114 lines
3.2 KiB
JavaScript
114 lines
3.2 KiB
JavaScript
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/**
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* Copyright 2017 Google Inc. All rights reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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const esprima = require('esprima');
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const ESTreeWalker = require('../ESTreeWalker');
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// This is converted from Babel's "transform-async-to-generator"
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// https://babeljs.io/docs/plugins/transform-async-to-generator/
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const asyncToGenerator = fn => {
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const gen = fn.call(this);
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return new Promise((resolve, reject) => {
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function step(key, arg) {
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let info, value;
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try {
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info = gen[key](arg);
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value = info.value;
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} catch (error) {
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reject(error);
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return;
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}
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if (info.done) {
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resolve(value);
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} else {
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return Promise.resolve(value).then(
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value => {
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step('next', value);
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},
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err => {
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step('throw', err);
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});
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}
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}
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return step('next');
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});
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};
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/**
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* @param {string} text
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*/
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function transformAsyncFunctions(text) {
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const edits = [];
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const ast = esprima.parseScript(text, {range: true});
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const walker = new ESTreeWalker(node => {
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if (node.type === 'FunctionExpression' || node.type === 'FunctionDeclaration' || node.type === 'ArrowFunctionExpression')
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onFunction(node);
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else if (node.type === 'AwaitExpression')
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onAwait(node);
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});
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walker.walk(ast);
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edits.sort((a, b) => b.from - a.from);
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for (const {replacement, from, to} of edits)
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text = text.substring(0, from) + replacement + text.substring(to);
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return text;
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/**
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* @param {ESTree.Node} node
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*/
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function onFunction(node) {
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if (!node.async) return;
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let range;
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if (node.parent.type === 'MethodDefinition')
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range = node.parent.range;
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else
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range = node.range;
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const index = text.substring(range[0], range[1]).indexOf('async') + range[0];
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insertText(index, index + 'async'.length, '/* async */');
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let before = `{return (${asyncToGenerator.toString()})(function*()`;
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let after = `);}`;
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if (node.body.type !== 'BlockStatement') {
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before += `{ return `;
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after = `; }` + after;
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}
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insertText(node.body.range[0], node.body.range[0], before);
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insertText(node.body.range[1], node.body.range[1], after);
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}
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/**
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* @param {ESTree.Node} node
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*/
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function onAwait(node) {
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const index = text.substring(node.range[0], node.range[1]).indexOf('await') + node.range[0];
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insertText(index, index + 'await'.length, '(yield');
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insertText(node.range[1], node.range[1], ')');
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}
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/**
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* @param {number} from
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* @param {number} to
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* @param {string} replacement
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*/
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function insertText(from, to, replacement) {
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edits.push({from, to, replacement});
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}
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}
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module.exports = transformAsyncFunctions;
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