101 lines
2.9 KiB
JavaScript
101 lines
2.9 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 ES6 rest parameters into an ES3 arguments array.
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*
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* function printf(template, ...args) {
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* args.forEach(...);
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* }
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*
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* We could use `Array.prototype.slice.call`, but that usage of arguments causes
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* functions to be deoptimized in V8, so instead we use a for-loop.
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*
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* function printf(template) {
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* for (var args = [], $__0 = 1, $__1 = arguments.length; $__0 < $__1; $__0++)
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* args.push(arguments[$__0]);
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* args.forEach(...);
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* }
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*
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*/
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var Syntax = require('esprima-fb').Syntax;
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var utils = require('../src/utils');
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function _nodeIsFunctionWithRestParam(node) {
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return (node.type === Syntax.FunctionDeclaration
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|| node.type === Syntax.FunctionExpression
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|| node.type === Syntax.ArrowFunctionExpression)
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&& node.rest;
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}
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function visitFunctionParamsWithRestParam(traverse, node, path, state) {
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if (node.parametricType) {
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utils.catchup(node.parametricType.range[0], state);
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path.unshift(node);
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traverse(node.parametricType, path, state);
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path.shift();
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}
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// Render params.
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if (node.params.length) {
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path.unshift(node);
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traverse(node.params, path, state);
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path.shift();
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} else {
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// -3 is for ... of the rest.
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utils.catchup(node.rest.range[0] - 3, state);
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}
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utils.catchupWhiteSpace(node.rest.range[1], state);
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utils.catchup(node.body.range[0], state);
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path.unshift(node);
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traverse(node.body, path, state);
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path.shift();
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return false;
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}
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visitFunctionParamsWithRestParam.test = function(node, path, state) {
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return _nodeIsFunctionWithRestParam(node);
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};
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function renderRestParamSetup(functionNode, state) {
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var idx = state.localScope.tempVarIndex++;
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var len = state.localScope.tempVarIndex++;
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return 'for (var ' + functionNode.rest.name + '=[],' +
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utils.getTempVar(idx) + '=' + functionNode.params.length + ',' +
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utils.getTempVar(len) + '=arguments.length;' +
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utils.getTempVar(idx) + '<' + utils.getTempVar(len) + ';' +
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utils.getTempVar(idx) + '++) ' +
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functionNode.rest.name + '.push(arguments[' + utils.getTempVar(idx) + ']);';
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}
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function visitFunctionBodyWithRestParam(traverse, node, path, state) {
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utils.catchup(node.range[0] + 1, state);
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var parentNode = path[0];
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utils.append(renderRestParamSetup(parentNode, state), state);
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return true;
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}
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visitFunctionBodyWithRestParam.test = function(node, path, state) {
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return node.type === Syntax.BlockStatement
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&& _nodeIsFunctionWithRestParam(path[0]);
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};
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exports.renderRestParamSetup = renderRestParamSetup;
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exports.visitorList = [
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visitFunctionParamsWithRestParam,
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visitFunctionBodyWithRestParam
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];
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