keywords parsed keywords
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* @param {Object=} instCallback function to call in order to retrieve
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* object to bind 'this' keyword to
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* @param {number} cid class id
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*
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* @return {undefined}
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*/
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exports.buildMethod = function(
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members, meta, name, value, keywords, instCallback, cid, base
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)
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{
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// TODO: We can improve performance by not scanning each one individually
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// every time this method is called
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var prev_data = scanMembers( members, name, base ),
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prev = ( prev_data ) ? prev_data.member : null,
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prev_keywords = ( prev && prev.___$$keywords$$ ),
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dest = getMemberVisibility( members, keywords, name );
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;
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// ensure that the declaration is valid (keywords make sense, argument
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// length, etc)
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this._validate.validateMethod(
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name, value, keywords, prev_data, prev_keywords
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);
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// we might be overriding an existing method
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if ( prev )
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{
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// TODO: warning if no super method when override keyword provided
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if ( keywords[ 'override' ] || prev_keywords[ 'abstract' ] )
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{
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// override the method
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dest[ name ] = this._overrideMethod(
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prev, value, instCallback, cid
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);
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}
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else
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{
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// by default, perform method hiding, even if the keyword was not
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// provided (the keyword simply suppresses the warning)
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dest[ name ] = hideMethod( prev, value, instCallback, cid );
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}
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}
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else if ( keywords[ 'abstract' ] )
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{
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// we do not want to wrap abstract methods, since they are not callable
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dest[ name ] = value;
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}
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else
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{
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// we are not overriding the method, so simply copy it over, wrapping it
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// to ensure privileged calls will work properly
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dest[ name ] = this._overrideMethod( null, value, instCallback, cid );
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}
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// store keywords for later reference (needed for pre-ES5 fallback)
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dest[ name ].___$$keywords$$ = keywords;
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};
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/**
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* Copies a property to the appropriate member prototype, depending on
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* visibility, and assigns necessary metadata from keywords
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*
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* @param {{public: Object, protected: Object, private: Object}} members
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*
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* @param {Object} meta metadata container
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* @param {string} name property name
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* @param {*} value property value
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*
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* @param {Object.<string,boolean>} keywords parsed keywords
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* @param {Object=} base optional base object to scan
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*
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* @return {undefined}
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*/
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exports.buildProp = function( members, meta, name, value, keywords, base )
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{
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// TODO: We can improve performance by not scanning each one individually
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// every time this method is called
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var prev_data = scanMembers( members, name, base ),
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prev = ( prev_data ) ? prev_data.member : null,
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prev_keywords = ( prev ) ? prev[ 1 ] : null;
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this._validate.validateProperty(
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name, value, keywords, prev_data, prev_keywords
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);
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getMemberVisibility( members, keywords, name )[ name ] =
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[ value, keywords ];
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};
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/**
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* Copies a getter/setter to the appropriate member prototype, depending on
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* visibility, and assigns necessary metadata from keywords
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*
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* @param {{public: Object, protected: Object, private: Object}} members
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*
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* @param {Object} meta metadata container
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* @param {string} name getter name
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* @param {*} get getter value
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* @param {*} set setter value
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*
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* @param {Object.<string,boolean>} keywords parsed keywords
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*
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* @param {Object=} base optional base object to scan
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*
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* @return {undefined}
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*/
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exports.buildGetterSetter = function(
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members, meta, name, get, set, keywords, base
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)
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{
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var prev_data = scanMembers( members, name, base ),
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prev_keywords = {}
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;
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this._validate.validateGetterSetter(
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name, keywords, prev_data, prev_keywords
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);
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Object.defineProperty(
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getMemberVisibility( members, keywords, name ),
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name,
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{
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get: get,
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set: set,
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enumerable: true,
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configurable: false,
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}
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);
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};
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/**
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* Returns member prototype to use for the requested visibility
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*
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* Will throw an exception if multiple access modifiers were used.
