Why “gulp-jest” is failing with: “Please run node with the --harmony flag!”?

Question

I get the following error when running gulp test:

Error: Please run node with the --harmony flag!

Here is my gulp task:

var jest = require('gulp-jest');

gulp.task('test', function() {
  return gulp.src('src/**/__tests__').pipe(jest({
    rootDir: 'src',
    scriptPreprocessor: '../node_modules/6to5-jest',
    unmockedModulePathPatterns: [ 'react' ]
  }));
});

To reproduce: https://github.com/SEEK-Jobs/react-playground

Note that npm test works properly (test is failing as expected), but gulp test fails with the error above. Both npm test and gulp test have the same config object:

{
  rootDir: 'src',
  scriptPreprocessor: '../node_modules/6to5-jest',
  unmockedModulePathPatterns: [ 'react' ]
}

What am I doing wrong?

Answer 1

As far as I can tell the error is thrown from jest-cli.

The reason you don't get it with npm test is that you probably configured npm to run the jest bin script directly, which uses harmonize to programmatically set the --harmony flag.

You can fix by installing harmonize and putting require('harmonize')() in your gulpfile.

Answer 2

It was a bug in gulp-eslint, and it is fixed now in version 0.3.0.