'channel closed' on watch

[prencher]

Whenever webpack detects a change, the following happens:

Error: channel closed
    at ChildProcess.target.send (internal/child_process.js:540:16)
    at Object.send (C:\Projects\Aliso\node_modules\awesome-typescript-loader\src\checker\send.ts:24:35)
    at Checker.req (C:\Projects\Aliso\node_modules\awesome-typescript-loader\src\checker\checker.ts:87:21)
    at Checker.emitFile (C:\Projects\Aliso\node_modules\awesome-typescript-loader\src\checker\checker.ts:98:21)
    at transform (C:\Projects\Aliso\node_modules\awesome-typescript-loader\src\index.ts:106:29)
    at transformationFunction (C:\Projects\Aliso\node_modules\awesome-typescript-loader\src\index.ts:57:44)
    at compiler (C:\Projects\Aliso\node_modules\awesome-typescript-loader\src\index.ts:73:30)
    at Object.loader (C:\Projects\Aliso\node_modules\awesome-typescript-loader\src\index.ts:15:18)
    at LOADER_EXECUTION (C:\Projects\Aliso\node_modules\loader-runner\lib\LoaderRunner.js:114:14)
    at runSyncOrAsync (C:\Projects\Aliso\node_modules\loader-runner\lib\LoaderRunner.js:115:4)

This is with [email protected] with the simplest of configs:

const webpack = require('webpack');
const packageJson = require('./package.json');

module.exports = {
    entry: {
        app: './source/main.ts',
        vendor: Object.keys(packageJson['dependencies']),
    },
    output: {
        path: 'build',
        filename: '[name].js'
    },
    devtool: 'source-map',
    resolve: {
        extensions: ['.ts', '.tsx', '.js', '.jsx'],
    },
    module: {
        loaders: [
            { test: /\.json$/, loader: 'json-loader' },
            { test: /\.tsx?$/, loader: 'awesome-typescript-loader' },
        ]
    },
    plugins: [
        new webpack.optimize.CommonsChunkPlugin({ name: 'vendor', filename: 'vendor.js' })
    ],
};

[drywolf]

I'm experiencing the same problem when running webpack --watch with awesome-typescript-loader

at-loader version: 3.0.0-beta.9
webpack version: 2.1.0-beta.26

[FrozenPandaz]

I am also having this issue but only for a larger project.

[s-panferov]

Hello everybody. It's very hard to debug things on Windows if you don't have one (webpack doesn't play well with virtualized environments), so I will appreciate any help with debugging.

And it also will be helpful to know more about your environments:

1. OS version
2. NodeJS version
3. TypeScript version

[FrozenPandaz]

Sorry, here is my environment.

OS: Mac OS X El Capitan
Node: 6.9.1
Typescript: 2.1.1

[prencher]

Completely forgot to put that on the initial issue:

• Windows 10
• Node.js 6.9.1
• TypeScript 2.0.10
• Webpack 2.1.0-beta.27

[drywolf]

• Windows 10
• Nodejs 4.2.6
• TypeScript 2.1.0-dev.20161011
• Webpack 2.1.0-beta.26

[FrozenPandaz]

@s-panferov Has this info helped you reproduce the issue?

[zspecza]

I'm also experiencing this problem on the latest Webpack 2 / TypeScript 2 releases (on macOS Sierra - Node 6.x)

I'm not too experienced with child process handling but I think the cause is either that the child process dies too soon or doesn't die at all... These are usually the causes of the "channel closed" error. I've tried playing with hooking on to SIGHUP / SIGTERM / etc signals in checker/checker.ts, checker/runtime.ts and checker/send.ts to try and close the child process with a graceful shutdown but haven't had any luck - I'm afraid the extent of my knowledge in this area isn't of much use here :(

For reference:

• http://stackoverflow.com/questions/24110460/node-child-process-channel-closed-on-process-send
• https://www.exratione.com/2013/05/die-child-process-die/

[s-panferov]

@FrozenPandaz neither I can reproduce the issue for all this time, nor my colleagues which use the loader.

I think I need to add some debug logging.

[s-panferov]

Just published a new version with more error handling. Please try 3.0.0-beta.10 and report errors if any.

[zspecza]

@s-panferov Tried it with 3.0.0-beta.10, the stderr output is the same as before the update.

Error: channel closed
...

No other errors are being logged. ts-loader works, though.

It seems it has to do with webpack running multiple concurrent builds.

I put a reproducible case here: https://github.com/declandewet/awesome-ts-loader-bug

Just run npm run dev to start the webpack watcher, then change any .ts file in src/ to trigger an incremental build. You should see the channel closed error

[drywolf]

I can confirm that I am also getting the error only when I use multiple concurrent builds in webpack.config.js.
If I only export a single build config from webpack.config.js the problem does not occur.

[s-panferov]

@declandewet thanks for the example. I'll try to figure it out.

[s-panferov]

@declandewet thanks for the investigation.

I've found the main reason for that behavior. It's because atl fails to detect a --watch more in the latest webpack@beta and kills child processes after a first compilation.

I have several possibilities to fix this:

1. Introduce a webpack plugin to reliably detect --watch mode
2. Wait for an answer from here Detect --watch mode reliably  webpack/webpack#3460
3. Don't rely on --watch mode detection, but this will require webpack to wait every time until TypeScript finishes its compilation to mark build as finished in --watch mode.

[Delagen]

#304