I'm trying to run gulp to build my app like Rob Dodson explains here
在命令行中，如果我运行：
npm run build
我收到以下错误：
[20:50:55] Using gulpfile ~/path/to/gulpfile.js [20:50:55] Starting 'default'... Deleting build/ directory... [20:50:56] The following tasks did not complete: default [20:50:56] Did you forget to signal async completion?
似乎有一些任务描述为＆＃34; 信号异步完成？＆＃34;这是什么意思？我该怎么做？
但是，如果我在命令行运行以下命令：
gulp
我收到如下错误消息：
[23:40:57] Using gulpfile ~/path/to/gulpfile.js /usr/local/lib/node_modules/gulp/bin/gulp.js:129 gulpInst.start.apply(gulpInst, toRun); ^ TypeError: Cannot read property 'apply' of undefined at /usr/local/lib/node_modules/gulp/bin/gulp.js:129:19 at nextTickCallbackWith0Args (node.js:420:9) at process._tickCallback (node.js:349:13) at Function.Module.runMain (module.js:443:11) at startup (node.js:139:18) at node.js:968:3
为什么会出现不同的错误消息？这是否暗示了导致错误的原因是什么？如果是这样，它是什么？我该怎么做才能解决它？
I just copied the files package.json, polymer.json and gulpfile.js from the sample code Rob supplied here。然后我运行了npm install as this answer describes。
'use strict';
// Documentation on what goes into PolymerProject.
const path = require('path');
const gulp = require('gulp');
const mergeStream = require('merge-stream');
const del = require('del');
const polymerJsonPath = path.join(process.cwd(), 'polymer.json');
const polymerJSON = require(polymerJsonPath);
const polymer = require('polymer-build');
const polymerProject = new polymer.PolymerProject(polymerJSON);
const buildDirectory = 'build/bundled';
/**
* Waits for the given ReadableStream
*/
function waitFor(stream) {
return new Promise((resolve, reject) => {
stream.on('end', resolve);
stream.on('error', reject);
});
}
function build() {
return new Promise((resolve, reject) => {
// Okay, so first thing we do is clear the build
console.log(`Deleting build/ directory...`);
del([buildDirectory])
.then(_ => {
// Okay, now lets get your source files
let sourcesStream = polymerProject.sources()
// Oh, well do you want to minify stuff? Go for it!
// Here's how splitHtml & gulpif work
.pipe(polymerProject.splitHtml())
.pipe(gulpif(/\.js$/, uglify()))
.pipe(gulpif(/\.css$/, cssSlam()))
.pipe(gulpif(/\.html$/, htmlMinifier()))
.pipe(polymerProject.rejoinHtml());
// Okay now lets do the same to your dependencies
let depsStream = polymerProject.dependencies()
.pipe(polymerProject.splitHtml())
.pipe(gulpif(/\.js$/, uglify()))
.pipe(gulpif(/\.css$/, cssSlam()))
.pipe(gulpif(/\.html$/, htmlMinifier()))
.pipe(polymerProject.rejoinHtml());
// Okay, now lets merge them into a single build stream.
let buildStream = mergeStream(sourcesStream, depsStream)
.once('data', () => {
console.log('Analyzing build dependencies...');
});
// If you want bundling, do some bundling! Explain why?
buildStream = buildStream.pipe(polymerProject.bundler);
// If you want to add prefetch links, do it! Explain why?
// buildStream = buildStream.pipe(new PrefetchTransform(polymerProject));
// Okay, time to pipe to the build directory
buildStream = buildStream.pipe(gulp.dest(buildDirectory));
// waitFor the buildStream to complete
return waitFor(buildStream);
})
.then(_ => {
// You did it!
console.log('Build complete!');
resolve();
});
});
}
gulp.task('default', build);
答案 0 :(得分：1)
原始错误与“备用错误”无关。
虽然build task runs gulp，npm run在系统安装gulp之前优先考虑本地安装的node_modules/.bin/gulp（gulp）。自己运行gulp（没有npm run）会调用全局安装的gulp，如果它与您的项目不兼容，可能会导致错误（例如，Gulp 3二进制文件与Gulp 4 API）你的脚本，似乎是这种情况）。您可以安装Gulp 4，以便自己运行gulp，或继续使用npm run build。
要解决原始错误，我建议从Polycast's original source（如果您还没有）开始，以确定可能存在的差异。
如果您更喜欢坚持当前的曲目，我建议您做一些事情：
polymer-build issue 88）。运行polymer build -v（详细构建）可能会有所帮助。buildStream.on('error', (err) => console.log(err))之后添加let buildStream = ...，以防在该流中出现任何未解压缩的error个事件。答案 1 :(得分：1)
我建议您使用新版本的PSK Custom Build：
https://github.com/PolymerElements/generator-polymer-init-custom-build/
已更新gulpfile.js。
答案 2 :(得分：0)
问题是由错误的导入路径引起的。
路径错误<link rel="import" href="../../../bower_components/polymer/polymer.html">
<link rel="import" href="../../bower_components/polymer/polymer.html">
正如@ tony19所描述的那样，错误的导入路径导致了无声失败。
我通过追求@abdonrd建议的路径找到了这个。 I followed the instructions here as follows
首先，我复制了我的项目。然后按照下面描述的过程加载到my-app目录中。
npm install -g polymer-cli
npm install -g generator-polymer-init-custom-build
mkdir my-app
cd my-app
polymer init custom-build
polymer build -v # the results of this command highlighted my error in red
错误显示了丢失文件的路径。我注意到它位于比应有的高一级，因为路径中缺少根目录my-app/。然后我不得不使用搜索字符串polymer/polymer.html手动搜索所有文件，直到我发现导入路径中的../数量（本例中为3）与深入的文件夹数量不匹配导入文件的根目录（本例中为2）。
在我更正文件路径后，我再次运行：
polymer build -v # building the project again, correctly this time
polymer serve build/bundled # to test serve the build/bundled version