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*
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* @param {{public: Object, protected: Object, private: Object}} members
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*
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* @param {Object.<string,boolean>} keywords parsed keywords
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* @param {string} name member name
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*
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* @return {Object} reference to visibility of members argument to use
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*/
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function getMemberVisibility( members, keywords, name )
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{
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var viserr = function()
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{
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throw TypeError(
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"Only one access modifier may be used for definition of '" +
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name + "'"
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);
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}
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// there's cleaner ways of doing this, but consider it loop unrolling for
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// performance
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if ( keywords[ 'private' ] )
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{
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( keywords[ 'public' ] || keywords[ 'protected' ] ) && viserr();
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return members[ 'private' ];
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}
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else if ( keywords[ 'protected' ] )
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{
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( keywords[ 'public' ] || keywords[ 'private' ] ) && viserr();
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return members[ 'protected' ];
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}
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else
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{
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// public keyword is the default, so explicitly specifying it is only
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// for clarity
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( keywords[ 'private' ] || keywords[ 'protected' ] ) && viserr();
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return members[ 'public' ];
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}
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}
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/**
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* Scan each level of visibility for the requested member
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*
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* @param {{public: Object, protected: Object, private: Object}} members
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*
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* @param {string} name member to locate
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* @param {Object=} base optional base object to scan
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*
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* @return {Object} Array of member and number corresponding to visibility,
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* level if located, otherwise an empty object
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*/
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function scanMembers( members, name, base )
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{
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var i = visibility.length,
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member = null;
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// locate requested member by scanning each level of visibility
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while ( i-- )
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{
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var visobj = members[ visibility[ i ] ];
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// In order to support getters/setters, we must go off of the
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// descriptor. We must also ignore base properties (last argument), such
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// as Object.prototype.toString(). However, we must still traverse the
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// prototype chain.
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if ( member = util.getPropertyDescriptor( visobj, name, true ) )
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{
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return {
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get: member.get,
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set: member.set,
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member: member.value,
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};
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}
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}
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// if a second comparison object was given, try again using it instead of
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// the original members object
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if ( base !== undefined )
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{
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var base_methods = base.___$$methods$$,
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base_props = base.___$$props$$;
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// scan the base's methods and properties, if they are available
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return ( base_methods && scanMembers( base_methods, name ) )
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|| ( base_props && scanMembers( base_props, name ) )
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|| null
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;
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}
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// nothing was found
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return null;
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}
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/**
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* Hide a method with a "new" method
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*/
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function hideMethod( super_method, new_method, instCallback, cid )
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{
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// TODO: This function is currently unimplemented. It exists at present to
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// provide a placeholder and ensure that the override keyword is required to
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// override a parent method.
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//
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// We should never get to this point if the default validation rule set is
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// used to prevent omission of the 'override' keyword.
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throw Error(
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'Method hiding not yet implemented (we should never get here; bug).'
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);
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}
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/**
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* Generates a method override function
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*
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* The override function simply wraps the method so that its invocation will
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* pass a __super property. This property may be used to invoke the overridden
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* method.
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*
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* @param {function()} super_method method to override
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* @param {function()} new_method method to override with
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*
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* @param {Object=} instCallback function to call in order to retrieve
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* object to bind 'this' keyword to
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* @param {number} cid class id
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*
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* @return {function()} override method
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*/
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exports._overrideMethod = function(
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super_method, new_method, instCallback, cid
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)
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{
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instCallback = instCallback || function() {};
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// return a function that permits referencing the super method via the
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// __super property
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var override = null;
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// are we overriding?
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override = (
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( super_method )
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? this._wrapOverride
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: this._wrapMethod
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).wrapMethod( new_method, super_method, cid, instCallback );
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// This is a trick to work around the fact that we cannot set the length
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// property of a function. Instead, we define our own property - __length.
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// This will store the expected number of arguments from the super method.
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// This way, when a method is being overridden, we can check to ensure its
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// compatibility with its super method.
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util.defineSecureProp( override,
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'__length',
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( new_method.__length || new_method.length )
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);
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return override;
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}
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/**
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* Return the visibility level as a numeric value, where 0 is public and 2 is
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* private
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*
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* @param {Object} keywords keywords to scan for visibility level
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*
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* @return {number} visibility level as a numeric value
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*/
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exports._getVisibilityValue = function( keywords )
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{
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if ( keywords[ 'protected' ] )
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{
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return 1;
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}
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else if ( keywords[ 'private' ] )
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{
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return 2;
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}
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else
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{
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// default is public
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return 0;
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}
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}
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