Gulp 4 .watch() doesn't update file modified time

What were you expecting to happen?

When I change and save partial scss file, gulp should update modified time of main scss file.

What actually happened?

css/
 ├ _external.scss
 └ main.scss
main.css
gulpfile.js

I edit and save _external.scss, created and updated main.css. But gulp doesn’t update modified time of main.css. When I change and save main.scss, gulp updates modified time of main.css.

In other words, gulp will not update modified time of main.css when I edit and save partial scss file. In this case, which is true, specifications or bugs?

Please post a sample of your gulpfile (preferably reduced to just the bit that’s not working)

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

gulp.task('style', function() {
  return gulp.src('css/main.scss')
    .pipe(sass())
    .pipe(gulp.dest('./'));
});

gulp.task('watch', function() {
  gulp.watch('css/**/*.scss', gulp.series('style'));
});

What version of gulp are you using?

4.0.0

What versions of npm and node are you using?

npm 6.1.0 node 8.9.3 10.5.0

[phated]

Currently, this is a feature of gulp 4 due to a limitation of node’s fs.Stat object. If you need mtime to change - you need to modify the mtime on the files in your pipeline.

If you’d like to help work on a solution for this - we have an open issue at https://github.com/gulpjs/vinyl/issues/105

[takamoso]

I’m using a gulp-touch-cmd plugin implemented in a similar way now.