如何在 gulp 中显示 webpack 错误

Question

I have a TypeScript project that is transpiled with webpack, and the build tasks are driven by gulp. Take this simple task to demonstrate my question:

var webpack = require('webpack');
var webpackStream = require("webpack-stream");

gulp.task("check", function() {
        return gulp.src("*")
            .pipe(webpackStream(require("./webpack.config.js"), webpack))
            .pipe(gulp.dest(OUTPUT_DIR));
    }
);

Now when all is well, gulp check works fine. Now suppose I made some coding error - this gulp task would emit:

[10:20:02] Starting 'check'...
[hardsource:chrome] Tracking node dependencies with: yarn.lock.
[hardsource:chrome] Reading from cache chrome...
(node:20232) UnhandledPromiseRejectionWarning
(node:20232) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:20232) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
[10:20:08] The following tasks did not complete: check
[10:20:08] Did you forget to signal async completion?

Which is very uninformative. If I remove .pipe(gulp.dest(OUTPUT_DIR)); from the check task, I get the original error message. For example:

[10:35:42] Starting 'check'...
[hardsource:chrome] Tracking node dependencies with: yarn.lock.
[hardsource:chrome] Reading from cache chrome...
[10:35:48] 'check' errored after 5.96 s
[10:35:48] Error in plugin "webpack-stream"
Message:
    ./myfile.ts
Module build failed: Error: Typescript emitted no output for C:\Projects\myfile.ts.
    at successLoader (C:\Projects\***\node_modules\ts-loader\dist\index.js:41:15)
    at Object.loader (C:\Projects\***\node_modules\ts-loader\dist\index.js:21:12)
 @ ./src/background/background.ts 16:25-54
 @ multi ./src/background/backgroundC:\Projects\***\src\myfile.ts
./src/myfile.ts
[tsl] ERROR in C:\Projects\***\src\myfile.ts(305,28)
      TS2345: Argument of type 'number | undefined' is not assignable to parameter of type 'number'.
  Type 'undefined' is not assignable to type 'number'.
Details:
    domainEmitter: [object Object]
    domain: [object Object]
    domainThrown: false

Adding pipes to gulp-load-plugins.logger either before or after the webpackStream doesn't help. Can I pipe the gulp stream to a gulp.dest, and still get the informative webpack error messages? How?

Answer 1

I had this happen even without hard-source-webpack-plugin . It seems to be a problem with webpack-stream itself: https://github.com/shama/webpack-stream/issues/34

Instead of:

.pipe(webpackStream(require("./webpack.config.js"), webpack))
.pipe(gulp.dest(OUTPUT_DIR));

Add an error handler to the webpackStream pipe:

.pipe(webpackStream(require("./webpack.config.js"), webpack))
    .on('error',function (err) {
      console.error('WEBPACK ERROR', err);
      this.emit('end'); // Don't stop the rest of the task
    })
.pipe(gulp.dest(OUTPUT_DIR));

Answer 2

I'm posting the solution instead of deleting the question, in case it's of use to someone in the future.

In our case the problem turned out to be usage of a webpack build accelerator called hard-source-webpack-plugin . Apparently it's a known issue - and the github link includes a potential workaround.