74 lines
2.1 KiB
JavaScript
74 lines
2.1 KiB
JavaScript
/**
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* Copyright 2013-present, Facebook, Inc.
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* All rights reserved.
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*
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* This source code is licensed under the BSD-style license found in the
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* LICENSE file in the root directory of this source tree. An additional grant
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* of patent rights can be found in the PATENTS file in the same directory.
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*/
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/*jslint node:true*/
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/**
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* Desugars ES7 rest properties into ES5 object iteration.
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*/
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var Syntax = require('esprima-fb').Syntax;
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// TODO: This is a pretty massive helper, it should only be defined once, in the
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// transform's runtime environment. We don't currently have a runtime though.
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var restFunction =
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'(function(source, exclusion) {' +
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'var rest = {};' +
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'var hasOwn = Object.prototype.hasOwnProperty;' +
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'if (source == null) {' +
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'throw new TypeError();' +
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'}' +
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'for (var key in source) {' +
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'if (hasOwn.call(source, key) && !hasOwn.call(exclusion, key)) {' +
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'rest[key] = source[key];' +
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'}' +
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'}' +
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'return rest;' +
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'})';
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function getPropertyNames(properties) {
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var names = [];
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for (var i = 0; i < properties.length; i++) {
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var property = properties[i];
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if (property.type === Syntax.SpreadProperty) {
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continue;
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}
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if (property.type === Syntax.Identifier) {
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names.push(property.name);
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} else {
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names.push(property.key.name);
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}
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}
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return names;
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}
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function getRestFunctionCall(source, exclusion) {
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return restFunction + '(' + source + ',' + exclusion + ')';
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}
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function getSimpleShallowCopy(accessorExpression) {
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// This could be faster with 'Object.assign({}, ' + accessorExpression + ')'
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// but to unify code paths and avoid a ES6 dependency we use the same
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// helper as for the exclusion case.
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return getRestFunctionCall(accessorExpression, '{}');
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}
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function renderRestExpression(accessorExpression, excludedProperties) {
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var excludedNames = getPropertyNames(excludedProperties);
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if (!excludedNames.length) {
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return getSimpleShallowCopy(accessorExpression);
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}
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return getRestFunctionCall(
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accessorExpression,
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'{' + excludedNames.join(':1,') + ':1}'
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);
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}
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exports.renderRestExpression = renderRestExpression;
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