544 lines
16 KiB
JavaScript
544 lines
16 KiB
JavaScript
/**
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* Handles building members (properties, methods)
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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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fallback = util.definePropertyFallback(),
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visibility = [ 'public', 'protected', 'private' ];
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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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dest = getMemberVisibility( members, keywords );
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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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validateMethod( keywords, prev_data, value, name );
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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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// override the method
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dest[ name ] = overrideMethod( prev, value, instCallback, cid );
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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 ] = overrideMethod( value, null, 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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* Validates a method declaration, ensuring that keywords are valid, overrides
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* make sense, etc.
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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} prev_data data of member being overridden, if available
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* @param {*} value property value
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* @param {string} name property name
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*/
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function validateMethod( keywords, prev_data, value, name )
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{
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var prev = ( prev_data ) ? prev_data.member : null,
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prev_keywords = ( prev && prev.___$$keywords$$ )
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? prev.___$$keywords$$
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: {}
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;
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if ( keywords[ 'abstract' ] )
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{
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// do not permit private abstract methods (doesn't make sense, since
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// they cannot be inherited/overridden)
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if ( keywords[ 'private' ] )
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{
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throw TypeError(
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"Method '" + name + "' cannot be both private and abstract"
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);
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}
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// abstract final also does not make sense
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if ( keywords[ 'final' ] )
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{
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throw TypeError(
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"Method '" + name + "' cannot be both abstract and final"
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);
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}
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}
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// const doesn't make sense for methods; they're always immutable
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if ( keywords[ 'const' ] )
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{
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throw TypeError(
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"Cannot declare method '" + name + "' as constant; keyword is " +
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"redundant"
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);
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}
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// search for any previous instances of this member
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if ( prev )
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{
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// disallow overriding properties with methods
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if ( !( prev instanceof Function ) )
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{
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throw TypeError(
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"Cannot override property '" + name + "' with method"
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);
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}
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// final methods cannot be overridden
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if ( prev_keywords[ 'final' ] )
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{
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throw TypeError( "Cannot override final method '" + name + "'" );
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}
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// do not allow overriding concrete methods with abstract
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if ( keywords[ 'abstract' ] && !( util.isAbstractMethod( prev ) ) )
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{
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throw TypeError(
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"Cannot override concrete method '" + name + "' with " +
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"abstract method"
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);
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}
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// ensure parameter list is at least the length of its supertype
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if ( ( value.__length || value.length )
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< ( prev.__length || prev.length )
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)
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{
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throw TypeError(
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"Declaration of method '" + name + "' must be compatiable " +
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"with that of its supertype"
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);
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}
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// do not permit visibility de-escalation
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if ( prev_data.visibility < getVisibilityValue( keywords ) )
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{
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throw TypeError(
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"Cannot de-escalate visibility of method '" + name + "'"
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);
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}
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}
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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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// disallow overriding methods with properties
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if ( prev instanceof Function )
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{
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throw new TypeError(
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"Cannot override method '" + name + "' with property"
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);
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}
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// do not permit visibility de-escalation
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if ( prev && ( prev_data.visibility < getVisibilityValue( keywords ) ) )
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{
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throw TypeError(
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"Cannot de-escalate visibility of property '" + name + "'"
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);
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}
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// abstract properties do not make sense
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if ( keywords[ 'abstract' ] )
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{
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throw TypeError(
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"Property '" + name + "' cannot be declared as abstract"
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);
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}
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// nor do final properties, because of late static binding (const should be
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// used instead; read up on the rationale in the documentation)
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if ( keywords[ 'final' ] )
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{
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throw TypeError(
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"Property '" + name + "' cannot be declared as final; consider " +
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"const"
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);
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}
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if ( keywords[ 'static' ] && keywords[ 'const' ] )
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{
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throw TypeError(
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"Static keyword cannot be used with const for property '" +
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name + "'"
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);
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}
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getMemberVisibility( members, keywords )[ name ] = [ value, keywords ];
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};
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/**
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* Copies a getter 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 {*} value getter value
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*
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* @param {Object.<string,boolean>} keywords parsed keywords
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*
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* @return {undefined}
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*/
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exports.buildGetter = function( members, meta, name, value, keywords )
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{
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Object.defineProperty(
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getMemberVisibility( members, keywords ),
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name,
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{
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get: value,
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enumerable: true,
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// otherwise we can't add a setter to this
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configurable: true,
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}
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);
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};
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/**
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* Copies a 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 setter name
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* @param {*} value 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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* @return {undefined}
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*/
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exports.buildSetter = function( members, meta, name, value, keywords )
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{
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Object.defineProperty(
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getMemberVisibility( members, keywords ),
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name,
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{
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set: value,
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enumerable: true,
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// otherwise we can't add a getter to this
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configurable: true,
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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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* @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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*
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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 )
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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 of public, protected or private may be used"
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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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if ( member = members[ visibility[ i ] ][ name ] )
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{
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return {
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member: member,
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visibility: ( ( fallback ) ? 0 : i ),
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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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* 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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function overrideMethod( super_method, new_method, instCallback, cid )
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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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if ( new_method )
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{
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override = function()
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{
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var context = instCallback( this, cid ) || this,
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retval = undefined
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;
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// the _super property will contain the parent method (we don't
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// store the previous value for performance reasons and because,
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// during conventional use, it's completely unnecessary)
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context.__super = super_method;
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retval = new_method.apply( context, arguments );
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// prevent sneaky bastards from breaking encapsulation by stealing
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// method references (we set to undefined rather than deleting it
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// because deletion causes performance degradation within V8)
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context.__super = undefined;
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// if the value returned from the method was the context that we
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// passed in, return the actual instance (to ensure we do not break
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// encapsulation)
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if ( retval === context )
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{
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return this;
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}
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return retval;
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};
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}
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else
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{
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// we are defining a new method
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override = function()
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{
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var context = instCallback( this, cid ) || this,
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retval = undefined
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;
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// invoke the method
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retval = super_method.apply( context, arguments );
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// if the value returned from the method was the context that we
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// passed in, return the actual instance (to ensure we do not break
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// encapsulation)
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if ( retval === context )
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{
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return this;
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}
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return retval;
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};
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}
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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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( super_method.__length || super_method.length )
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);
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return override;
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}
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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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function getVisibilityValue( keywords )
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{
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if ( fallback )
|
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{
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// if we have to fall back, we don't support levels of visibility
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return 0;
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}
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else 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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