495 lines
15 KiB
JavaScript
495 lines
15 KiB
JavaScript
/**
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* Handles building members (properties, methods)
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*
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* Copyright (C) 2010, 2011, 2012, 2013 Mike Gerwitz
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*
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* This file is part of GNU ease.js.
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*
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* ease.js is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU 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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* 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
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* deferred until necessary to ensure ease.js maintains a relatively small
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* footprint. Ultimately, however, such a decision is a micro-optimization
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* and shouldn't harm the design and maintainability of the software.
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*
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* TODO: Implementation is inconsistent between various members. For
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* example, methods use ___$$keywords$$, whereas properties use [ val,
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* keywords ]. Decide on a common format.
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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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* @param {Function} wrap_method method wrapper
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* @param {Function} wrap_override method override wrapper
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* @param {Function} wrap_proxy method proxy wrapper
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* @param {MemberBuilderValidator} validate member validator
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*
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* @constructor
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*/
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module.exports = function MemberBuilder(
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wrap_method, wrap_override, wrap_proxy, validate
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)
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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(
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wrap_method, wrap_override, wrap_proxy, validate
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);
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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._wrapProxy = wrap_proxy;
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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 {__visobj}
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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 {__visobj} members
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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.<boolean>} keywords parsed keywords
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*
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* @param {Function} instCallback function to call in order to retrieve
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* object to bind 'this' keyword to
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*
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* @param {number} cid class id
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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.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 ( keywords[ 'proxy' ] )
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{
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// TODO: Note that this is not compatible with method hiding, due to its
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// positioning (see hideMethod() below); address once method hiding is
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// implemented (the validators currently handle everything else)
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dest[ name ] = this._createProxy(
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value, instCallback, cid, name, keywords
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);
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}
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else if ( prev )
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{
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if ( keywords.weak )
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{
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// another member of the same name has been found; discard the
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// weak declaration
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return false;
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}
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else 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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return true;
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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 {__visobj} members
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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.<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.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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* TODO: This should essentially mirror buildMethod with regards to overrides,
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* proxies, etc.
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*
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* @param {!__visobj} members
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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.<boolean>} keywords parsed keywords
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*
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* @param {Function} instCallback function to call in order to retrieve
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* object to bind 'this' keyword to
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*
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* @param {number} cid class id
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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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* Closure Compiler is improperly throwing warnings on Object.defineProperty():
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* @suppress {checkTypes}
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*/
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exports.buildGetterSetter = function(
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members, meta, name, get, set, keywords, instCallback, cid, 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 = ( ( prev_data && prev_data.get )
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? prev_data.get.___$$keywords$$
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: null
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)
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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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if ( get )
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{
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get = this._overrideMethod( null, get, instCallback, cid );
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// ensure we store the keywords *after* the override, otherwise they
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// will be assigned to the wrapped function (the getter)
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get.___$$keywords$$ = 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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? this._overrideMethod( null, set, instCallback, cid )
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: 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 {__visobj} members
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*
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* @param {!Object.<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 {__visobj} 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 {{get,set,member}|null}
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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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// we must recurse on *all* the visibility objects of the base's
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// supertype; attempt to find the class associated with its
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// supertype, if any
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var base2 = ( ( base.prototype || {} ).___$$parent$$ || {} )
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.constructor;
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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, base2 ) )
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|| ( base_props && scanMembers( base_props, name, base2 ) )
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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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* Create a method that proxies to the method of another object
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*
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* @param {string} proxy_to name of property (of instance) to proxy to
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*
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* @param {Function} instCallback function to call in order to retrieve
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* object to bind 'this' keyword to
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*
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* @param {number} cid class id
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* @param {string} mname name of method to invoke on destination object
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* @param {Object} keywords method keywords
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*
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* @return {Function} proxy method
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*/
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exports._createProxy = function( proxy_to, instCallback, cid, mname, keywords )
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{
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return this._wrapProxy.wrapMethod(
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proxy_to, null, cid, instCallback, mname, keywords
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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 {Function} instCallback function to call in order to retrieve
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* object to bind 'this' keyword to
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*
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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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